Quantitative Estimation of Antibody in the Immunoglobulin Classes of the Mouse

Thymectomized mice produced a significantly lower level of antibody against human serum albumin (HSA) and the decrease in total antibody activity was due to a decrease in the IgG1 while the other immunoglobulin classes were largely unaffected. The same animals did produce a normal response in all immunoglobulin classes to a high dose of keyhole limpet hemocyanin (KLH). However, a low dose (1 µg) of the same antigen produced a poor response in thymectomized mice, and, as was found with HSA, IgG1 was the main immunoglobulin class affected. It is concluded a) that KLH is a “non-thymic-dependent” antigen only at a relatively high dose and b) that of all the immunoglobulin classes only IgG1 is thymic-dependent.