meeting 3 laboratory diagnosis & the immune system

Meeting 3Meeting 3Laboratory Diagnosis & the Laboratory Diagnosis & the

Immune SystemImmune System

18 July 200918 July 2009

Culture and IdentificationCulture and Identification URINEURINE

Grid method-inoculation using a calibrated loop (1 ul)Grid method-inoculation using a calibrated loop (1 ul) No. of colonies = CFU/mlNo. of colonies = CFU/ml Results:Results:

• <10,000 CFU/ml = junk<10,000 CFU/ml = junk• Work-up >10,000 CFU/ml coloniesWork-up >10,000 CFU/ml colonies

STOOLSTOOL Multiple interrruptedMultiple interrrupted GN is planted to SSAGN is planted to SSA 1+, 2+, 3+ 4+1+, 2+, 3+ 4+ To look for the following:To look for the following:

• Non lactose fermenters, non-sorbitol fermentersNon lactose fermenters, non-sorbitol fermenters• Significant also:<in predominance>:Significant also:<in predominance>:

YeastYeast Staphylococcus aureusStaphylococcus aureus Salmonella, Shigella, Vibrio, Yersinia, CampylobacterSalmonella, Shigella, Vibrio, Yersinia, Campylobacter

Culture and IdentificationCulture and Identification RESPIRATORY TRACTRESPIRATORY TRACT

Multiple interruptedMultiple interrupted 1+, 2+, 3+ 4+1+, 2+, 3+ 4+ To look for the following:To look for the following:

• Streptococcus pyogenesStreptococcus pyogenes• Significant also:<in predominance>:Significant also:<in predominance>:

YeastYeast Staphylococcus aureusStaphylococcus aureus Haemophilus influenzae, Streptococcus pneumoniaeHaemophilus influenzae, Streptococcus pneumoniae Gram negative rods, Neisseria meningitidisGram negative rods, Neisseria meningitidis

GENITAL TRACTGENITAL TRACT Multiple interrruptedMultiple interrrupted 1+, 2+, 3+ 4+1+, 2+, 3+ 4+ To look for the following:To look for the following:

• Neisseria gonorrheaeNeisseria gonorrheae• Significant also:<in predominance>:Significant also:<in predominance>:

YeastYeast Staphylococcus aureusStaphylococcus aureus Gram negative rodsGram negative rods

Culture and IdentificationCulture and Identification Catheter tipCatheter tip

Planted (rolled) in SBAPPlanted (rolled) in SBAP Gram stain not requiredGram stain not required Work-up more than 15 colonies onlyWork-up more than 15 colonies only

Other SpecimensOther Specimens Multiple interruptedMultiple interrupted 1+, 2+, 3+ 4+1+, 2+, 3+ 4+ Work-up all organismsWork-up all organisms More than 3 organisms: questionable significanceMore than 3 organisms: questionable significance

Critical Values – Require Critical Values – Require notificationnotification

Positive AFB culture and stainPositive AFB culture and stain Positive Blood CulturePositive Blood Culture Positive Sterile Body FluidPositive Sterile Body Fluid Positive urine for the following:Positive urine for the following:

Streptococcus agalactiaeStreptococcus agalactiae Staphylococcus saprophyticusStaphylococcus saprophyticus

CULTURE AND CULTURE AND IDENTIFICATIONIDENTIFICATION

WORK-UPWORK-UP Use of biochemical testsUse of biochemical tests

• Tube (traditional) e.g. IMVICTube (traditional) e.g. IMVIC• Identification disksIdentification disks• AutomationAutomation


WORK-UPWORK-UP Use of polyvalent typing (anti-Use of polyvalent typing (anti-

serum)serum)


WORK-UPWORK-UP Observe for hemolytic patternsObserve for hemolytic patterns

• Beta-hemolysisBeta-hemolysis indicates a zone of indicates a zone of clearing in the blood agar in the area clearing in the blood agar in the area surrounding a bacterial colonysurrounding a bacterial colony

