AN H2-T MHC CLASS LB MOLECULE PRESENTS LISTERIA MONOCYTOGENES-DERIVEDANTIGEN TO IMMUNE CD8(-CELLS() CYTOTOXIC T)

Mouse spleen T cells can adoptively transfer immunity to Listeria mono cytogenes; this activity was markedly enhanced by stimulation with Con A in vitro before transfer. The enhanced and prolonged protection aga inst L. monocytogenes in vivo was correlated with enhanced lysis in vi tro of target cells infected with strains of L. monocytogenes that pro duce listeriolysin O (LLO). One of the targets of such cytotoxic cells from BALB/c (H2(d)) mice was a peptide that corresponded to amino aci ds 91 to 99 (p91-99) of the LLO molecule, which satisfies the binding motif of H2-K-d. Listeria-immune CD3(+)CD8(+), but not CD3(+)CD8(-), c ells could also lyse H-2-incompatible, infected target cells. Immune c ells from C57BL/6 (H2(b)) mice lysed allogeneic H-2(d) target cells in fected with L. monocytogenes or a Bacillus subtilis transformant that secretes LLO, but did not lyse targets pulsed with p91-99. This H2-unr estricted cytolysis was therefore directed at a fragment of the LLO mo lecule other than p91-99. Listeria-infected bone marrow macrophages fr om congenic and recombinant strains of mice were lysed only when they shared the H2-T region or were Qa1-compatible with the immune cytotoxi c cells; sharing of the H2-D, Q, or M region was insufficient. Thus, t he immune response to L. monocytogenes included cytolytic CD8(+) cells that recognized endogenously processed Listeria-derived Ags in the co ntext of the class la H2-K molecule, as well as a class Ib H2-T molecu le.