Relationship of Immunoglobulin to Complement Receptors of Human B Cells

By using the disappearance of the surface Ig from human peripheral lymphocytes as a parameter of modulation, at 37°C it was shown that anti-Fab antibody is a more effective and faster modulator of the surface Ig than anti-Fc, anti-IgM, or anti-IgG antibodies. The C-binding site was demonstrated to be fully independent and distinct from the surface Ig and a stable marker of Ig-bearing cells. The C receptor can be blocked by the addition of fresh C5-sufficient, C5-deficient mouse serum, or fresh autologous human serum, at 37°C before binding to EAC by a mechanism still to be defined. Both IgM and IgG cells possess the C receptor. The relationship of Ig to C receptors and their role in cell activation by the specific antigen is discussed.