Studies on lipopolysaccharide-induced polyclonal B cell activity in mice tolerized by sheep red blood cells and cyclophosphamide.

The polyclonal immune response was induced in untreated mice and mice treated with cyclophosphamide by the administration of lipopolysaccharide from E. coli or S. marcescens. The number of cells forming antibodies to sheep red blood cells and to trinitrophenyl, and of cells producing immunoglobulins increased. The administration of LPS to mice pretreated with SRBC and CY (tolerant mice) considerably reduced the number of anti-SRBC AFC in comparison with the controls. The tolerogenic treatment did not change the number of anti-TNP AFC and IPC. Analogous results were obtained in genetically athymic (nude) mice and in B mice (thymectomized, lethally irradiated and reconstituted with embryonic liver cells). The results suggest that a deletion or a temporary inactivation of a fraction of the antigen-specific B cells occurs in tolerant mice. This inactivation cannot be explained by the absence of expression of surface immunoglobulins on B cells nor by the activity of suppressor T cells.