• Alpha-hemolysisAlpha-hemolysis is a greenish is a greenish discoloration of the blood agar discoloration of the blood agar surrounding a bacterial colonysurrounding a bacterial colony

• Gamma-hemolysisGamma-hemolysis is actually a lack of is actually a lack of hemolysis in the area surrounding a hemolysis in the area surrounding a bacterial colony growing on blood agarbacterial colony growing on blood agar

NON-CULTURAL METHODSNON-CULTURAL METHODS Immunological (antigen-antibody Immunological (antigen-antibody

reactions)reactions) AgglutinationAgglutination PrecipitationPrecipitation Neutralization TestsNeutralization Tests Opsonization & Complement Fixation Opsonization & Complement Fixation

TestsTests Use of cell cultureUse of cell culture Fatty Acid AnalysisFatty Acid Analysis Use of molecular biology toolsUse of molecular biology tools

• Nucleic Hybridization TestsNucleic Hybridization Tests• Polymerase Chain ReactionPolymerase Chain Reaction

Choice of Drugs Starts with Choice of Drugs Starts with Susceptibility Susceptibility

Susceptibility by itself does not assure Susceptibility by itself does not assure therapeutic successtherapeutic success

Lack of susceptibility guarantees Lack of susceptibility guarantees therapeutic failuretherapeutic failure

There are many other considerations in There are many other considerations in the choice of antibacterial drugsthe choice of antibacterial drugs Toxicity and side-effectsToxicity and side-effects Interactions with other drugsInteractions with other drugs Pharmacology of the drugPharmacology of the drug

Minimal Inhibitory ConcentrationMinimal Inhibitory Concentration

MICMIC Lowest concentration of antibiotic that Lowest concentration of antibiotic that

prevents visible growthprevents visible growth Broth or tube dilution methodBroth or tube dilution method

Serial 2-fold dilutions of the antibioticSerial 2-fold dilutions of the antibiotic Accurate but time-consumingAccurate but time-consuming

Disk sensitivity testDisk sensitivity test Rapid, but must be related to results from the Rapid, but must be related to results from the

tube dilution methodtube dilution method

g Antibiotic per ml 128 64 32 16 8 4 2 1 0.5

MIC

Tube Dilution Method for Determination of MIC

24 Hours

Disk Sensitivity Test

0 Time

Zone of Inhibition(mm in diameter)

128 64 32 16 8 4 2 1 0.5

Diameter of zone (mm)

4 8 12 16 20 24 28 32

MICg per ml) Tetracycline

Correlation of Zones of Inhibition and MIC

Amikacin

Minimal Bactericidal ConcentrationMinimal Bactericidal Concentration MBCMBC Lowest concentration of antibiotic that reduces Lowest concentration of antibiotic that reduces

the number of viable cells by at least 1000-foldthe number of viable cells by at least 1000-fold Performed in conjunction with MIC by the tube Performed in conjunction with MIC by the tube

dilution methoddilution method Aliquots from the tubes at and above the MIC are Aliquots from the tubes at and above the MIC are

plated onto agar mediaplated onto agar media The antibiotic is diluted, so that the remaining The antibiotic is diluted, so that the remaining

viable cells grow and form coloniesviable cells grow and form colonies The MBC of a truly bactericidal agent is equal to The MBC of a truly bactericidal agent is equal to

or just slightly above its MICor just slightly above its MIC

g Antibiotic per ml

128 64 32 16 8 4 2 1 0.5

MIC

Tube Dilution Method for Determination of MBC

MBC

Attainable Level of AntibioticAttainable Level of Antibiotic Concentration that can be reached in the Concentration that can be reached in the

target tissue without toxic side effects target tissue without toxic side effects If the attainable level of an antibiotic is If the attainable level of an antibiotic is

greater than the MIC for at least 90% of greater than the MIC for at least 90% of the isolates, that species is considered the isolates, that species is considered susceptible to that antibioticsusceptible to that antibiotic

