Lipopolysaccharide-induced suppression of phagocytosis: effects on the phagocytic machinery.

We have shown previously that Lipopolysaccharide (LPS) can suppress macrophage phagocytosis and that suppression was not mediated by the induction of cytokines (1). In this study we investigated the mechanisms by which LPS may be suppressing phagocytosis in thioglycolate-elicited murine peritoneal macrophages, by evaluating the effect of LPS on various components of the phagocytic machinery. LPS mediated suppression in vitro was not due to reduced Fc gamma receptor gene expression. LPS-treatment did result in a slight reduction in the number of Fc gamma RI receptors but this reduction could not account for the degree of suppression seen following LPS treatment. LPS treatment altered the distribution of microfilaments and microtubules and Møs with such alterations had reduced phagocytic activity, suggesting that LPS may be suppressing phagocytosis via its effects on the cytoskeletal network. LPS administration in vivo also resulted in reduced phagocytic activity.