Influence of adoptively transferred thioglycollate-elicited peritoneal macrophages on metastasis formation in mice with depressed or stimulated NK activity.

The effect of thioglycollate-elicited macrophages (TG-M phi) on natural killer (NK)-cell activity and metastases formation in mice was investigated. Intravenously (i.v.) inoculated TG-M phi inhibited spleen NK activity of normal mice and abrogated polyinosinic: polycytidylic (poly I:C) induced augmentation of NK cell function. TG-M phi also inhibited the clearance of i.v.-injected radiolabeled B16 melanoma cells from the lungs of normal or poly I:C stimulated mice. Formation of experimental B16 melanoma metastases was dramatically increased in mice pretreated with TG-M phi. Administration of TG-M phi increased metastasis formation to a greater extent than anti-asialo GM1 serum, while anti-asGM1 serum was more efficient than TG-M phi in depressing spleen NK cell activity. When mice with low NK reactivity (beige mice or mice treated with anti-asialo GM1 serum) were inoculated with TG-M phi, there was a substantial additive augmenting effect on metastasis formation in the lungs. Treatment with poly I:C elevated NK-cell activity and had profound antimetastatic effects in normal but not in TG-M phi pretreated mice. The metastasis augmenting effect of TG-M phi was fully expressed in poly I:C-treated mice as well as in athymic nude mice. Inoculation of proteose peptone-elicited macrophages (PM phi), unlike TG-M phi, did not depress NK activity or augment metastasis formation in normal or poly I:C-treated mice. However, since the inhibition of NK activity in TG-M phi-treated mice was relatively weak, and a substantial additional increase in metastases was observed in NK-depressed mice after transfusion of TG-M phi, it seems unlikely that the TG-M phi-induced inhibition of NK reactivity is entirely responsible for the augmented formation of metastases. Further studies revealed that i.v. inoculation of TG-M phi, but not PM phi, induced intravascular inflammatory reactions, and damage to endothelial cells and basement membrane of the lung vasculature. These reactions may contribute to increased tumor cell extravasation and metastasis formation in mice pretreated with TG-M phi.