Public B cell alloantigen determinants (Ia) and active enhancement of renal allografts in the rat.

Experimental renal transplantation in the rat model has established that immunity to certain donor B cell Ia antigenic determinants is associated with enhanced graft survival. Preimmunization of LEW hosts with BUF lymphoid cells produced significant prolongation (P < 0.005 by log rank analysis) of survival of renal allografts taken from a third-party (LEW X BN)F1. Serological analysis demonstrated that BN and BUF share and MHC-encoded public Ia specificity, expressed on B cells, which we have called Ia.15. Hyperimmune sera directed at this specificity are cytotoxic to 20 +/- 3% of lymph node cells, significantly inhibit the formation of EA rosettes by Fc receptor-bearing cells (EAI), and inhibit mixed lymphocyte reaction (MLR) by 50 to 60% when directed at the stimulator but not when directed at the responder strain cells. Study of a large number of hyperimmune sera raised between inbred rat strains, by EAI and complement-dependent cytotoxicity (CDC) versus B cells, has revealed broad patterns of cross-reactivity, suggesting that public Ia determinants are both complex and highly immunogenic. Immunity restricted to a public Ia antigen plays a role in allograft enhancement.