Effect of outer membrane proteins from Shigella on humoral immunity induced in mice by SRBC.

Shigella flexneri outer membrane proteins (OMP) which had been earlier found to exert immunomodulatory effect on cell mediated immune response were also found to act as immunomodulator of the humoral immune response. Effects of OMP were investigated in the experiments in vitro and in vivo, where the level of humoral immune response, measured as the number of plaque-forming cells (PFC) to SRBC in the spleen was evaluated. We demonstrate that small doses of OMP (1-5 micrograms) stimulate, whereas higher doses (10-50 micrograms) suppress the humoral immunity.