Studies on the thymic dependence of the immunoglobulin classes of the mouse (38570).

The influence of the thymus on serum immunoglobin (Ig) concentration was studied by a comparison of serum Ig levels in congenitally athymic (nu/nu) mice versus control littermate heterozygotes and adult thymectomized, irradiated, bone marrow reconsituted mice (ATx plus B) versus adult thymectomized, irradiated mice reconstituted with bone marrow and thymus (ATx plus BT). IN THE FORMER GROUP IgGl. IgA, and IgG2a were 8%, 17% and 31% of controls. IgM levels were increased (340%) compared to controls. When ATx plus B mice were compared to controls. When ATx plus B mice were compared with nonirradiated controls sigificant depressions were noted in serum IbGl and IgM. The only significant decrease in serum Ig levels between ATx plus B and ATx plus BT was in IgGl. These results are discussed in terms of the effects of thymic influence, residual T lymphocyte population differences between the two groups, and the effect of irradiation.