self, intentionality, and immunological explanation

doi: 10.1006/smim.2000.0238, available online at http://www.idealibrary.com onseminars in IMMUNOLOGY, Vol. 12, 2000: pp. 249256

Self, intentionality, and immunological explanation

Moira Howes

In this paper I propose that there are a number of con-ceptual reasons to preserve self-concepts in immunology.First, I contend that immunological language, includingself-terminology, is neither genuinely anthropomorphic, norperniciously teleological. Furthermore, although teleologyassociated with future-directed purposive intent is clearlyinappropriate in biological contexts, a special type ofteleology, intentionality-as-aboutness, needs to be presentif there is to be functional explanation in immunology.Second, based on an analogy with the human self, a selfcomprised of both non-specific innate functions and somaticself-representation, I claim that self-terminology is veryappropriate in immunological contexts. Finally, given theappropriateness of self-concepts in immunology, I suggestthat the most satisfactory conceptual structure for self-nonselfdiscrimination probably includes both innate and somaticmechanisms.

Key words: explanation / function / immunology / inten-tionality / teleology

c 2000 Academic Press

Introduction

Silverstein and Rose claim that some of the termi-nology used in immunology concerning self-nonselfdiscrimination, immunity, and immunopathology iseither impermissibly teleological or involves unwar-ranted anthropomorphism.1 Both of these claimsneed to be looked at more closely for two reasons.First, the issue of teleology and anthropomorphismin immunology is more complex than representedby Silverstein and Rose, and the elimination of tele-

From the Department of Philosophy, University at Buffalo, The StateUniversity of New York, Buffalo, NY 14260, USA.

c2000 Academic Press10445323/00/030249+ 08/$35.00/0

ological and anthropomorphic sounding languagemay be neither possible nor desirable. There ismore than one way to be teleological, and the kindthat is pernicious in biology, the kind that involvesconscious or intentional design, is only one of theseways. Second, examining a non-pernicious form ofteleological explanation can help us to figure outhow and why the self-concept is used in immunol-ogy and may help to clarify conflicts concerningits place in immunological reasoning. The debatein philosophy of biology concerning the place ofteleology in biology has not been decided. So ratherthan offer a definitive verdict, my objective is to showwhat conceptual role teleology may serve and how itrelates to the question of the immunological self.

In this paper, I first argue that the use of intentionalterms in immunology is not anthropomorphic. Thisopens the way for a different understanding ofintentionality, one that is tied to a non-perniciousform of teleological explanation. Second, I arguethis non-pernicious teleology is needed if immunefunction is to be understood. This in turn suggests,I claim, that the self-concept is a non-expendablecomponent of immunological explanation, generallyspeaking. Finally, assuming for the sake of argumentthat immunologists wish to retain the self-concept,I will set forth what I think is the best way toconceptualize this self.

Intentional terms and anthropomorphism

Intentional terms used to talk about immune func-tion, like those of recognize and discriminate areterms that seem to ascribe some kind of intermediarysubjective state to the immune system, a state whichexists prior to the immune systems action. Clearly, toascribe subjective states to the immune system is an-thropomorphic: it suggests that the immune system issomehow conscious of what it is doing. It is equallyclear that this is a view no one should hold and thetruth of this is not likely to be disputed by anyone.

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The question, then, might be whether or not the useof intentional terminology entails the ascription, un-wittingly perhaps, of conscious states, beliefs, and de-sires to the immune system. In other words, are immu-nologists just being imprudent, from the standpointof biology, is using these terms and risking these con-notations?

Some argue that intentional terminology may beuseful when the biochemical interactions involvedare not fully understood or known. Thus, immu-nologists are not really ascribing conscious stateswhen they use the terms, but rather using them asshorthand ways of saying we do not quite knowwhat is going on here yet. Once a biochemicalmechanism is fully known, a non-intentional accountcan be supplied. This view is supported by philoso-phers such as Melander who says that, immunologyhas already taken the first steps towards a purelychemical and non-intentional characterization of theimmune systems capacity to distinguish self fromnonself (Reference 2, p. 239). Presumably, then,the intentional terms used are just metaphors. Theymay have heuristic value insofar as they stimulatescientific reasoning, or confuse matters insofar asthey do not (Reference 3, pp. 199200). If theseterms or metaphors have only heuristic value, andare not otherwise involved in immunological expla-nations, we can omit them as soon as purely chemicalformulations come along.

