Abstracts 121

there was a significant difference (p < 0.05) for the group with four shared HLA B and DR antigen (n = 8) compared to the group with only one shared HLA- B or -DR antigen (n = 8) in the 1- and 2-yr graft survival rate (100%/100% compared to 62%/25%). The corresponding figures for 3 (2) shared B and DR antigens (n = 39/69), were 82% (84%) after 1 yr, and 82% (71%) after 2 yr. We conclude, therefore, that HLA-B and -DR antigen matching is strongly ben- eficial even in Cy-A treated patients.

INHIBITION OF HUMAN LYMPHOCYTE PROLIFERATION BY UV-B IRRADIATED CELLS AND SOLUBLE SUPPRESSOR FACTORS. B. Duffy, L. Sherman, and G. Rodey; American Red Cross Blood Sem~ices, Dept. of Pathology, Washington University School of Medicine, St. Louis, MO

Ultraviolet light irradiation (UV-B) abrogates stimulatory and responder prop- erties in mixed leukocyte reponse (MLR) and is believed to enhance rat pancreatic islet allografts by UV-B whole blood transfusions. We studied the effects of UV- B on 3-party MLR, mitogen proliferative responses and soluble suppressor factor production. Cultures consisted of a fresh MLR to which UV-B or gamma irra- diated (R) responder or stimulator peripheral blood mononuclear ceils (pbm) were added at time of culture. In both systems, allogeneic proliferation was reduced approximately 50% over control cultures. PHA-P, CON-A, and poke- weed mitogen (PWM) responses were also suppressed approximately 50, 20, and 30%, respectively. Thus treated cells have antigen nonspecific inhibitory activity. MLRs were performed with addition of UV-B or gamma R autologous pbm, purified T cells, or nonadherent cells to determine the nature of the cell inhibitor. In all experiments, T UV-B inhibition was comparable to pbm UV-B inhibition, while non-T UV-B inhibition was comparable to pbm UV-B in only 50% of studies. Suppression of CON-A and PHA-P responses by T cells were comparable to suppression induced by non-T cells. Supernatants from 6 day MLR containing UV-B or gamma R cells were harvested, filtered, and used 50% (vol/vol) in fresh media as a media supplement in a fresh MLR containing the original responder and stimulator cells. Supernatants derived from MLR containing UV-B R cells of responder origin consistently inhibited (50%) fresh MLR compared to su- pernatants of non-UV-B R cells. If a responder other than the original was substituted in the fresh MLR, only 25% inhibition was observed suggesting some degree of specificity. We confirm (Lederman et al.) suppression of mitogen in- duced proliferation by UV-B R cells and also show comparable inhibition of MLR reactivity and evidence of soluble inhibiting factors. Similar suppression, of UV-B R blood products, if possible, could be valuable in the pretransplant conditioning of recipients of allografts, while lowering allosensitization.

ENUMERATION OF HUMAN ALLOANT1GEN-REACTIVE HELPER T CELLS BY LIMITING DILUTION ANALYSIS. P. Adams, R. Ferguson, and C. Orosz; Therapeutic Immunology Labora- tories, The Ohio State University, Columbus, OH

We have developed a rapid, sensitive, and quantitative limiting dilution analysis technique that provides a minimal estimate of the number of human peripheral blood mononuclear cells (PBMC) capable of secreting Interleukin-2 (operation- ally defined as helper T lymphocytes) when cultured in vitro with allogeneic PBMC bearing serologically identified MHC disparities. We are currently aware of no other immunologic techniques which can quantitate human alloantigen- specific helper T lymphocytes (HTL). For this analysis, limiting numbers of human