Lysis of murine macrophages infected with intracellular pathogens by interleukin 2-activated killer (LAK) cells in vitro

To determine if murine lymphocytes activated by interleukin 2 (IL-2) were cytotoxic against syngeneic elicited peritoneal macrophages (Mφ) infected with intracellular pathogens, splenocytes that had been cultured with IL-2 for 5 or 10 days were studied in vitro. These cells, [lymphokine-activated killer (LAK) cells] showed significantly greater cytotoxicity against Mφ infected with Leishmania major or Legionella pneumophila than against uninfected Mφ. Preferential cytotoxicity against infected Mφ was best shown using effector-to-target-cell ratios of 1:1-20:1; when ratios ≥40:1 were employed, uninfected Mφ were also lysed. The extent to which Mφ that had been incubated with L. major were lysed depended upon the proportion of Mφ containing intracellular organisms. After infection with L. major, the duration of incubation did not appear to influence the degree of lysis by LAK cells.