As a philosopher, however, I am quite interested inthe question of why all of the metaphors used in im-munology are intentional terms. Possibly, immunolo-gists could find other metaphors to use, ones that arenon-intentional. I have a hard time imagining whatthese metaphors would be: even lock-and-key interac-tions seem to imply some kind of intention. Nonethe-less, there may be some. The line I wish to investigatehere concerns whether there might be a third wayof understanding the use of intentional terms in im-munology, one that neither views intentional terms asattributing consciousness to the immune system, norholds that they are expendable.

Rosenberg argues that in dismissing intentionalterminology as mere metaphor, aspects of scientifictheory that are natural to science are ignored. Inten-tional terminology comes very naturally to scientistsand appears to be inevitable and unavoidable(Reference 4, p. 66). This, he claims, stands in needof explanation. As Rosenberg points out, intentionalterminology is generally used by biologists withoutany precaution of definition, nor with any caveatagainst taking it literally (Reference 4, p. 69). At first

glance, there seem to be two reasons for this. First,Rosenberg says that it is so obvious that these termsare not meant literally, scientists do not bother todraw attention to their non-literal nature. Second,scientists generally feel confident that a purely bio-chemical mechanism can be substituted for the term,if not now, then in the future. The reason the term isused is to avoid literal, complicated and unmanage-able mechanistic explanations. As Rosenberg pointsout, biologists are well aware that by selfish geneRichard Dawkins is not saying that genes literally havea subjective state of selfishness. Rather, selfishness isimplicitly redefined to refer to a behavioral state andbehavioral states need not involve a subjective state,or as Dawkins says, a psychology of motives, at all(Reference 5, pp. 45). Mohan Matthen and EdwinLevy put the point the following way:

the view that attributing intentionalstructures to non-sentient entities isanthropomorphic rests, we think, on themisconception that such structures aresomehow connected to consciousnessthat postulating intentionality in non-sentient entities rests on a metaphoricalassimilation of these entities to sentiententities (Reference 6, p. 371).

What is eliminated in the implicit redefinition ofintentional terms in science, then, is mentalistic, orconscious, intentionality. In the immune system thereare no conscious beliefs, desires, goals or motives andwhen immunologists use these terms they implicitlyempty them of intentionality.

So far this description of what occurs when biolo-gists use intentional terms fits quite well with the viewthat these terms are expendable metaphors. Rosen-berg, however, makes a further claim, one that sug-gests to me that intentional terms are neither expend-able nor do they require an imprudent belief in apsychology of motives. Rosenberg says of intentionalterms that

suitably redefined, it is no surprise thatthese terms function naturally and in-evitably in the description of molecular in-teractions. They have been implicitly tai-lored to this purpose. Intentional vocab-ulary, when pressed into biochemical ser-vice retains its teleological, functional im-plications for behavior, and this togetherwith the intricacy, the plasticity, and thevariability of the biochemical interactions

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is what makes for its appropriateness inthis context (Reference 4, p. 73).

What does it mean to say that stripped of mentalisticintentionality, intentional terms retain their teleologi-cal, functional implications for behavior? It can meanonly this: there is a way of thinking teleologically inbiology that involves neither subjective, conscious,psychological goals or desires to achieve some givenend, nor the notion of conscious intentional design.

The task, then, is to determine what is happeningwhen we posit intentional structures in non-sentiententities. How is intentionality in non-sentient entitiesdifferent from that in sentient ones? To answer thisquestion I will now turn to a brief examination of thenotion of teleology. Teleology, properly construed ina biological context, need not violate precepts of evo-lutionary theory concerning the absence of consciousdesign. I argue that it is this kind of teleology that ex-plains why intentional terms are doing more than act-ing as shorthand descriptions of biochemical mech-anisms, but less than teleological accounts which vi-olate evolutionary precepts. It explains why riddingimmunology of self and danger terminology, forexample, in order to avoid an impermissible teleol-ogy is an oversimplification that obscures matters. Fi-nally, the need for teleological frameworks for func-tional explanation provides a strong reason for retain-ing intentional terminology, although not, of course,uncritically.