For serious infections, those odds may For serious infections, those odds may provide inadequate guidance for treatment provide inadequate guidance for treatment

Trough Levels of AntibioticsTrough Levels of Antibiotics Levels of antibiotics reach minimal levels Levels of antibiotics reach minimal levels

(troughs) at roughly predictable times after (troughs) at roughly predictable times after administrationadministration

The troughs may be at or below the MICThe troughs may be at or below the MIC This may or may not be a problem because This may or may not be a problem because

of two mitigating factorsof two mitigating factors Post Antibiotic Effect, a prolonged period before Post Antibiotic Effect, a prolonged period before

bacteria resume growthbacteria resume growth Synergism between host defenses and sub- Synergism between host defenses and sub-

MIC levels of antibioticsMIC levels of antibiotics

Trough Levels of AntibioticsTrough Levels of Antibiotics Trough levels may increase the frequency Trough levels may increase the frequency

of drug-resistant bacteriaof drug-resistant bacteria Frequency of developing resistance is greatly Frequency of developing resistance is greatly

increased at levels just above the MICincreased at levels just above the MIC Development of resistance to ciprofloxacin is Development of resistance to ciprofloxacin is

10,000 times more frequent at 2 times the 10,000 times more frequent at 2 times the MIC compared to 8 times the MICMIC compared to 8 times the MIC

The Immune SystemThe Immune System

BLOODBLOOD A highly specialized tissue along with the A highly specialized tissue along with the

circulatory systemcirculatory system2 Phases2 Phases

1.1. LiquidLiquid– PlasmaPlasma

A complex mixture of proteins, electrolytes and A complex mixture of proteins, electrolytes and other chemical cpds dissolved in waterother chemical cpds dissolved in water

Transport, regulation of movement of water Transport, regulation of movement of water between the extravascular and intravascular fluid, between the extravascular and intravascular fluid, coagulation, immunoglobulins and inflammationcoagulation, immunoglobulins and inflammation

2.2. CellularCellular


2.2. CellularCellular Red blood cellsRed blood cells

Responsible for the transport of oxygen and carbon Responsible for the transport of oxygen and carbon dioxidedioxide

White Blood CellsWhite Blood Cells Participate in protecting the body from infectionParticipate in protecting the body from infection3 Kinds:3 Kinds:1.1. GranulocytesGranulocytes

NeutrophilsNeutrophils EosinophilsEosinophils BasophilsBasophils

2.2. AgranulocytesAgranulocytes LymphocytesLymphocytes MonocytesMonocytes

PlateletsPlatelets Functions in the coagulation processFunctions in the coagulation process

The Immune System: WBCsThe Immune System: WBCs

GranulocytesGranulocytes NeutrophilsNeutrophils

• Most abundant among the WBCsMost abundant among the WBCs• Participate in phagocytosisParticipate in phagocytosis

EosinophilsEosinophils• High count indicates parasitic infection or High count indicates parasitic infection or

allergic stateallergic state• CytotoxicCytotoxic

BasophilsBasophils• Act as mediator cells in allergy state Act as mediator cells in allergy state

increasing blood flow to the areaincreasing blood flow to the area


AgranulocytesAgranulocytes LymphocytesLymphocytes

• B cellsB cells Produces antibodiesProduces antibodies From the bone marrowFrom the bone marrow

• T cellsT cells Stimulates activities of other components of the Stimulates activities of other components of the

immune systemimmune system Several subsets:Several subsets:

• T helper cellsT helper cells• T suppressor cellsT suppressor cells• Cytotoxic cells Cytotoxic cells

• Natural Killer CellsNatural Killer Cells Do not require stimulationDo not require stimulation


AgranulocytesAgranulocytes MonocytesMonocytes

• Large phagocytic cells – macrophagesLarge phagocytic cells – macrophages• Examples:Examples:

