Pasteurella haemolytica A1 purified capsular polysaccharide does not stimulate interleukin-1 and tumor necrosis factor release by bovine monocytes and alveolar macrophages.

Purified capsular polysaccharide (CPS) stimulated significant release of interleukin-1 (IL-1) activity from bovine blood monocytes but not alveolar macrophages in vitro. The ability of CPS to induce IL-1 release was resistant to boiling and inhibited by the addition of polymyxin beta. Thus, it is likely that the IL-1 release stimulated by CPS resulted from the small amount of contaminating lipopolysaccharide (LPS) that was present (an estimated 5 pg LPS per microgram CPS) rather than to a direct effect of CPS. Tumor necrosis factor activity was not detected in the culture supernatants of bovine monocytes incubated with purified CPS for 1-18 h in vitro.