Function, teleology andintentionality-as-aboutness

The somewhat awkward phrase intentionality-as-aboutness serves to label a kind of intentionality atwork in biological explanations. This intentionalityhas no mentalistic component: in a sense, intention-ality is here implicitly redefined much in the way thatselfish gene and immune recognition are. Thereason for keeping the notion of intentionality, eventhough it has no mentalistic component, rests onthe idea that unless a biological mechanism can beunderstood to be about something, it is not understood.If the biological mechanism you are studying cannotbe understood as being about something, what youhave is a collection of molecules, reactions andrelations and no way of telling what they are doing inany overall sense. Without knowing what a system isabout, it is difficult to distinguish between functionalprocesses and other concurrent, but non-functional,

causal processes.7 Teleology is introduced into theequation because of the need to explain biologicalprocesses in terms of what they are for. However, thisteleology is not the kind one finds when sentientpurposive agents set about achieving their goals.

This point can be illustrated by looking at the claimthat evolutionary history is what makes biologicalsystems teleological. Consider Ruth Millikans well-known notion of a proper function, a notion whichis intended to naturalize teleology and reduce it toevolutionary explanation. Adapting an example putforth by Mohan Matthen, a proper function can bedescribed in the following manner.

The immune system has defense against pathogenicbacteria as a proper function because:

1. This defense is a reproduction of some priorprocess that defended against pathogens.

2. We now have an immune system because thatprior process defended against pathogens.8

An example first introduced by A. G. Cairns-Smithis used by Mark Bedau, to illustrate that the aboveanalysis of function is not sufficient to explain howwe normally think of function.9 That is, as Matthencontends, proper functions do not properly alignwith vernacular functions. Suppose there is a typeof crystal, one variant of which will crystallize morerapidly and to a greater extent if it is exposed towater. If the water-sensitive and non-sensitive variantsare both present in a river, the water-sensitive variantswill come to dominate the population. Suppose alsothat given enough time, the water-sensitive variantswill proliferate to such an extent that a dam will becreated. According to Bedau, on Millikans accountwe can say that the water- sensitive variant was selectedfor dam-making, and therefore dam-making would bea proper function of the crystal.

Crystals have dam-making as a proper functionbecause:

1. This dam-making is a reproduction of someprior process that led to dam-making.

2. We now have this dam-making process becausethat prior process led to dam-making.

It seems reasonable to say that the function of crystalshere stated is not a function as we normally think ofit; that is, it is a proper function, not a vernacularone. There just seems to be something wrong with thestatement crystals are selected for dam making, if bythis we mean that dam-making is a function of these

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crystals. Rather, dam-making seems to be somethingthat just happens: it is not a function of the crystals.Matthen says,

vernacular functions depend on howsomething is used, and not on causal ae-tiology. Function attributions seem to bedependent on user, role, mode of use, andthe utility that the user realizes from theoutcome. Further, function attributionsseem to be a matter of degree in such away that the perspective of the observeris relevant to how an absolute attributionis made. This also indicates that a pro-gram of reducing teleology to a scheme ofcausality present in the objective phenom-ena is misguided (Reference 8, p. 31).

In reducing teleology to mechanical causality,Matthen argues that what appears to be lost is alevel of description or analysis that is epistemo-logically necessary. We seem to need the notionof teleology, the notion that functions are aboutsomething, to understand those functions. Insteadof naturalizing teleology, Millikans account simplyuncouples selection and teleology and teleologydrops out of the equation. When teleology drops outof the equation, we are left with a type of functionalexplanation that cannot fully capture what is goingon in living systems. The idea that the function ofan immune response is to protect the organismcannot be captured in purely chemical terms. Whatis different about crystals and living organisms andthe functional explanations or analyses that applyto them is two-fold. First, living organisms bring inthe notion of a user and with it teleology. Second,an evaluative component is introduced insofar asthe perspective of the observer is relevant to thefunctional attribution made. As Ronald de Sousasays, functional explanations that do not incorporateteleology only work

insofar as we are not interested in theissue of what counts as an individual. Assoon as that issue is broached we cannotaltogether escape evaluative issues. Caseswhere such references to individualsseem inescapable include the case ofthe immune system as well as the case ofmentality (Reference 10, fn. p. 187).

