Abstracts 93

3 of 30 low reactors made T cell antibodies while 8 of 14 in the presensitized group made T cell antibodies. It is interesting that these 3 positive T cell patients of the low reactors had previous exposure to HLA antigens by pregnancy, DST, and transplant. The remaining 3 positive low reactors had B warm antibodies which proved to be "true" B cell specific (non-class 1) antibodies by flow cytom- etry. Thus, imuran can successfully control the primary immune response in the "unsensitized" DST recipients but cannot suppress antibody formation in the patients with a history of presensitization and/or exposure to HLA antigens. Therefore, 27 of 27 "unsensitized" patients treated with imuran were eligible for transplantation.

ANTI-IDIOTYPIC IMMUNITY AND ITS RELEVANCE 1N TRANSPLANTATION. Elain Reed, Patricia Fazio-Miceli, Patricia Dowd, and Nicole Suciu-Foca; College of Physicians and Surgeons, Columbia University, New York. NY

We have postulated that idiotypic anti-HLA antibodies (Abl) induce the for- mation of anti-idiotypic (anti-Id) antibodies (Ab2), and that such anti-Id may secure allogeneic tolerance in pregnancy and transplantation. To test this hy- pothesis, sera from recipients of donor specific transfusions, and of kidney trans- plants, were tested for anti-Id activity. Briefly, our assay system resides in testing the capacity of the F(ab')2 obtained from a serum devoid of Abl to inhibit the reactivity of an Abl positive sample obtained from the same individual. The anti- Abl specificity of a blocking antibody (Ab2) is then determined by testing the capacity of the serum with the putative Ab2 to inhibit Abl of various specificities. Both lymphocytotoxicity and cytofluorometric determination of antibody binding are used in this system. Our investigations showed that while AB1 is detectable in only 10% of the recipients of donor-specific transfusions, Ab2 anti-anti-class I and anti-anti-class II is invariably present in all of them. Dissociation of Ab2 from Abl through dilution allows Abl to be revealed by cytofluorometric de- termination of antibody binding to target lymphoblasts. In renal allograft recip- ients the presence of Ab2 is associated with a state of quiescence. In ~'ne patient the disappearance of Ab2 activity from the serum was concomitant with the appearance of cytotoxic Abl (anti-HLA) and with the onset of rejection. This situation is reminiscent of that found in pregnancy where the titer of Ab2 prevails over Ab 1 during the first 7 months, with a reversion of this ratio in the proximity of delivery. The Ab 1-Ab2 interaction displays exquisite specificity since the Ab2 blocked only anti-HLA sera directed against the immunizing donor's antigens. Successful renal transplantation was accomplished in two patients who at the time of transplantation had no Abl activity against the donor, although they showed anti-donor HLA antibodies in sera obtained one year earlier. The cross-match- negative sera had high titers of Ab2. It therefore seems likely that the devel- opment of Ab2 to HLA antibodies provides a regulatory mechanism for sup- pressing the immune response to alloantigens and securing allograft tolerance.

DEFECTIVE AFFERENT IMMUNE FUNCTIONS IN LONG-TERM RENAL ALLOGRAFT RECIPIENTS. Thomas M. Ellis, T. Mohanakumar, and H. M. Lee; Medical College of Virginia, Richmond, VA

A significant role for afferent immune function in allograft rejection has recently received considerable experimental support. Studies were therefore performed to identify and characterize alterations in normal afferent immune functions that

94 Annual AACHT Meeting, 1984

are associated with long-term (>3 years) HLA-nonidentical renal allograft ac- ceptance. Twenty-one allograft recipients were evaluated for proliferative re- sponses in the autologous (AMLR) and allogeneic (allo-MLR) mixed lymphocyte responses as well as to a soluble antigen (tetanus toxoid). Mean recipient re- sponses in the AMLR (14,937 + 3243) and allo-MLR (87,789 -+ 8242) closely approximated those generated by normal controls (16,101 _+ 3005 and 86,082 _+ 7423, respectively). Despite vigorous proliferation in the AMLR, 7 of 8 recipients failed to generate allospecific CTL following AMLR stimulation in the presence of allogeneic E ~ cells. In addition, allograft recipients displayed sig- nificantly reduced proliferative responses to optimal concentration of tetanus toxoid when compared to normals (18,094 -+ 5545 vs. 48,935 -+ 8813; p < 0.001). Addition of up to 10 ( 'M indomethacin, purified IL-1 and/or IL-2 failed to reconstitute this response. Mixing experiments suggested that an inability of recipient accessory cells to appropriately present antigen might underlie the proliferative deficiency observed. These studies thus suggest that long-term renal allograft recipients possess characteristic alterations in T-helper and accessory cell functions that may provide an advantageous environment for the survival of HLA- mismatched allografts. (Supported by AM32209, AM32253, and CA27416.)

GENETIC FACTORS THAT INFLUENCE IMMUNE-RESPONSIVENESS TO NON-MHC TRANSPLANTATION ANTIGENS IN THE RAT. L. C. Paul, J. J. Blankert, and L. A. van Es; University Hospital Leiden, Leiden, The Netherlands

Immunization of MAXX(RTI") rats with pooled spleen and lymph node cells from the MHC-identical BN(RTI") strain results in the formation of alloanti- bodies to a non-MHC transplantation antigen on peritubular capillary and venous endothelium of the kidney from BN(RTln) , BUF(RTlb), WKA(RTlk), and WKY(RTlk). Since the ACI (RT1 ~) strain did not respond to this antigen pre- sented by BN cells, the in vivo humoral immune response was examined in 8(MAXXxACI)FI, 53(MAXXxACI)F2, and 13(MAXXxACI)FI x ACI animals. After repeated immunization the sera were tested in an indirect immunofluo- rescence test using kidneys from BN, BN.DA(RT1 ~') strains that carry the endo- thelial antigen and are MHC-identical to the responding strain. Since none of the RT1 ~ homozygous animals responded whereas 44/46 animals that were RT1 ~vn or RT1 n/n formed antibodies, the response is MHC linked. Using the RT1 re- combinant strains DA.BI(TR1.AnBaDaE ") and WRC(RT1.A"B°D~), the immune response gene was mapped within the class II loci of the MHC. Nei ther MHC incompatibility between donor and recipient nor the MHC on the immunizing cells influenced the response because MAXX rats responded to the endothelial antigen presented on BN. IL(RTll) , WKA(RTlk), or WKY(RT1 a) immunizing cells, whereas ACI rats failed to respond to the endothelial antigen on BN.DA (RT1 ~) cells. Using congenitally athymic rats on a responder WAG/Rij back- ground it was shown that the response to the endothelial antigen is T cell de- pendent. From this study we conclude that the immune response towards the non-MHC endothelial antigen is thymus dependent and encoded within the class II region of the MHC.

PREVENTION OF CYCLOSPORINE (CyA) INDUCED NEPHROTOXICITY IN RATS BY 16,16-DIMETHYL PROSTAGLANDIN E2 (dmPGE2). J. A. Falk, L. Makowka, T. Gilas, F. L. Moffatt, M. J. Phillips, and R. E. Falk; Toronto Western Hospital. Toronto, Ontario, Canada