RECOGNITION OF MEASLES VIRUS-INFECTED CELLS BY CD8(-CELLS DEPENDS ON THE H-2 MOLECULE() T)

H-2d mice are resistant to measles virus-induced encephalitis (MVE) an d develop L-d-restricted CD8(+) T cells which lyse target cells infect ed with measles virus or with a vaccinia virus recombinant expressing the nucleocapsid protein of measles virus (vvN). In contrast, H-2k mic e are susceptible to MVE and generate CD8+ T cells which lyse target c ells infected with vvN, but not those infected with MV. We were able t o demonstrate that this difference is not due to a defect in the antig en processing machinery, but that K-k molecules require 100-fold more peptide to sensitize target cells for lysis by CTL. vvN replicates wel l in target cells and therefore enhances the level of epitope peptide available for CTL recognition. In contrast, MV infection is abortive i n mouse cells and low levels of epitope peptide are produced. As Ld re quires 100-fold less peptide than K-k to sensitize target cells for ly sis, the low level of epitope peptide is enough to induce lysis by CD8 + T cells, whereas for recognition via K-k, increased synthesis of pro tein is required. We propose that the differences in peptide binding b etween the two H-2 molecules will have consequences for the kinetics o f the generation of CD8+ T cells as well as the absolute numbers of CD 8+ T cells generated.