And, furthermore:

the individuals we are interested in arenot just whatever units that science de-cides it can most conveniently understandthe world in terms of: we already havean antecedent sense of what units wewant to focus on. This is the evaluativeaspect of individuation. In the case ofthe immune system, whether somethingdoes or does not count as self is partlyan evaluative issue: there are good rea-sons, for example, to regard a cancerousgrowth as nonself rather than self, eventhough in some respects its developmentis an outcome of the organisms ownevolution (Reference 10, p. 205).

Silverstein and Rose wish to rid immunology of animpermissible teleology and unwarranted anthro-pomorphism. I argue that the teleology found inconscious design is not the kind that makes its wayinto explanations of immune function and further,that the anthropomorphism found in immunologyis not really anthropomorphism. Silverstein andRose themselves use intentional terminology andnon-pernicious teleology in trying to explain theirview of immune function. They use it when speakingof the law of unintended consequences and whenclaiming that a balance will be struck between thebenefit and cost at each step of the immune process(Reference 1, p. 3, 9). These claims depend on therebeing a user and a mode of use, and this in turnintroduces an evaluative component regarding thatuser. What captures the interest of a philosopher ofbiology is how teleological concepts involving usersand modes of use in biological explanation canbe understood naturalistically, that is, without in-corporating notions of consciously intended design.Millikans account might not be satisfactory, but thisdoes not preclude the possibility of there being otheraccounts, such as Matthens, which are.

What does this say about self-nonselfdiscrimination?

My argument thus far provides some justificationfor the continued use of teleological frameworksfor the analysis of the immune function. It alsosuggests that intentional terms like discriminatesare non-mentalistic and that they are important, in-tegral and acceptable components of immunologicaltheorizing. It seems clear that one must consider the

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organism in order to adequately analyze and describethe immune function. What is still problematic isthe use of the term self. The working definitionfor self-nonself discrimination outlined in the intro-duction to this seminar is that biodestructive activityhas to be regulated so that the host is not destroyedand the pathogen is. Others in this seminar areclearly concerned with the organism when structuringtheir explanations of what the immune system isdoing. Antnio Coutinho says that because natu-ral selection concerns whole organism behaviour,only observations pertaining to whole individuals,and not just those of isolated cells or molecules,should be considered with respect to self-nonselfdiscrimination. In vitro studies are thought to belacking because the meaning of effector functions, forexample, can only be read-out through the organismitself (Reference 11, p. 3). Rolf Zinkernagel pointsto the importance of asking whether observationsand their interpretations make evolutionary sense,since the driving evolutionary force of the immunesystem is protection of the host against pathologycaused by infections (Reference 12, p. 4). Zinker-nagel also says that self-nonself discrimination isobligatory for antigens in lymphoid systems. Here,the terms self and host are used interchangeably.Rod Langman and Melvin Cohn also use host andself interchangeably.13 The question that needs tobe answered here is why self need be used at all;perhaps the user needed in functional explanationsis simply the host. Why not just talk about host-pathogen discrimination? Is not self just implicitlyredefined to mean host anyway?

