ALLOANTIGEN-INDUCED HUMAN-LYMPHOCYTES RENDERED NONRESPONSIVE BY A COMBINATION OF ANTI-CD80 MONOCLONAL-ANTIBODIES AND CYCLOSPORINE-A SUPPRESS MIXED LYMPHOCYTE-REACTION IN-VITRO

Induction of a state of long-term, alloantigen-specific T cell nonresp onsiveness has significant implications for human transplantation, It has been previously described that alloantigen-specific anergy may be induced by addition of cyclosporin-A together with anti-CD80(B7-1) mAb to a MLR, In this study we endeavored to verify whether alloantigen-i nduced PBL rendered anergic by the addition of a combination of anti-B 7 mAb and cyclosporin-A during a MLR had a suppressive effect when add ed to autologous lymphocytes activated in MLR, We found that: 1) the a ddition of cells rendered anergic by this procedure to a MLR suppress both proliferative and cytotoxic response of autologous responsive PBL to either the same or third-party stimulator cells; 2) the suppressiv e effect is limited to alloantigen-induced T cell activation, as addit ion of anergic cells does not influence mitogen- or antigen-induced pr oliferation of autologous responsive T cells; 3) nonresponsiveness of suppressed cells cannot be reversed by either subsequent restimulation with allogeneic cells or addition of exogenous IL-2 to the cultures; 4) the suppressive effect is apparently npt due to secretion of anergi c cell-derived soluble factors, but it seems to be dependent on cell-c ell contact between anergic, responsive, and stimulator cells, These d ata suggest that: 1) the delivery of a direct signal mediated by anerg ic lymphocytes through a cell-cell contact is likely to be the mechani sm responsible for the suppressive effect here described; 2) anergic c ells may propagate alloantigen-specific tolerance to potentially respo nsive autologous lymphocytes. Preliminary experiments indicate that an ti-CD86(B7-2) mAb may play a similar role in the generation of alloant igen-induced nonresponsiveness.