[The relationship between the number of antibody forming cells in the spleens of rats immunized with Sal. typhi O-antigen and the number of background cells producing antibodies to that antigen].

It was shown on 5 series of rats by the method of local passive hemolysis in gel that the number of antibody-forming cells (AFC) in the spleen after the immunization with O-antigen from Sal. typhi correlated with the number of background AFC to the given antigen in the animals of the same series. This, possibly, pointed to the fact that the number of spontaneous AFC reflected the number of B-lymphocyte immunocompetent to the given antigen and could be used - to some extent - for the assessment of the immunological reactivity to this antigen before the immunization.