I claim that there are two reasons why using selfmay be preferable. The first reason is the weaker ofthe two. Consider the function of the liver, whichcontributes to the well being of the organism throughits metabolic activities. The function of the immunesystem is also to contribute to the well being of theorganism, at least insofar as it increases reproductivefitness. However, unlike the liver, its function isspecifically concerned with the organism-pathogenrelationship. Because the immune system has aspecial function set up to deal directly with theorganism-environment relationship, it is more akinin this respect to the nervous system than any otherorgan system in the body. Self-terminology may be away of implicitly acknowledging the specific functionsof the immune system that concern the relevant dif-ferences between an organism and its environment.However, one could still use the terms host andpathogen to describe this function specific to the

immune system. It may be that germline mechanismswhich serve to protect the host from pathogens canbe discussed in the context of organism-environmentrelations, and self-nonself relations need not beconsidered. Even so, Ruslan Medzhitov and CharlesJaneway say that the innate immune response topathogen-associated molecular patterns (PAMPs)distinguishes non-infectious self from infectious non-self, and does so with great accuracy (Reference 14,p. 6). This first reason, then, suggests (although notin the most convincing manner) that self terminologyis appropriate at the innate level.

A stronger reason for the retention of self terminol-ogy rests on the existence of somatic immunologicalmechanisms peculiar to certain organisms. Thesomatic mechanisms contributing to immune-systemfunction introduce a higher level of individuality andthis is where the use of self-terminology is mostappropriate. If an organisms immune system hasa specific mechanism of self-representation, it seemsappropriate to describe this system using self termi-nology. Organisms that have only an innate immunesystem, such as invertebrates, may not have suchsystems of representation; this being the case, theself term would not be appropriate in accounts ofinvertebrate immunology. Vertebrates, on the otherhand, might have varying degrees of representa-tion, and so varying degrees of immunological self.If the vertebrate immune system does engage inself-representation, and it seems that it does, thismaps nicely onto the way we divide up the animateworld according to conscious self-representation.We do not say that worms have selves. We mightsay cats have some kind of proto-self, if we likethem. We are comfortable with the idea that humanbeings have selves. Where the human self and thehuman organism begin and end remains a matter ofcontroversy: what seems clear is that many differentfunctions and systems go into the making of humanselfhood, right down to the more reptilian aspectsof our brains. What is distinctive about the humanself is that a higher system of self-representationis an integral part of our individuality, even thoughit is not solely responsible for that individuality. It is invirtue of somatic functions that are directed towardsself-representation that self, as opposed to host ororganism, is an appropriate term in psychology andneuroscience. The same could be said of the immunesystem. Whether the immune system actually engagesin self-representation is, of course, an empiricalmatter to be decided by immunologists.

The question I address next concerns how the self

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is to be conceptualized in immunology, assuming forthe sake of argument that immunologists wish toretain self-concepts in their explanations of immunefunction.

Conceptualizing selfhood

One of the assumptions that most derailed accountsof self-identity in analytic philosophy is the assump-tion that there must be one necessary and sufficientcriterion capable of accounting for the identity of theself over time. Such a criterion would actually definethe real self, a self that is persistent through time. Cou-pled with this assumption is another, one that is oftenconcealed from view. This is the assumption that thereal self must be discrete; that is, the real self mustbe definite, clearly bounded, distinctly separate fromnonself, and it must be resistant to change.

The real self, in this view, is like an anchor: itgrounds and maintains the self while physical andpsychological properties change. Both psychologicaland physical criteria have been proposed for such ananchor; however, these different criteria fail to pickout the same entity as the real self, that is, the criteriafail to coincide. This would be unproblematic if eitherpsychological or physical criteria could be shown tobe superior. The trouble is that these different criteriaare, generally speaking, equally compelling. They arealso equally problematic.

One might think an obvious solution to the failureof criteria to coincide would be to develop a criterioncomplexing both psychological and physical featuresof self. However, this cannot be done while still sat-isfying yet another requirement for self-identity overtime. This is the transitivity requirement of identityand it holds that if X is Y, and Y is Z, then X is Z. Thetransitivity requirement explains why philosophershave focused on developing criteria that are eitherexclusively psychological or exclusively physical. Acomplexed criterion, where X is psychological and Zis physical would violate transitivity.

