PRESENTATION VIA THE CLASS-I PATHWAY BY LEISHMANIA-AMAZONENSIS-INFECTED MACROPHAGES OF AN ENDOGENOUS LEISHMANIAL ANTIGEN TO CD8(-CELLS() T)

CD8(+) T cells play a protective role in immunity to cutaneous leishma niasis, However, it has been unclear how these cells execute this func tion, since results from several investigations attempting to demonstr ate recognition of Leishmania-infected macrophages by CD8(+) T cells h ave been contradictory, In this study, we report the generation of CD8 (+) T cell lines specific for GP46/M-2, a leishmanial Ag, previously s hown to protectively immunize mice against a Leishmania amazonensis ch allenge. Using T cell cytolysis and IFN-gamma production to assess CD8 (+) T cell activation, we show that in addition to recognizing mammali an cells transfected with GP46/M-2, these CD8(+) T cell lines also rec ognize macrophages infected with Leishmania amazonensis, MHC class I p resentation of GP46/M-2 by infected macrophages can be blocked by trea tment with brefeldin A and also by inhibitors of the cytosolic multica talytic proteasome, N-acetyl-L-leucinyl-L-leucinal-L-norleucinal and N -acetyl-L-leucinyl-L-leucinylmethional. These results suggest that thi s leishmanial Ag is processed in the macrophage cytoplasm and is prese nted to CD8(+) T cells via the classical pathway of MHC class I presen tation. The relevance of these findings as they impact on our understa nding of the biology of the parasite within the macrophage is discusse d.