Immunoglobulins in intact, immunized, and contaminated axenic mice: study of serum IgA.

The study of immunoglobulin levels of intact, immunized and/or contaminated axenic mice showed that: 1) axenic mice had lower levels of serum IgG2 and IgG1 than did holoxenic mice, but both immunoglobulin levels rose sharply after immunization or contamination of the former. In contrast, serum IgA remained undetectable in axenic mice after immunization and at 21 days after contamination; 2) serum IgA appeared about 2 months after massive contamination of axenic mice or 6 days after administration of prednisolone to them. The effect of prednisolone on serum IgA seemed to be related to passage of IgA from the intestinal system into the blood without true activation of the serum system.