Modulation of mitogenic responsiveness by staphylococcal peptidoglycan.

Staphylococcal peptidoglycan can modulate in vivo and in vitro antibody responses and is a B-cell mitogen. The effect of in vivo peptidoglycan treatment on the subsequent in vitro mitogenic responsiveness of mouse splenocytes to phytohemagglutinin, concanavalin A, pokeweed mitogen, and lipopolysaccharide was studied by measuring changes in deoxyribonucleic acid synthesis. Injection of peptidoglycan caused a 100% increase in responsiveness to phytohemagglutinin and pokeweed mitogen and a 45% increase in responsiveness to concanavalin A. Responsiveness to lipopolysaccharide was decreased by 40%. Increased phytohemagglutinin and decreased lipopolysaccharide responses were not due to changes in the kinetics of the response or optimal concentrations of these mitogens. Increased responsiveness to phytohemagglutinin lasted for 2 weeks after peptidoglycan injection. Neither increased background deoxyribonucleic acid synthesis nor changes in the proportion of T cells after peptidoglycan treatment fully accounted for the changes in responsiveness to the mitogens. In vitro costimulation with peptidoglycan and phytohemagglutinin, lipopolysaccharide, concanavalin A, or pokeweed mitogen resulted in interference of the response. Cell separation experiments indicated that peptidoglycan-induced modulation of mitogenic responsiveness was mediated by B lymphocytes.