LACK OF CORRELATION BETWEEN NATURAL-KILLER ACTIVITY AND TUMOR-GROWTH CONTROL IN NUDE-MICE WITH DIFFERENT IMMUNE DEFECTS

Abstract

To elucidate the in vivo role of natural killer (NK) cells, the growth of several murine and human tumors was studied in 4 variants of athymic, nude mice with different levels of NK activity. Beige-nude mice, homozygous for both the beige and the nude genes, had very low levels of NK activity, and their response to the B-cell mitogen, bacterial lipopolysaccharide, was lower than that of high-NK, adult NIH nude mice. Young and adult NIH nudes had different NK levels and showed different response in assays for K cell [Killer cell], T cell and B cell activity. The B cell-defective NIH-II mice had slightly lower NK levels than adult NIH animals, but much lower response in the antibody-dependent cell-mediated cytotoxicity assay. No correlation was found between host NK activity and the s.c. growth of various human (LOX, CEM, K562) and murine (YAC-1) tumor cells. Low NK activity was not associated with increased lung colony formation in a metastasis model using i.v.-injected human (LOX) and murine (B16F10) melanoma cells. No relationship was found between host NK activity and the rate of elimination of i.v.-injected 5-iodo-2''-deoxyuridine-labeled LOX, B16F10 and YAC-1 cells from lungs, liver or spleen. The results fail to support the view that NK cells exert significant direct effects on tumor cells in vivo.