Tumour cell inhibition of macrophage cytokine activity

Abstract

Macrophages elaborate both effector and regulatory immune functions. It was hypothesised that tumours can exert a local alteration of macrophage function. Murine peritoneal macrophage‐derived cytokines were assayed in the presence and absence of cells, cytosol fractions or conditioned media (TCCM) from established murine tumour lines. Interleukin‐1β, interleukin‐6 and tumour necrosis factor‐α activities were significantly inhibited by tumour cells or their products, as were the corresponding recombinant human cytokines. Intracellular protein kinase C activation was also measured and was significantly inhibited by murine TCCM, thus suggesting one possible site of inhibitor action. Data analyses indicate that the inhibitory factor(s) is probably not an already well‐characterised macrophage inhibitor.

Activation of Tumor-Associated Macrophages by Thymosin Alpha-1

“…Macrophages represent the major component of the lymphoreticular infiltrate of tumors designated as tumor-associated macrophages (TAM) (2,6). TAM have been shown to not only contribute to tumor inhibition by exerting cytotoxic and cytostatic effects on tumor cells but have also the dubious distinction offacilitating tumor progression (2,4,(7)(8).…”