Cell activation and death (apoptosis) induced by IL-2: ultrastructural evidence.

Peripheral blood cells of cancer patients with advanced renal carcinoma and treated with interleukin-2 by intravenous application were studied by electron microscopy at different intervals from the beginning of rIL-2 administration. Morphofunctional modifications of lymphocytes, circulating hystiocytes containing phagocitated bodies and polimorphonucleated cells undergoing phagocytosis were observed with a time dependent increase of altered cells. The analysis of blood cells cultured in the presence of recombinant IL-2 confirmed the in vivo results. Our data suggest that IL-2 induces apoptotic phenomena in the peripheral blood cells of treated patients.