Osteoclast: boneOsteoclast: bone Kupffer cells: liverKupffer cells: liver Microglia cell: brainMicroglia cell: brain Serosal macrophage:pleural cavitySerosal macrophage:pleural cavity Alveolar macrophage: lungAlveolar macrophage: lung

The Immune SystemThe Immune System EXTERNAL DEFENSESEXTERNAL DEFENSES

11stst line of defense line of defenseExamples:Examples:

• Anatomical barriersAnatomical barriers SkinSkin Mucous membranesMucous membranes

• Body secretions and excretionsBody secretions and excretions MucousMucous Tears, saliva, urine (wash actionTears, saliva, urine (wash action Lysozyme in tears/nose/salivaLysozyme in tears/nose/saliva Lactoperoxidase in breast milkLactoperoxidase in breast milk Acid pH in sweat, gastric juices, Acid pH in sweat, gastric juices, urine, urine,

Vaginal secretionsVaginal secretions Zn2+ and spermine in semenZn2+ and spermine in semen

• Normal commensal floraNormal commensal flora Inhibitory substancesInhibitory substances Competition for nutrientsCompetition for nutrients

Figure 2-4 part 1 of 2Figure 2-4 part 1 of 2Many barriers prevent pathogens from crossing epithelia and colonizing tissues.

Figure 2-4 part 2 of 2Figure 2-4 part 2 of 2Many barriers prevent pathogens from crossing epithelia and colonizing tissues.


INTERNAL DEFENSESINTERNAL DEFENSES Natural ImmunityNatural Immunity

• Non-specific, innate, rapidNon-specific, innate, rapid• Macrophage, neutrophilsMacrophage, neutrophils• Phagocytosis & inflammationPhagocytosis & inflammation

Adaptive ImmunityAdaptive Immunity• Specific, acquiredSpecific, acquired• LymphocytesLymphocytes• Hallmarks: specificity and memoryHallmarks: specificity and memory

MacrophagesMacrophages, a specific type of phagocyte, a specific type of phagocyte Can be found migrating through the bodyCan be found migrating through the body Can be found in various organs of the lymphatic Can be found in various organs of the lymphatic

systemsystem

Dendritic cellsDendritic cells Anti-bacterial defenseAnti-bacterial defense Antigen presentationAntigen presentation

Eosinophils Eosinophils – defense against parasites – defense against parasites

Internal Cellular and Chemical Internal Cellular and Chemical DefensesDefenses

Internal cellular defensesInternal cellular defenses Depend mainly on Depend mainly on phagocytosisphagocytosis

Phagocytes, types of white blood cellsPhagocytes, types of white blood cells Ingest invading microorganismsIngest invading microorganisms Initiate the inflammatory responseInitiate the inflammatory response

3m

Phagocytic CellsPhagocytic Cells Phagocytes attach to their prey via surface receptorsPhagocytes attach to their prey via surface receptors

And engulf them, forming a vacuole that fuses with a And engulf them, forming a vacuole that fuses with a lysosomelysosome

Pseudopodiasurroundmicrobes.

1

Microbesare engulfedinto cell.

2

Vacuolecontainingmicrobesforms.

3

Vacuoleand lysosomefuse.

4

Toxiccompoundsand lysosomalenzymesdestroy microbes.

5

Microbialdebris isreleased byexocytosis.

