Interleukin-2 and the regulation of activated macrophage cytotoxic activities.

Abstract

In 1976, Morgan and colleagues reported that conditioned media from mitogen-stimulated mononuclear cells contained a factor which maintained the exponential proliferative growth of human leukemic blood or bone marrow cells (1); the proliferative cells were identified as normal T lymphocytes (2). Isolation, characterization, and subsequent purification of this factor in the conditioned medium lead to the identification of a T cell growth factor (TCGF) now known as IL-2 (3), a glycoprotein of 15.5 kD with a slightly basic isoelectric point (4). Shortly thereafter, Taniguchi et al. (5) isolated a cDNA clone for IL-2. Although IL-2 was initially described as the ultimate mitogenic signal for both antigenically and polyclonally activated T cells, aiding in their cell cycle transition from G1 to S phase (6), subsequent studies showed that IL-2 stimulates NK and LAK cell activity (7, 8), induces B cell differentiation and proliferation (9), and activates macrophage cytotoxicity (10). IL-2 also participates in induction of T cell synthesis of cytokines, such as IFN-γ (11) and B cell growth factor-1, or IL-4 (12).