Interleukin-2-dependent long-term cultures of low-density lymphocytes allow the proliferation of lymphokine-activated killer cells with natural killer, Tiγ/δ or TNK phenotype

We have developed a culture system for "longterm" growth of human lymphokine-activated killer (LAK) cells exhibiting an elevated, wide-spectrum antitumor cytotoxicity. The system allows the exponential growth of monocyte-depleted low-density lymphocytes in the presence of human serum and recombinant human interleukin-2 (10³ U/ml), alone or in combination with interleukin-1 α or β (both at 10 U/ml). Eighteen cultures were established from 18 normal adult donors. The membrane phenotypes of the final LAK cell population, assessed by a panel of monoclonal antibodies (mAb), consist of three main types: (a) NKH-1⁺, Tiα/β^-, Tiγ/δ^-, and CD3^- lymphocytes; (b) NKH-1⁺, Tiα/β^-, Tiγ/δ⁺, and CD3⁺ lymphocytes and (c) NKH-1⁺, Tiα/β⁺, Tiγ/δ^- and CD3⁺ lymphocytes. Northern blot analysis showed that all these cell populations express relatively high levels of perforin RNA, particularly cells exhibiting the first phenotype. This culture system may provide a tool for cellular and molecular studies on the mechanisms of antitumor cytotoxicity, as well as the basis for new adoptive immunotherapy protocols in advanced cancer.