The effect of RU 41740 on the in vitro maturation of human B-cells

We have tested the effect of a Klebsiella pneumoniae extract, RU 41740, and its lipopolysaccharidic fraction (LPS-LAP) on the in vitro activation of human B-cells. Two models have been used: the polyclonal activation induced by pokeweed mitogen and the specific antibody production to mannan, a polysaccharide extracted from the cell wall of Candida albicans. We have shown that RU 41740, and especially its lipopolysaccharidic fraction, significantly increases the production of immunoglobulins and specific antibodies. This effect is mediated by T-lymphocytes, since preincubation of isolated T-cells, but not of non-T-cells, resulted in the same effect. Together with the known enhancing effect of LPS-LAP on T-cell proliferation, these data strongly suggest that LPS-LAP increases the production of B-cell-activating lymphokines by T-cells.