Increased expression of alkaline phosphatase activity in stimulated B lymphocytes by muramyl dipeptide.

We have recently shown that the synthetic immunomodulator muramyl dipeptide (MDP) acts on murine B lymphocytes. It synergizes with interleukin 2 and interleukin 4 to stimulate, respectively, the differentiation and the proliferation of B cells. In the present study, MDP was shown to increase the proliferation of B cells stimulated by lipopolysaccharide (LPS). Moreover, the expression of alkaline phosphatase activity induced by LPS was markedly enhanced by MDP. These effects were time- and dose-dependent. The present report suggests that the biochemical mechanism by which MDP exerts its effects may involve protein phosphorylation-dephosphorylation pathways.