Analysis ofthehumanT cell responsiveness topurified antigens ofLeishmania: lipophosphoglycan

SUMMARY Theresponsiveness ofperipheral bloodlymphocytes from15cutaneousleishmaniasis patients and five healthy volunteers topurified surface antigens ofLeishmania was studied. Thefollowing purified antigens wereindependently used asstimuli forlymphocyte proliferation invitro: lipophosphoglycan ofL.braziliensis, (Lb-LPG), lipophosphoglycan ofL.mexicana(Lm-LPG), glycoprotein 63of L.braziliensis (Lb-gp 63)andglycoprotein 63ofL.mexicana (Lm-gp63). Amongsixpatients tested withLb-gp63andLm-gp63,twoborderline responsesandtwopositive responses were observed, respectively, alltheothers being negative. Lb-LPGandLm-LPGinduced positive responses inall patients tested (11withLb-LPGandfive withLm-LPG).A positive dose-response correlation was observed intheresponsesofthepatients tobothLb-LPGandLm-LPG.Significant differences (P<0-01) were foundbetween thetwo groups (patients andhealthy subjects) withregard tothe responsestoLb-LPG. Theproliferating cells after stimulation withLb-LPGwere showntobelong to theCD4+Tcell subset byflowcytometry. However, thefollowing evidence suggests thattheTcell responseswere notinduced byLPG itself butrather byprotein contaminants intheLPG preparations: a highly purified Lb-LPGbatch thathadundergone additional purification induced positive responsesincells fromonlythree outofsixpatients anda proteinase K-treated Lb-LPG batchdidnotstimulate any positive responseamong thesame sixpatients.