6

Microbes

MACROPHAGE

Vacuole Lysosomecontainingenzymes

The Immune System: NaturalThe Immune System: Natural

PHAGOCYTOSISPHAGOCYTOSIS Process describing the engulfment and Process describing the engulfment and

destruction of invading bacteria, viruses etc.destruction of invading bacteria, viruses etc. Steps:Steps:

AttractionAttraction Recognition and attachmentRecognition and attachment EndocytosisEndocytosis Phagosome-lysosome fusionPhagosome-lysosome fusion KillingKilling DigestionDigestion

The characteristic pus of a bacterial abscess The characteristic pus of a bacterial abscess is composed largely of decomposed PMNis composed largely of decomposed PMN

PhagocytosisPhagocytosis Neutrophil phagocytosis of Neutrophil phagocytosis of

Streptococcus pyogenesStreptococcus pyogenes. . White blood cells engulf White blood cells engulf many types of pathogenic many types of pathogenic bacteria, which induce an bacteria, which induce an apoptotic cascade that may apoptotic cascade that may aid in resolution of the aid in resolution of the infection. Paradoxically, S. infection. Paradoxically, S. pyogenes also causes pyogenes also causes white blood cell necrosis, white blood cell necrosis, which may contribute to which may contribute to pathogen survival and pathogen survival and disease.disease.

The Immune System: INFLAMMATIONThe Immune System: INFLAMMATION

ComponentsComponents1.1. PhagocytesPhagocytes Ingestion and destroys microbesIngestion and destroys microbes2.2. Complement SystemComplement System Attracts phagocytes to site of infectionAttracts phagocytes to site of infection3. Coagulation system3. Coagulation system Increases blood and fluid flow to site of infection; Increases blood and fluid flow to site of infection;

formation of walls to physically inhibit spread of formation of walls to physically inhibit spread of microorganismmicroorganism

4.4. CytokinesCytokines Enhancement of activitiesEnhancement of activities

Antimicrobial Proteins – Chemical Antimicrobial Proteins – Chemical DefenseDefense

Numerous proteins function in innate defenseNumerous proteins function in innate defense By attacking microbes directly of by impeding their By attacking microbes directly of by impeding their

reproductionreproduction About 30 proteins make up the About 30 proteins make up the complement complement

systemsystem Which can cause lysis of invading cells and help trigger Which can cause lysis of invading cells and help trigger

inflammationinflammation InterferonsInterferons

Provide innate Provide innate defense against virusesdefense against viruses and help and help activate macrophagesactivate macrophages

Inflammatory ResponseInflammatory Response

In local inflammation, In local inflammation, histaminehistamine and other and other chemicals released from injured cellschemicals released from injured cells Promote changes in blood vessels that allow Promote changes in blood vessels that allow

more fluid, more phagocytes, and antimicrobial more fluid, more phagocytes, and antimicrobial proteins to enter the tissuesproteins to enter the tissues

Redness, heat, and swelling around wound Redness, heat, and swelling around wound sitessites

Fever induction from the activated Fever induction from the activated macrophages – Severe case: septic shockmacrophages – Severe case: septic shock

Major events in the local inflammatory Major events in the local inflammatory responseresponse

Pathogen Pin

Macrophage

Chemical signals

Capillary

Phagocytic cells

Red blood cell

Bloodclottingelements

Blood clot

Phagocytosis

Fluid, antimicrobial proteins, and clotting elements move from the blood to the site.Clotting begins.

2Chemical signals released by activated macrophages and mast cells at the injury site cause nearby capillaries to widen and become more permeable.

1 Chemokines released by various kinds of cells attract more phagocytic cells from the bloodto the injury site.

3 Neutrophils and macrophagesphagocytose pathogens and cell debris at the site, and the tissue heals.

4

The Immune System: INFLAMMATIONThe Immune System: INFLAMMATION CARDINAL SIGNSCARDINAL SIGNS

CALOR (heat)CALOR (heat) Increased blood flow and release of soluble mediatorsIncreased blood flow and release of soluble mediators

RUBOR (redness)RUBOR (redness) Vasodilation and increased blood flowVasodilation and increased blood flow

TUMOR (swelling)TUMOR (swelling) VasodilationVasodilation Extravasation of fluid (permeability)Extravasation of fluid (permeability) Cellular influx (chemotaxis)Cellular influx (chemotaxis)

DOLOR (pain)DOLOR (pain) Release of soluble mediatorsRelease of soluble mediators Extravasation of fluidExtravasation of fluid Cellular influxCellular influx

INFLAMMATIONINFLAMMATION

Extensive necrosis of a body part is often called "gangrene" or gangrenous Extensive necrosis of a body part is often called "gangrene" or gangrenous necrosis. Seen here is the lower leg from a below the knee amputation. The necrosis. Seen here is the lower leg from a below the knee amputation. The affected skin is dark red to black and there is a large area of ulceration. affected skin is dark red to black and there is a large area of ulceration.

