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Antitumor Activity of Recombinant Human Interleukin‐1 against Heterotransplanted Human Non‐Hodgkin Lymphomas in Nude Mice

Antitumor activity of recombinant human interleukin 1α (IL‐1) against seven human non‐Hodgkin lymphomas grown in athymic nude mice was studied. Growth of the lymphomas was markedly inhibited after an injection of 0.4 mg/kg IL‐1. The growth inhibition of Burkitt lymphoma was found to be dose‐dependent up to 0.4 mg/kg, reaching a plateau thereafter. The loss of colony‐forming ability of the cells and the loss of cell viability showed the same type of dose‐dependence and progressed during 24 h following an injection of IL‐1. In accordance with these observations, histopathologic examination revealed progressively spreading coagulative necrosis without bleeding. Little infiltration of inflammatory cells into the tumor tissue was observed. IL‐1 growth inhibition of T lymphoma in beige nude mice having low natural killer activity was similar to that in nude mice. These findings suggested that the antitumor effects might not be produced through cell‐mediated antitumor actions. Immunocytological examination with anti‐IL‐1 antibody revealed that administered IL‐1 was bound to the lymphoma cells, suggesting that IL‐1 receptor is probably expressed on these cells in vivo. The antitumor action of IL‐1 on the lymphomas may be exerted directly through the IL‐1 receptor.