Listeria cell wall fraction. Characterization of in vitro adjuvant activity.

We have previously described a crude cell wall fraction of Listeria monocytogenes (LCWF) which induces resistance to listeria infection in mice, is a murine B-cell mitogen and is an immunological adjuvant. Data reported here show that LCWF, which is effective over a wide dose range, exerts its adjuvant action on early events in the induction of an immune response. Moreover, LCWF stimulates nonadherent cells to respond to sheep red cells when adherent cells are severely depleted or absent, suggesting that LCWF can therefore act directly on lymphocytes present within the non-adherent population.