Listeria cell wall fraction: a B cell adjuvant

A crude cell wall-rich fraction of Listeria monocytogenes (LCWF) has previously been shown to induce resistance to Listeria infection in mice, to be a murine B cell mitogen, and to be an immunologic adjuvant. Data reported here show that LCWF stimulates immune responses by three different murine B cell populations that respond poorly or not at all to thymus-dependent antigens when T cells are severely depleted or absent. These B cell populations include nude mouse spleen cells, anti-theta serum-treated spleen cells and bone marrow-derived spleen cells. In addition, sheep erythrocytes coated with LCWF are converted to thymus-independent antigens. The adjuvant effect of LCWF on B cell populations is not enhanced by the presence of T cells, nor does LCWF increase in vivo education of T cells to sheep erythrocyte antigens. Thus, a direct effect of LCWF on T cells could not be demonstrated, suggesting that LCWF does not act on T cells. Because of these LCWF effects on B cells, the possible role of B cells in resistance to infection by Liseria monocytogenes is discussed.