Inflammation and anti‐tumor resistance. V. Production of a cytostatic factor following cooperation of elicited polymorphonuclear leukocytes and macrophages

Abstract

When Lewis tumor cells (3LL) included in a gel of polyacrylamide microbeads are injected into mice and recovered 1 day later, incorporation of 125I-UdR is strongly reduced. In contrast, no reduction is observed in irradiated mice. The cytostatic effect is non-existent in 6 hr-old granuloma (granulocytes 90%, macrophages 10%), but is maximal in 48 hr-old granuloma (granulocytes 50%, macrophages 50%). When 6 hr-old granuloma cells (which are not cytostatic) are incubated with bone-marrow-derived macrophages (BMs) (which are slightly cytostatic), considerable cytostasis against 3LL is observed, such an effect being strongly reduced if the 2 cell populations are separated. This suggests that close contact of live polymorphs with macrophages is necessary for full expression of cytostasis. No increase in cytostasis of bone-marrow macrophages is observed when BMs are incubated with a cell-free extract of freeze-thawed 6-hr-old granuloma cells. Cell contact is not necessary between granuloma cells and 3LL since the cytostatic activity is found in the supernatant of incubated phagocytic cells. Cytostasis is also observed with B16, P815, J774 cells and normal mouse bone-marrow cells. An active cytostatic fraction has been purified from the supernatant of 48-hr-old granuloma cells following molecular filtration and HPLC. The cytostatic factor has a low molecular weight (400-500 daltons), is not a peptide and presents maximum absorption at 267 nm.