Concept 43.2: In acquired immunity, Concept 43.2: In acquired immunity, lymphocytes provide specific defenses lymphocytes provide specific defenses against infectionagainst infection

Acquired immunityAcquired immunity Is the body’s second major kind of defenseIs the body’s second major kind of defense Involves the activity of Involves the activity of lymphocyteslymphocytes Directly contact to pathogens or alerts from Directly contact to pathogens or alerts from

activated innate immunityactivated innate immunity


INTERNAL DEFENSESINTERNAL DEFENSES Natural ImmunityNatural Immunity

• Non-specific, innate, rapidNon-specific, innate, rapid• Macrophage, neutrophilsMacrophage, neutrophils• Phagocytosis & inflammationPhagocytosis & inflammation

Adaptive ImmunityAdaptive Immunity• Specific, acquiredSpecific, acquired• LymphocytesLymphocytes• Hallmarks: specificity and memoryHallmarks: specificity and memory

Antigen-binding sitesAntibody A

Antigen

Antibody BAntibody C

Epitopes(antigenicdeterminants)

An An antigenantigen is any foreign molecule is any foreign molecule That is specifically recognized by lymphocytes That is specifically recognized by lymphocytes

and elicits a response from themand elicits a response from them A lymphocyte actually recognizes and bindsA lymphocyte actually recognizes and binds

To just a small, To just a small, accessible portionaccessible portion of the antigen of the antigen called an called an epitopeepitope

Figure 43.7

The Immune System: ADAPTIVEThe Immune System: ADAPTIVE TWO IMPORTANT PROPERTIESTWO IMPORTANT PROPERTIES

The specific immune system remembersThe specific immune system remembers It amplifies the protective mechanisms of natural immunityIt amplifies the protective mechanisms of natural immunity

TYPES BASED ON THE PROCESS THEY ARE STIMULATEDTYPES BASED ON THE PROCESS THEY ARE STIMULATED:: Active Immunity (induced)Active Immunity (induced)

The immunized individual plays an active role in responding to the antigenThe immunized individual plays an active role in responding to the antigen Natural – due to infection or exposureNatural – due to infection or exposure Artificial – vaccinationArtificial – vaccination

Passive Immunity (transferred)Passive Immunity (transferred) provides immediate, short-term protectionprovides immediate, short-term protection Is conferred naturally when IgG crosses the placenta from mother to fetus or when Is conferred naturally when IgG crosses the placenta from mother to fetus or when

IgA passes from mother to infant in breast milkIgA passes from mother to infant in breast milk Can be conferred artificially by injecting antibodies into a nonimmune personCan be conferred artificially by injecting antibodies into a nonimmune person

Natural – transplacental, colostrumNatural – transplacental, colostrum Artificial – injection of immune globulinArtificial – injection of immune globulin

The Immune System: ADAPTIVEThe Immune System: ADAPTIVE BASED ON THE COMPONENTS OF THE IMMUNE BASED ON THE COMPONENTS OF THE IMMUNE

SYSTEMSYSTEM Humoral ImmunityHumoral Immunity

Antibodies – B cellsAntibodies – B cells IgMIgM IgGIgG IgEIgE IgAIgA IgDIgD

Most effective against bacteria, their toxins and viruses before they Most effective against bacteria, their toxins and viruses before they enter the host cellsenter the host cells

