Homologous Human Macrophage Hybridomas That Produce a Novel Cytotoxic Factor in Their Culture Supernatants

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Abstract
Homologous human macrophage hybridoma cell lines were obtained by somatic cell fusion between peripheral blood monocyte‐derived macrophages and a subclone of the myelomonocytic cell line, U937‐F9. The hybridoma cell lines grown in vitro for more than a year were confirmed by manifestations of phagocytosis, adherence, nonspecific esterase, acid phosphatase, chromosome numbers and other cell surface antigens. Cell surface antigens on hybridomas were detected by flow cytometry analysis with monoclonal antibodies. With interclonal differences, a typical phenotype of hybridoma cells was CDw14+, OKM5+, Mac‐1+ (equivalent to OKM1 and Mol), OKT9+, HLA‐DR− and CD20+. After stimulation with lipopolysaccharide and calcium ionophore A23187, culture supernatants of clones c18A and c29A showed cytotoxic activity against human melanoma A375 Met‐Mix and other cell lines which were resistant to the tumor necrosis factor, lymphotoxin and interleukin 1. This cytotoxic factor was found to be distinct from the tumor necrosis factor, lymphotoxin and interleukin 1 using the anti‐tumor necrosis factor, anti‐lymphotoxin and anti‐interleukin 1 antisera.