Immunoglobulins in NZB-BL mice. I. Serum immunoglobulin levels and immunoglobulin class of erythrocyte autoantibody.

Determination of serum immunoglobulin levels in NZB and normal mice has indicated that an elevation of the gammaM-globulin level occurs in NZB mice. This can be demonstrated in young NZB mice well before other autoimmune manifestations are observed. A slight elevation of gammaM-globulin was also observed in NZB hybrid mice. Erythrocyte autoantibodies were analyzed by the direct Coombs' test with specific antiimmunoglobulin reagents. Autoantibodies in NZB mice can be of all immunoglobulin classes, although predominantly of gammaG(1)-class. In (NZB x NZC)F(1) hybrid mice, although Coombs' positivity develops around the same age as in NZB mice, there is a greater restriction of the autoantibodies into gammaM- and gammaG(1)-classes. Preliminary attempts to quantitate immunoglobulins coating NZB red cells have shown that there are approximately 400 molecules of gammaM and 5000 molecules of gammaG-globulin per NZB mouse red cell.