ANTIGEN-REACTIVE GAMMA-DELTA-T-CELLS IN HUMAN LEISHMANIASIS

The importance of Ag-specific gammadelta T lymphocytes in human immune response to pathogenic organisms is unknown. In the present study the expression of gammadelta TCR on T lymphocytes from patients with cuta neous, mucosal, or visceral leishmaniasis was examined. All of these p atient groups had elevated levels of gammadelta T cells in peripheral blood. Patients' gammadelta T cells included CD8+ as well as null cell s. The percentage of T cells expressing gammadelta TCR was increased s ignificantly by stimulation in vitro with certain parasite Ag. T-cell lines generated by stimulation with promastigote lysates of Leishmania amazonensis or L. braziliensis typically contained 25 to 60% gammadel ta T cells. In contrast, two immunodominant surface Ag of L. amazonens is, gp63 and gp42, did not expand gammadelta T cells from infected pat ients, although both Ag elicited strong alphabeta T-cell responses. ga mmadelta T cells isolated from a Leishmania-specific T-cell line respo nded to stimulation with promastigote lysate. Of particular interest, gammadelta T cells from PBMC of a patient with mucosal leishmaniasis r esponded to stimulation with a recombinant 70 kDa heat shock protein o f L. chagasi. This study demonstrated that several clinical forms of l eishmaniasis induced elevated numbers of gammadelta T cells that respo nded specifically to Leishmania Ag in vitro. Therefore, this component of the T-cell response to Leishmania