The five classes of immunoglobulins in normal C3H and BALB/c mice.

The five major classes of mouse immunoglobulin have been purified and, by appropriate immunization of goats, monospecific antisera have been obtained. With these antisera the five classes of mouse immunoglobulin have been quantitated in the serum of normal C3H and BALB/c mice from birth to the end of the first year of life. Newborn mice of both strains have shown no IgA or IgM in their serum by the method used. Except for IgM, all immunoglobulins have shown a rapid increase a few days after birth, followed by a decline to lower levels at approximately 20–30 days of age. These changes have been observed by others and attributed to transfer of IgG1, IgG2 and IgA by colostrum and milk, but changes in the lymphoreticular apparatus are also occurring at this time which could contribute or account for some of these fluctuations. After the age of 60–80 days BALB/c mice are very often hyperglobulinaemic. This hyperglobulinaemia can be attributed to the increase in IgG1, IgM and partly IgG2b.