Functional maturation of immature B cells accumulated in the periphery by an intraperitoneal administration of a traditional Chinese medicine, xiao-chai-hu-tang (Japanese name: shosaiko-to)

We found that an intraperitoneal (ip) injection of a traditional Chinese herbal medicine, xiao-chai-hu-tang (Japanese name: shosaiko-to), induced accumulation of B lymphocytes (sIgM+) in the peritoneal cavity and spleen. 1) Cell surface marker analysis by a fluorescence-activated cell sorter (FACS) demonstrated that the accumulated B cells on day 4 or 7 after shosaiko-to administration (early phase) were composed mainly of sIgM+IgD- cells and suggested that these B cells maturated into sIgM+IgD+ cells on days 10 or 14 (late phase). Relative decrease of IgM+IgD+ cells at early phase was more profound in peritoneal cells (PC) than in spleen cells. 2) With respect to spleen lymphocytes, antibody responses to a thymus-independent (TI) antigen of type 2 (trinitrophenylated Ficoll) and a thymus-dependent (TD) antigen (sheep erythrocyte) were enhanced at late phase but not at early phase. In contrast, responses to trinitrophenylated lipopolysaccharide (TNP-LPS) as a TI-1 antigen and LPS as a B cell mitogen or a polyclonal B cell activator were enhanced markedly at early phase but declined at late phase. 3) With respect to peritoneal lymphocytes, responses to LPS were suppressed at early phase but recovered at late phase. Enhanced responses to TI and TD antigen at late phase in spleen lymphocytes and suppressed response to LPS at early phase in peritoneal lymphocytes may be explained by increases of IgM+IgD+ mature B cells and IgM+IgD- immature B cells, respectively, at those times. Enhanced responses to TI-1 or LPS in spleen lymphocytes at early phase may be explained by elevated sensitivity of IgM+IgD+ cells which reside in the spleen before shosaiko-to administration and receive the direct stimulation by shosaiko-to, or by acquired responsiveness of IgM+IgD- cells which migrate after stimulation with shosaiko-to.