CYTOTOXIC-T-LYMPHOCYTE RESPONSES TO EPITOPES OF LISTERIOLYSIN-O AND P60 FOLLOWING INFECTION WITH LISTERIA-MONOCYTOGENES

In order to test the influence of the cell surface density of a specif ic H2-K-d-presented epitope on the subsequent level of the cytotoxic-T -lymphocyte (CTL) response directed against the epitope, we investigat ed the CTL response to two secreted products of Listeria monocytogenes from mice immunized with viable L. monocytogenes. We determined the r esponse to the H2-K-d-presented amino acid 91 to 99 (aa91-99) immunodo minant peptide of listeriolysin O (LLO) and to the aa217-225 immunodom inant peptide of p60. The p60-derived peptide appears at the cell surf ace as an H2-K-d-complexed peptide at a level sixfold higher than that of LLO aa91-99. CTL frequency analysis of anti-LLO- or anti-p60-speci fic CTLs from mice immunized with wild-type L. monocytogenes showed th at the numbers of immune spleen cell-derived CTLs specific for the two peptides were essentially equivalent. We have also found that Listeri a-specific CTL populations lyse target cells pulsed with the p60 aa217 -225 peptide with a magnitude of the lyric response markedly less than that for targets pulsed with the LLO aa91-99 peptide, Additionally, i mmunization with mutants oft. monocytogenes which do not stimulate ant i-LLO-specific CTLs does not alter the CTL frequency of anti-p60-speci fic effector cells, with levels of anti-p60-specific CTLs similar to t hose seen in mice immunized with wild-type L. monocytogenes. These res ults suggest that the relative cell surface density of major histocomp atibility complex class I-presented L. monocytogenes-derived epitopes Is but one of the criteria which determine the magnitude of the cytoto xic effector cell response that develops in antilisterial immunity.