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Induction by specific T lymphocytes of intracellular destruction of Leishmania major in infected murine macrophages

Summary The following cell populations derived from lymph nodes of mice primed in vivo with living Leishmania major promastigotes were tested for their capacity to induce parasiticidal activity in L. major‐infected macrophages: a L. major‐primed lymph node cells, draining lymph node cells from mice primed by a subcutaneous injection of living L. major in Freund's Complete Adjuvant; b L. major‐specific T blasts, i.e. blast T cells resulting from in vitro challenge of primed lymph node cells with L. major, c propagated L. major specific T blasts, i.e. blast T cells after propagation in vitro in antigen‐free medium containing interleukin‐2. Results indicate that cocultivation of these L. major specific lymphocyte populations with infected peritoneal exudate macrophages induced progressive destruction of intracellular L. major. This effect was antigen specific since similar populations obtained from mice primed either with ovalbumin or bovine serum albumin did not induce significant parasite killing. The various lymphocyte populations examined did not express cytolytic activity for syngeneic macrophages infected with L. major when tested in a short‐term 51Cr release assay. These negative results could not be attributed to an inability of infected macrophages to be lysed by cytolytic lymphocytes since cytolytic T lymphocytes directed to H‐2 alloantigens present on macrophages were perfectly capable of lysing these infected macrophages as revealed in a 4 h 5lCr release assay. Interestingly, infected macrophages from either BALB/c (H‐2d), NZB (H‐2d) or CBA (H‐2k) mice were lysed by cytolytic T lymphocytes specific for their respective H‐2 alloantigens as well as uninfected macrophages. These results suggest that H‐2 expression on the surface of infected macrophages from either L. major susceptible or resistant mouse strains is sufficient to be detected by allogeneic cytoloytic T lymphocytes.