HEAT-SHOCK COGNATE PROTEIN 71-ASSOCIATED PEPTIDES FUNCTION AS AN EPITOPE FOR TOXOPLASMA GONDII-SPECIFIC CD4(+) CTL

HLA-DR-restricted CD4(+) cytotoxic T-lymphocyte (CTL) lines specific f or Toxoplasma gondii (T. gondii)-infected melanoma cells have been est ablished from peripheral blood lymphocytes (PBLs) of a patient with ch ronic toxoplasmosis, The role of heat shock cognate protein (HSC) 71 i n antigen (Ag) processing and presentation of T. gondii-infected melan oma cells to these CD4(+) CTL lines was investigated, A human melanoma cell line (P36) pulsed with T.gondii-infected P36 cell-derived HSC71 was lysed by a T.gondii-specific CD4(+) CTL line (Tx-HSC-1), The Tx-HS C-1 also killed T.gondii-infected P36 cells, The lytic activity of Tx- HSC-1 against P36 cells pulsed with T. gondii-infected P36 cell-derive d HSC71 was inhibited by monoclonal antibodies (mAbs) against HSC71, A nti-human leukocyte antigen (HLA)-DR mAb also partially blocked the ly tic activity, whereas anti-HLA-A,B,C mAb did not block the lytic activ ity. In addition, a flow cytometric analysis with these specific mAbs against HSC71 showed HSC71 to be expressed on the cell surface of T. g ondii-infected P36 cells as well as uninfected P36 cells, These data i ndicate that HSC71 molecules are expressed on human melanoma cell line P36, and that HSC71 may play a potential role in Ag presentation and processing of T. gondii-infected P36 cells to CD4(+) CTL.