Increased sensitivity of IL2-dependent cultured T cells and enhancement of in vitro IL2 production by human lymphocytes treated with bestatin

Bestatin is an inhibitor of leucine aminopeptidase and aminopeptidase B which potentiates various immune functions, such as delayed hypersensitivity and antibody formation, and inhibits tumor cell growth in animal models. Our study focuses on the effect of Bestatin on interleukin 2 (IL2) sensitivity of IL2-dependent cultured T cells (CTC) and on IL2 production by human peripheral blood mononuclear cells (PBM). Bestatin (0.01 – 10 μg/ml) increases CTC 3H-TdR incorporation in the presence of suboptimal (low) concentrations of exogenous IL2. Bestatin alone has no mitogenic effect on CTC. This phenomenon is due to increased CTC IL2-receptors after treatment with Bestatin. Bestatin (1 – 10 μg/ml) also increases (1.4 – 21 fold) IL2 production by PHA-stimulated PBM. Bestatin therefore increases both IL2 sensitivity and IL2 production. This may explain the various immunopotentiating effects of Bestatin previously described.