Adherence of Salmonella typhimurium to murine peritoneal macrophages is mediated by Lipopolysaccharide and complement receptors

Adherence of Salmonella typhimurium to mouse peritoneal macrophages (M0) was monitored using a direct microscopic assay and flow cytometry. Competitive binding studies using wild type lipopolysaccharide and derivatives confirmed a role for this moiety in bacterial adherence. M0 pretreated with 2-deoxy-D-glucose exhibited lower binding activity than did untreated controls, suggesting involvement of either Fc or complement receptors. Preexposing M0 to Fc fragments, however, failed to reduce bacterial binding, thus eliminating a role for Fc receptors in this process. M0 pretreated with neutrophil elastase exhibited a diminished ability to bind S. typhimurium, suggesting involvement of complement receptor 1. Monoclonal antibodies M1/70 and M18/2, specific for epitopes on the α and β chains, respectively, of complement receptor 3, also blocked this adherence. In each case we were unable to eliminate completely bacterial adhesion to M0. Monoclonal antibodies to two additional M0 receptors, Mac-2 and Mac-3, did not block bacterial attachment. These data indicate that multiple mechanisms are involved in the initial adhesion of S. typhimurium to mouse M0.