Adherence of Salmonella typhimurium to murine peritoneal macrophages is mediated by lipopolysaccharide and complement...

Adherence of Salmonella typhimurium to mouse peritoneal macrophages (Mø) 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. Mø pretreated with 2-deoxy-D-glucose exhibited lower binding activity than did untreated controls, suggesting involvement of either Fc or complement receptors. Pre-exposing Mø to Fc fragments, however, failed to reduce bacterial binding, thus eliminating a role for Fc receptors in this process. Mø 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 alpha and beta chains, respectively, of complement receptor 3, also blocked this adherence. In each case we were unable to eliminate completely bacterial adhesion to Mø. Monoclonal antibodies to two additional Mø 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 Mø.