HIERARCHY OF SPEA PRESENTATION TO T-CELLS BY MOUSE MHC HAPLOTYPES

The ability of splenic antigen-presenting cells (APC) from nine indepe ndent mouse major histocompatibility complex (MKC) haplotypes to prese nt recombinant streptococcal exotoxin A (rSPEA) to heterogeneous T cel ls and mouse T cell clones were compared using proliferation assays. W e report that there is marked variation between MHC haplotypes, which can be ranked as follows: H2(z) > H2(s) = H2(f) = H2(p) = H2(r) = H2(k ) > H2(d) > H2(b) = H2(q). In some haplotypes both A and E molecules b ind rSPEA with low affinity. In addition, we show that presentation is preferentially by E molecules in haplotypes where A and E are co-expr essed, but that A alleles also bind and present rSPEA, based on inhibi tion of responses by anti-E and anti-A mAbs. Furthermore, using strain s of mice which fail to express E, we demonstrate that A(s) and A(f) p resent rSPEA with high efficiency, whereas A(q) and A(b) are the least efficient of all haplotypes. The results suggest that there is signif icant variation in the ability of different alleles of both E and A mo lecules to bind and present rSPEA.