Local immune response in experimental pyelonephritis in the rabbit. II. Lymphocyte stimulation by lipopolysaccharide of infecting organism.

The response of circulating and kidney lymphocytes from rabbits with experimental haematogenous pyelonephritis to somatic (O) antigen (lipopolysaccharide) from the infecting organism was evaluated. Lymphocytes were cultured for 3 days in the presence and absence of lipopolysaccharide from the infecting organism, Escherichia coli O75 and a heterologous organism. Circulating lymphocytes showed a significant response to the homologous lipopolysaccharide by day 5 of infection, and kidney lymphocytes responded by day 19 of infection but failed to respond after day 33. The lipid moiety of somatic antigen was required for the stimulation of lymphocytes since antigen preparations in which lipid was low or absent did not activate lymphocytes. B lymphocytes from kidney were stimulated by this antigen whereas both T and B circulating lymphocytes responded. Thus, pyelonephritis in rabbits is associated with the activation of a subpopulation of circulating cells which have specific receptors for the homologous antigen. B lymphocytes that are specifically activated by the homologous or O antigen then localize to the infected site.