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DISCREPANT EXPRESSION OF "ACTIVATION" ANTIGENS IN CORD BLOOD T LYMPHOCYTES, SUGGESTING SOME IMMATURITY OF T CELL IMMUNOREGULATORY CIRCUITS.

Toshio Miyawaki. Department of Pediatrics, School of Medicine, Kanazawa University, Kanazawa, 920, Japan.

In pokeweed mitogen (PWM)-stimulated co-culture system, OKT4 + T cells from adult peripheral blood exert help for B cell differentiation, whereas OKT4 + T cells from cord blood showed marked suppression. On stimulation with PWM, cord blood T cells showed negligible expression of Ia-like determinants on their surface, while ~ 40% of adult peripheral blood T cells expressed Ia- like determinants. These Ia + T cells belonged largely to OKT4 + subset and functionally, such Ia +, OKT4 + cells appeared to have a pivotal role for inducing suppression by OKT8 + cells.

We further evaluated the ability of cord blood T cells to express Ia-like antigens on stimulation with other mitogens or alloantigens, in comparison with their expression of Tac antigen which associated only with T cell activation. When stimulated with phytohemagglutinin, concanavalin A, PWM, or allogeneic cells, both cord blood and adult T cells expressed Tac antigen to a similar extent, which might be associated with cellular proliferation ability. In contrast, the expression of Ia-like antigens appeared to show some time lag behind the Tac expression of stimulated T cells. Of importance, it was found that the Ia expression of cord blood T cells on activation by these stimuli was markedly low as compared with adult ones. These observa- tions suggested that impaired ability to develop Ia-like antigens on stimulated T cells seemed to imply functional immaturity of T cells in early human ontogeny.

III. Clinical Problems in Reproductive Immunology

THE IMMUNOLOGY OF RECURRENT ABORTION.

Alan E. Beer, M.D., Department of Obstetrics and Gynecology, University of Michigan Medical School, Ann Arbor, Michigan, U.S.A, 48109.

In nearly all species studied, specific immunological or quasi-immunological systems that oper- ate to eliminate or inactivate non-self agents appear important for survival. The successful implan- tation, invasion, and survival of the genetically alien fetoplacental unit to term in the mammalian uterus has required specific modification or inactivation of the system(s). Early work claiming status of the placenta and its membranes as an immunologically privileged or null tissue based on the lack of MHC antigens on the syncytial trophoblast appeared a clean solution to the dilemma. However, recent evidence documenting MHC class 1 and class 2 antigen expression of the engraft- ing cytotrophoblast and the fetal membranes has focused intense interest on immunological pro- casses in the mother and the fetus that contribute to the status of the fetoplacental unit as extrin- sically determined privileged tissue. Careful observations over the past few years have documented that: 1) gestating females are aware of the presence and activities of allogeneic tissues within their reproductive tracts; 2) immune responses to these allogeneic tissues are initiated; and 3) responses aid in the establishment of the immunologically privileged status of the fetoplacental unit. Is lack of or aberrent immunoreactivity on the part of the female to fetoplacental antigens operating in couples experiencing recurrent abortions of unknown etiologies? It has been reported that a