Alteration in IL-1 and arginase activity of tumor-associated macrophages: A role in the promotion of tumor growth

The present investigations were undertaken to study whether the macrophages associated with Dalton's lymphoma (DLAM), a spontaneous T-cell lymphoma, are modulated for the secretion of tumor growth-promoting factors in ascites. The DL ascitic fluid (DLAF) and the culture supernatants of DLAM harvested from mid and late tumor-bearing stages, but not early tumor-bearing stage, enhanced the proliferation of DL cells in vitro. These observations indicate that DLAF contains certain DL growth-promoting substances and at least some of them are secreted by DLAM. The DLAM obtained from mid and late tumor-bearing stages showed enhanced IL-1 production and arginase activity, with a concomitant decline in the RNI production, which could be implicated in the DLAM-mediated promotion of tumor growth.