Marked reduction of mouse peritoneal CD5⁺ B cells by intraperitoneal administration of lipopolysaccharide

Intraperitoneal administration of lipopolysaccharide to mice induced a marked reduction of CD5⁺ B cells in the peritoneal cavity. The reduction was not induced by intravenous, subcutaneous, or oral administration of lipopolysaccharide. The reduction continued for about 10 days after the injection, and the CD5⁺ B-cell count recovered to the normal state about 14 days after the injection. The reduction of peritoneal CD5⁺ B cells might be caused by apoptotic cell death. Injection of lipopolysaccharide did not result in production of antibody to lipopolysaccharide. On the other hand, intraperitoneal injection of heat-killed bacteria did not induce a reduction of peritoneal CD5⁺ B cells and elicited the definite production of antibody to lipopolysaccharide.