In vitro effects of lipopolysaccharides and mycobacterial cell wall components on swine alveolar macrophages

The possible activation of swine alveolar macrophages (AM) by lipopolysaccharides (LPS) and mycobacterial cell wall components such as muramyl dipeptide (MDP) and interphase material (IPM) was investigated. Swine AM were harvested by post mortem lung washings and the following functions were assayed: adherence and spreading in cultures; phagocytosis of (51)Cr-labelled chicken red cells; cytostatic activity against xenogeneic tumour cells (P815 mastocytoma cells); monokine synthesis; interferon and LAF (lymphocyte activating factor or inter-Ieukin-1). Incubation of swine AM with either MDP, LPS or IPM (0·1 μg to 100 μg/ml) for 24 hours did not affect the cell viability but increased their adherence and spreading slightly. Phagocytosis was not markedly modified. Under the same experimental conditions, the unstimulated AM cultures exhibited a strong cytostatic activity which was not modified by these components. No interferon synthesis could be observed in the normal or stimulated AM cultures. In contrast, LAF activity was consistently increased after 48 hours of incubation with LPS, whereas MDP produced this effect only in some experiments.