Two IgG1 (IgF) subclasses in mice: presence in normal serum and representation within lymphocyte and plasma cell populations.

Monospecific anti-gamma1 sera were prepared in rabbits against each of two IgG1 mouse myeloma globulins isolated from myeloma A2 and MOPC21. Both these sera react with IgG1 of normal mouse serum by immunoelectrophoresis and cannot be distinguished any further. The antibodies contained in the sera were cross-isolated on immunoadsorbents containing either the A2 or MOPC21 antigenic material and tested by immunoelectrophoresis against normal mouse serum. An interesting spur was formed between these two antibodies. The two isotypes thus revealed in normal serum are tentatively designated IgG1a (globulin A2) and Ig G1b (globulin MOPC21). With live peripheral lymph node cells almost all lymphocytes which stain with antikappa antibodies (B lymphocytes) also stain with the specific anti-gamma1a antibodies, but only 5-10% stain with the specific anti-gamma1b antibodies. On fixed spleen cells (C57B16 mice) the anti-gamma1a antibodies stain almost identical percentages of plasma cells as anti-kappa antibodies: 1.8% are gamma1 and 2.2% are kappa. Anti-gamma1b antibodies stain only 5% of kappa-positive plasma cells. The % values estimated on both the normal lymphocyte and plasma cell populations were not significantly affected by inhibtion experiments of the specific anti-gamma1 antibodies performed with isolated myeloma globulins representative of several Ig classes.