Induction of antiidiotypic antibodies by donor-specific blood transfusions. Establishment of a human-mouse hybridoma secreting the MLR-inhibiting factor

Impact of transfusions and acute rejection on posttransplantation donor antigen-specific responses in two study populations. Cooperative Clinical Trial in Transplantation Research Group

BACKGROUND

We participated in a protocol supported by the National Institutes of Allergy and Infectious Disease, Cooperative Clinical Trial in Transplantation (CCTT), which was designed to investigate the effect of peritransplant donor-specific transfusion in non-HLA-identical living donor kidney recipients.

METHODS

We determined the donor antigen-specific responses at 1 year after transplantation for the 79 CCTT donor-recipient combinations in this study. A lower rate of donor antigen-specific hyporeactivity was seen in the CCTT recipients (6 of 79=8%) versus our recipients at the University of Minnesota who underwent transplantation in the same period (9 of 55=16%, P=0.16) and versus our combined historical data (33 of 131=25%, P=0.002). Therefore, we studied the differences in the two recipient populations to determine why hyporeactivity was lower in the CCTT group than at our center.

RESULTS

Significant differences were seen in the acute rejection rates and the frequency of pretransplantation random transfusion. Overall and early (<3 month) acute rejection rates were higher in CCTT versus Minnesota recipients (overall: 51% vs. 20%, P=0.001) (early: 43% vs. 16%, P=0.001). The frequency of pretransplantation random transfusion was 40% for CCTT recipients (34%) versus 80% for Minnesota recipients (75%) (P=0.0004).

CONCLUSIONS

These results provide provocative, although not conclusive, evidence for the importance of pretransplantation transfusion and acute rejection episodes in the development of donor antigen-specific hyporeactivity. Pre-, peri-, and posttransplantation clinical events undoubtedly have an impact on posttransplantation immune parameters.

Donor-specific transfusion and donor bone marrow infusion in renal transplantation tolerance: a review of efficacy and mechanisms

The ultimate goal in transplantation is modulation of the immune response to produce tolerance without immunosuppression. To date only a state of pseudotolerance for the allograft has been achieved through the use of potent pharmacologic and biologic manipulations. Despite these manipulations to prevent acute rejection, chronic rejection eventually results in graft failure. Thus, different strategies have been sought to induce tolerance and prevent acute and chronic rejection. Historically, donor-specific transfusion (DST) was one such strategy attempted. Donor-specific transfusion has been used primarily in living donor organ transplantation. With the concern that DST may sensitize patients, thereby preventing transplantation and introduction of cyclosporine, the use of DST was curtailed. More recently, donor bone marrow (DBM) infusion at the time of cadaveric transplantation has been used to facilitate development of microchimerism and tolerance to abrogate acute and chronic rejection. However, DBM infusion may predispose the recipient to graft-versus-host disease and is not easily accomplished in living donor organ transplantation. The potentially immunomodulating and tolerizing mechanisms of DST and DBM infusion are similar and include induction of anergy, stimulation of anti-anti-HLA antibodies, provision of soluble HLA antigen, suppressor cell and/or veto cell activity, clonal deletion, regulation of cell surface molecules, regulation of cytokines, promotion of microchimerism, or a combination of these. Of these mechanisms, microchimerism with the concomitant persistence of soluble donor HLA antigen is felt by many to be the most important. Although microchimerism is detectable in many patients who are tolerant of their grafts, there is no clear evidence that chimerism is responsible for the induction or maintenance of tolerance.

Analysis of suppressor T cells induced by donor-specific transfusion (DST): establishment of a human T cell hybridoma producing an antigen-nonspecific suppressor factor

Formation of suppressor T cells (Ts) induced by donor-specific transfusion (DST) is one of the most commonly suggested mechanisms for the beneficial effect of DST. In this study, we established a human T cell hybridoma derived from the peripheral blood lymphocytes (PBL) of a DST-treated patient, which produced an antigen-nonspecific suppressor factor. Post-DST PBL were fused with an azaguanine-resistant mutant of a human T cell leukemia cell line, CCRF-CEM(AG). After selection and cloning, we established one clone producing the mixed lymphocyte reaction (MLR) inhibitory factor (C524: 18%-43% suppression). Suppressive activity of the supernatant obtained from C524 after activation by PHA was highly augmented (64%-88% MLR suppression). This factor inhibited MLR dose-dependently in an antigen-nonspecific and HLA non-restricted manner. These results indicated that Ts clones could be generated in patients receiving DST and that the immunoregulatory factors produced by activated clones may play a role in the prolongation of renal allograft survival.

IgM anti-idiotypes that block anti-HLA antibodies: naturally occurring or immune antibodies?

Using dithiothreitol (DTT) technique, IgM anti-HLA anti-idiotypic antibodies were detected in a multiparous multitransfused woman. These antibodies were able to inhibit the binding of specific IgG anti-HLA antibodies on their corresponding antigen. The recognized determinants were cross-reactive determinants since they were partially found on anti-HLA antibodies from unrelated individuals. By studying the patient's sera over a period of 2 years, no IgM-IgG switch was observed but the presence of these antibodies was stable in time, despite the disappearance of the idiotypes (anti-HLA antibodies). However, when looking at the patient's earlier serum, it was shown that these IgM anti-idiotypic antibodies were absent from the first available serum. Thus, these anti-idiotypic antibodies seem to behave both like natural and immune antibodies. The incidence of such antibodies in pretransplant patients is discussed.