Immunoglobulin class and subclass levels in the serum of CBA mice throughout life.

The levels of IgA, IgM, and the four subclasses of IgG in the serum of CBA mice of different ages were measured by the Sepharose bead immunofluorescence assay. The developmental curves of the CBA serum levels indicate three periods in the life of the mice during which changes occur. The respective adult levels of the different Ig's are reached during the first 6 months. Between 6 and 24 months of age, individual class and subclass levels do not show much change, except for the IgG1 and IgG2b subclasses, which clearly increase. The last period, from 24 months on, is characterized by great variation among the Ig levels of individual animals, while the mean levels do not show distinct trends. Although some differences between the levels of Ig's of female and male mice were observed at certain ages and for certain Ig's, no systematic trend was clear. The generally recognized age-related decline in immunocompetence is thus not accompanied by decreasing levels of serum immunoglobulins.