Methotrexate and colchicine administered during a primary response to S. adelaide in mice both preferentially inhibit γG antibody formation. In these experiments, the γM and γG antibody responses seem to be independent of one another. The γM antibody response is not prolonged by the immediate absence of a following γG response. Also, the γG antibody response is able to recover from the effects of both drugs and reach near-normal serum titers whether or not there is a preceding γM response.

During a methotrexate inhibited response, normal levels of γM can occur in the serum at a time when no pyroninophilic blast cells or secondary nodules are evident in the spleen. The recovery of γG production is well correlated with the appearance of many hemocytoblasts in the splenic red pulp, although no secondary nodules or mature plasma cells can be found at this time.

A study has also been made of γM and γG antibody production in x-irradiated recipients after transfer of spleen cells from primed animals. When spleen cells are taken from immunized donors on day 2 or day 6 after injection of antigen, only γM antibody can be demonstrated in the recipients. Spleen cells taken on day 8 or day 10 after antigen produce mostly γG antibody in the recipients.

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