In vitro cytotoxicity to various human tumor cell lines of a tumor cytotoxic factor(s) produced by human alveolar macrophages.

When human alveolar macrophages (AM) obtained by lavage of the lungs of healthy donors were incubated in medium with or without lipopolysaccharide (LPS) they released a factor(s) with tumor cell killing activity. This tumor cytolytic and/or cytotoxic factor(s) (TCF) was assayed by measuring its effect in inhibiting target cell growth. TCF activity was not observed in the supernatant from cultures of LPS-treated hematopoietic malignant cell lines (monocytic leukemia, B-cell leukemia and T-cell leukemia cell lines). Human TCF was significantly cytotoxic to 13 of 15 solid-tumor cell lines tested and to 7 of 9 hematopoietic malignant cell lines, but not to two different normal, nontumorigenic cell lines. TCF-rich supernatants contained low levels of interferon (IFN) activity that were not significantly cytotoxic to A-375 melanoma cells. Human TCF and IFN-alpha or IFN-beta had additive cytotoxic effects. These data suggest that human TCF released by activated human AM may be of potential use in the treatment of malignant disseminated diseases.