A solution to the problem of the self in philosophypresents itself, as I have argued elsewhere, if we rejectthe following four assumptions. First, that the real selfis discrete and unchanging. Second, that there mustbe a necessary and sufficient criterion for the real self.Third, that transitivity must be satisfied. Fourth, thatpsychological and physical criteria must pick out pre-cisely the same entity as the real self.15 Next it has tobe shown how there can be a self in spite of the re-jection of these assumptions. While there is no room

to do this here, I claim that a modified self identitycan be maintained in virtue of overlapping sets of cri-teria, none of which are necessary and sufficient inthemselves to account for the self. Because the cri-teria overlap via functional relationships, a modifiedform of identity over time can be maintained. Such aself must be dynamic, not static. And, at any given mo-ment, the discreteness of the self is not possible, bothbecause an unclear boundary exists between self andother, functional relationships drawing upon both asthey do, and because evaluative considerations con-cerning individuality are inescapable.

Gaining acceptance for an indiscrete view of theself is not a simple task. The assumption that any realself must be discrete is a difficult one to dislodge.Nonetheless, an indiscrete view of the self has itsmerits, some of which are relevant to the situation inimmunology. A view of the human self as overlappingand multi-factorial makes the most sense given ouractual experience of self in the world. Psychologicalfeatures closely overlap with physical features. Al-though innate biological factors may not themselvesbe sufficient grounds from human selfhood, theycertainly inform and shape the self. Also, because offunctional inter-relationships, it may be difficult totease germline contributions from the higher specificfunctions directly responsible for self-representationand self-definition in human beings.

To show how the multi-factorial and overlappingnature of the self is relevant to immunology I willconsider examples taken from Irun Cohen, andLangman and Cohn respectively. Cohen says,

the healthy immune system recognizesboth self-antigens and foreign antigens,without class discrimination. Contraryto the assertion of Langman and Cohn,the job of the immune system is not toproduce a verdict distinguishing thatwhich is destroyed from that which isnot to be destroyed. The data suggestthat the immune system, in both itsgermline and somatic (adaptive) arms, iscontinuously busy recognizing the statesof tissues and responding to them withcorrective inflammation. Self-nonselfdiscrimination is not what the immunesystem is about. The immune system isabout fitness (Reference 16, p. 6).

Self-nonself discrimination may not be what the im-mune system is about in its entirety, but it is hard tothink it is irrelevant. Consider, for example, Jeffrey

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Stewarts hypothesis that systemic lupus erythemato-sus is related to female X-inactivation mosaicism.17

Clonal descendants of late blastula cells in femaleswill have the same X-inactivation as their progenitorsand this results in patches of tissue in which the cellshave the same X-inactivation. Stewart points to thelines of Blaschko in human beings and the color vari-ation found in calico cats as examples of patches ofcells having the same X-inactivation. Because the self-proteins expressed by these cells will also differ (be-cause the X-encoded genes will either be from themother or the father), Stewart reasons that if thesetwo-cell classes extend to the tolerizing cells of thethymus, some lymphocytes may only be rendered tol-erant to one of these two classes. The lymphocytesmay then be autoreactive to self-antigens of the othercell class. This might help explain why lupus dispro-portionately affects females. Stewart also points outthat linear scleroderma has been found, in some casesto follow the lines of Blaschko.18

Stewarts view here highlights why a mechanismresulting in the differential treatment of self tissuesmay be important. Cohen points to sclerodermaas an example of how the immune system may beconcerned with inflammation and healing and notself-nonself discrimination, scleroderma involvingthe inappropriate formation of scar tissue. In thisinstance, Cohen says that disease can result fromunregulated processes associated with healing, andnot only from the first killing of self-target cells(Reference 16, p. 5). It is unclear to me why unregu-lated processes associated with healing need excludeself-nonselfdiscrimination. If X-inactivation affectstolerization, this could be enough to upset the reg-ulation of natural autoimmunity, and consequently,self-maintenance. Why cannot all of these factors beinvolved in the immunological maintenance of self-nonself discrimination? There may be many routes,independent or otherwise, to scleroderma. However,perhaps Cohens view is more akin to the idea thatkilling self-target cells is not all that is involved, andthat the immune system will sort the situation out viasome sort of flexible self dialogue.

The benefits of a multi-factorial and overlappingapproach to selfhood in immunology might also bedemonstrated by looking more closely at the im-munology of pregnancy. Langman and Cohn say that

it remains an open question whether thefetus induces unresponsiveness in themother of the same type as the motherdevelops toward her own self-antigens,

or whether the fetus creates a privi-leged boundary for its relatively shortbut important invasion of the mother(Reference 13, p. 11).

