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The effect of serum inhibitor on the antigenic and mitogenic responses to E. coli bacteria.

The effect of serum inhibitory factors on the induction of the in vitro immune response and mitogenic response to Escherichia coli antigens in murine spleen cell cultures was investigated. Both normal and congenitally athymic mice served as spleen cell and serum donors. Cultured CBA/J spleen cells produced anti-bacterial antibody in the presence of mouse serum, but the mitogenic response to the bacterial antigen was suppressed by the addition of mouse serum. The addition of mouse serum from either CBA/J or nude mice to nude spleen cell cultures led to suppression of both the antigenic and mitogenic responses to bacterial antigen. The polyclonal antibody response by CBA/J spleen cell cultures to SRBC induced by bacteria was significantly enhanced by the addition of either CBA/J or nude mouse serum. Conversely, the nude spleen cell polyclonal response to SRBC was significantly inhibited by high concentrations of nude or CBA/J mouse serum. These data indicate that inhibition of the specific E. coli and nonspecific polyclonal antibody responses by mouse serum occurs only in cultures of spleen cells taken from mice lacking a population of T lymphocytes.