Cell Mediated ImmunityCell Mediated Immunity T cellsT cells Major form of defense against viruses and bacteria that have invaded the cellsMajor form of defense against viruses and bacteria that have invaded the cells

The five classes of The five classes of immunoglobulinsimmunoglobulins

Figure 43.18

First Ig class produced after initial exposure to antigen; then its concentration in the blood declines

Most abundant Ig class in blood; also present in tissue fluids

Only Ig class that crosses placenta, thus conferring passive immunity on fetus

Promotes opsonization, neutralization, and agglutination of antigens; less effective in complement activation than IgM (see Figure 43.19)

Present in secretions such as tears, saliva, mucus, and breast milk

Triggers release from mast cells and basophils of histamine and other chemicals that cause allergic reactions (see Figure 43.20)

Present primarily on surface of naive B cells that havenot been exposed to antigens

IgM(pentamer)

IgG(monomer)

IgA(dimer)

IgE(monomer)

J chain

Secretorycomponent

J chain

Transmembraneregion

IgD(monomer)

Promotes neutralization and agglutination of antigens; very effective in complement activation (see Figure 43.19)

Provides localized defense of mucous membranes byagglutination and neutralization of antigens (seeFigure 43.19)

Presence in breast milk confers passive immunity onnursing infant

Acts as antigen receptor in antigen-stimulated proliferation and differentiation of B cells (clonal selection)

The Immune System: ADAPTIVEThe Immune System: ADAPTIVE TYPES BASED ON THE PROCESS THEY ARE TYPES BASED ON THE PROCESS THEY ARE

STIMULATEDSTIMULATED:: Active Immunity (induced)Active Immunity (induced)

The immunized individual plays an active role in responding to the The immunized individual plays an active role in responding to the antigenantigen Natural – due to infection or exposureNatural – due to infection or exposure Artificial - vaccinationArtificial - vaccination

Passive Immunity (transferred)Passive Immunity (transferred) provides immediate, short-term protectionprovides immediate, short-term protection Is conferred naturally when IgG crosses the placenta from mother Is conferred naturally when IgG crosses the placenta from mother

to fetus or when IgA passes from mother to infant in breast milkto fetus or when IgA passes from mother to infant in breast milk Can be conferred artificially by injecting antibodies into a Can be conferred artificially by injecting antibodies into a

nonimmune personnonimmune person Natural – transplacental, colostrumNatural – transplacental, colostrum Artificial – injection of immune globulinArtificial – injection of immune globulin

The Immune System: ADAPTIVEThe Immune System: ADAPTIVE

BASED ON THE COMPONENTS OF THE BASED ON THE COMPONENTS OF THE IMMUNE SYSTEMIMMUNE SYSTEM Humoral ImmunityHumoral Immunity

Antibodies – B cellsAntibodies – B cells IgMIgM IgGIgG IgEIgE IgAIgA IgDIgD

Most effective against bacteria, their toxins and viruses Most effective against bacteria, their toxins and viruses before they enter the host cellsbefore they enter the host cells

Cell Mediated ImmunityCell Mediated Immunity T cellsT cells Major form of defense against viruses and bacteria that have invaded the Major form of defense against viruses and bacteria that have invaded the

cellscells

Boosting your immune system upBoosting your immune system up

In the secondary immune responseIn the secondary immune response Memory cells facilitate a faster, more efficient responseMemory cells facilitate a faster, more efficient response

Ant

ibod

y co

ncen

tratio

n(a

rbitr

ary

units

)

104

103

102

101

100

0 7 14 21 28 35 42 49 56Time (days)Figure 43.13

Antibodiesto A

Antibodiesto B

Primaryresponse toantigen Aproduces anti-bodies to A

2Day 1: First exposure toantigen A

1 Day 28: Second exposureto antigen A; firstexposure to antigen B

3 Secondary response to anti-gen A produces antibodiesto A; primary response to anti-gen B produces antibodies to B

4

A summary of innate and acquired immunityA summary of innate and acquired immunity