This view seems to rest on there being two discreteselves: those of the mother and the fetus. But this dis-creteness has been challenged. Elizabeth Bonney andPolly Matzinger, for example, found that the motheris not continuously exposed to circulating fetal cellsand, in fact, has the capacity to eliminate themwithout eliminating the fetus (Reference 19, p. 40).Others suggest that maternal recognition for fetalantigens may be beneficial or necessary for a normalpregnancy (Reference 20, p. 383). Such findings can-not be accommodated if a strict self-nonself boundaryis thought necessary to prevent the rejection of thefetus. If maternal immune cells and fetal cells docome into contact, on the discrete view, one wouldthink the fetus would be rejected. Given that selfhoodin general is not, as far as I am concerned, a matterof discrete boundaries, I am suspicious of attemptsto use discreteness in determining relationshipsbetween biological organisms. This is particularlythe case in pregnancy, where our usual assumptionsabout selfhood in general are challenged. This doesnot mean that tolerance and special boundaries arenot involved in pregnancy, but that such mechanismsmay be only part of the story. It may be that thefetus is not rejected because it is not dangerous tothe mother, as Matzinger claims. It is possible thatthere are several routes to the maintenance of selfin both mother and fetus during pregnancy, somegermline-encoded, and some somatic. What mighthave to be given up is the idea that discriminatingself from nonself in a discrete fashion is necessaryand sufficient to account for the immune self.

I think Anderson and Matzinger provide the mostexplicit statement of the problem regarding the selfin immunology, and this accords with what I claimis the best way to conceptualize selfhood in general.The key to the problem seems to involve the claimthat the immunological decision about whether torespond is separate from the question of how theimmune system is to avoid destroying the tissues itis meant to protect when it responds. Anderson andMatzinger contend that,

the most important distinction betweenSNS models and the Danger model iswhether this definition is used to deter-mine whether a response will occur. Inthe Danger model, endogenous alarm

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signals govern that decision. Thus, selfneed not be ignored and non-self neednot always be fought. This distinctionallows for all of the following. First, thedefinition of self can change as the bodychanges, matures, procreates and growsold. Second, the definition is never final(Reference 21, p. 6).

This does not mean that tolerance to self is unim-portant. It does mean that a discrete separation ofself from nonself in immune function is not theentire basis of immunological self. As Anderson andMatzinger say,

the Danger model allows for a definitionof self that is dynamic and non-exclusive:a living, changing definition that allows usto come out of the cold war attitude ofus versus them to a new view of globalinterrelationships (Reference 21, p. 14).

Langman and Cohns view sets up a discretesorting of the world into self and nonself from theoutset. However, if the on/off switch is not basedon a discrete sorting (and perhaps even if it is), itseems unlikely that the immune function can beconceptualized under the rubric of discrete selfhood.This, however, does not mean there is no specificimmune function relating to self- representation andself-definition. As with the personal self, higher func-tions involving self-representation and self-definitioncan do the job without generating or relying upona discrete boundary between self and nonself. Itcan also do the job in concert with other functionsthat contribute to and shape selfhood, even thoughthese latter functions may make no representativedistinction between self and nonself at all. Therole of intentional terminology and non-perniciousteleology in immunology indicates that immunolog-ical explanations are well-served by self-concepts.Self-concepts may even be necessary to those expla-nations. The remaining question appears to be theempirical one: is there a system of self-representationin the immune system or not?

Acknowledgements

I would like to thank Wayne Myrvold, Departmentof Philosophy, The University of Western Ontario

and Rod Langman, Salk Institute, for their helpfulcomments and criticisms regarding earlier work. Ihave taken these comments into consideration here;however, it should not be assumed they would supportthe claims made in this paper.

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IntroductionIntentional terms and anthropomorphismFunction, teleology and intentionality-as-aboutnessWhat does this say about self-nonself discrimination?Conceptualizing selfhoodReferences

self, intentionality, and immunological explanation

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