Antitumor and phagocytic activities of rat alveolar macrophage subpopulations separated on a discontinuous gradient of bovine serum albumin.

Alveolar macrophages (AM) lavaged from the lungs of normal F344 rats were separated on a discontinuous density gradient of bovine serum albumin (BSA) into four fractions designated as fraction A (20/25% BSA interface), fraction B (25/30%), fraction C (30/35%); and fraction D (35%/pellet). The abilities of these four fractions to form rosettes with opsonized sheep red blood cells (SRBC), to phagocytize these SRBC, and to become tumoricidal in response to macrophage-activating agents in vitro were examined. Fractions A and D had greater abilities than fractions B and C to form rosettes and to phagocytize opsonized SRBC, and a good correlation was found between these two activities in the four fractions. In contrast, the four AM fractions were equally susceptible to activation stimuli, such as lipopolysaccharide (LPS), Nocardia rubra cell wall skeleton (N-CWS), macrophage activating factor (MAF), muramyl dipeptide (MDP), or a mixture of MAF and MDP in vitro to become cytotoxic to syngeneic mammary adenocarcinoma cells.