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Production of interleukin 1 (IL-1) by leukemic cells was studied in 13 cases of acute myeloid leukemia. Intracytoplasmic immunofluorescence studies showed that the cells invariably contained the cytokine. Endogenous labeling studies demonstrated that acute myeloid leukemia cells produced either only the 33-kDa propeptide or both the propeptide and the 17-kDa mature form of IL-1 beta. The 33-kDa propeptide IL-1 alpha was always produced but was less frequently released. Involvement of IL-1 in leukemic cell growth was investigated using two antibodies specific for IL-1 subtypes, which inhibited spontaneous cell proliferation in the six cases studied. After acid treatment of the cells, a surface receptor for IL-1 could be demonstrated, which mediated 125I-labeled IL-1-specific uptake by leukemic cells. Furthermore, recombinant IL-1 alpha or IL-1 beta induced significant cell proliferation in 10 of 12 cases. The above findings were uncorrelated with the cytologic type (French-American-British classification) of leukemia. Our studies suggest that IL-1 may act as an autocrine growth factor in most cases of acute myeloid leukemia.
Cozzolino et al. (Sat,) studied this question.