INNATE IMMUNITY Rapid responses to a

broad range of microbes

ACQUIRED IMMUNITYSlower responses to

specific microbes

External defenses Internal defenses

Skin

Mucous membranes

Secretions

Phagocytic cells

Antimicrobial proteins

Inflammatory response

Natural killer cells

Humoral response(antibodies)

Cell-mediated response(cytotoxic lymphocytes)

Invadingmicrobes

(pathogens)

• A summary of innate and acquired immunity

ANTIGEN-ANTIBODY REACTIONS:ANTIGEN-ANTIBODY REACTIONS: SEROLOGY comes from the fact that serum, the liquid SEROLOGY comes from the fact that serum, the liquid

portion of the blood where antibodies are found is used portion of the blood where antibodies are found is used in testing. in testing.

Serologic testing may be used in the clinical laboratory in Serologic testing may be used in the clinical laboratory in two distinct ways: two distinct ways:

a. To identify unknown antigens (such as microorganisms). This is a. To identify unknown antigens (such as microorganisms). This is called direct serologic testing. Direct serologic testing uses a called direct serologic testing. Direct serologic testing uses a preparation known antibodies, called antiserum, to identify an unknown preparation known antibodies, called antiserum, to identify an unknown antigen such as a microorganism.antigen such as a microorganism.

b. To detect antibodies being made against a specific antigen in the b. To detect antibodies being made against a specific antigen in the patient's serum. This is called indirect serologic testing. Indirect patient's serum. This is called indirect serologic testing. Indirect serologic testing is the procedure by which antibodies in a person's serologic testing is the procedure by which antibodies in a person's serum being made by that individual against an antigen associated with serum being made by that individual against an antigen associated with a particular disease are detected using a known antigen. .a particular disease are detected using a known antigen. .

ANTIGEN-ANTIBODY REACTIONS:ANTIGEN-ANTIBODY REACTIONS: Agglutination Agglutination

Known antiserum causes bacteria or other particulate antigens to clump Known antiserum causes bacteria or other particulate antigens to clump together or agglutinate. Molecular-sized antigens can be detected by together or agglutinate. Molecular-sized antigens can be detected by attaching the known antibodies to larger, insoluble particles such as latex attaching the known antibodies to larger, insoluble particles such as latex particles or red blood cells in order to makE the agglutination visible to particles or red blood cells in order to makE the agglutination visible to the naked eye. the naked eye.

ANTIGEN-ANTIBODY REACTIONS:ANTIGEN-ANTIBODY REACTIONS:

Precipitation Precipitation Known antiserum is mixed with soluble test antigen and a cloudy precipitate forms Known antiserum is mixed with soluble test antigen and a cloudy precipitate forms

at the zone of optimum antigen-antibody proportion. at the zone of optimum antigen-antibody proportion.

Complement-fixation Complement-fixation

ANTIGEN-ANTIBODY ANTIGEN-ANTIBODY REACTIONS:REACTIONS:

Enzyme-linked immunosorbent Enzyme-linked immunosorbent assay or ELISA assay or ELISA

ANTIGEN-ANTIBODY REACTIONS:ANTIGEN-ANTIBODY REACTIONS:Fluorescent antibody technique Fluorescent antibody technique A fluorescent dye is chemically attached to the known antibodies. A fluorescent dye is chemically attached to the known antibodies.

When the fluorescent antibody reacts with the antigen, the antigen When the fluorescent antibody reacts with the antigen, the antigen will fluoresce when viewed with a fluorescent microscope. will fluoresce when viewed with a fluorescent microscope.

Microorganism – Host InteractionMicroorganism – Host Interaction

PORTAL OF EXIT

Long Quiz – Jul 25 8amLong Quiz – Jul 25 8amVirulence factors – Aug 1Virulence factors – Aug 1

meeting 3 laboratory diagnosis & the immune system

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