Solubilization of IgA Immune Precipitates by Complement

The complement (C) system can solubilize immune precipitates prepared with antibodies of the IgG class, and apparently also of the IgM class. This paper shows that C can also solubilize immune precipitates prepared with two different antigen-binding IgA myeloma proteins. Immune precipitates were prepared with a) mouse myeloma protein TEPC 15 and PC-KLH, and b) mouse myeloma protein MOPC 315 and DNP-BSA. The precipitates could be solubilized by fresh mouse serum, but not by zymosan- or heat-inactivated serum. The rate of solubilization was not affected by the removal of of Ca++ ions. These results verify that the C-mediated solubilization effect can proceed entirely via the alternative C pathway, and lend increased support to the view that the effect is a general phenomenon, not restricted to a particular antibody class or type of antigen.