Failure of IgA cold agglutinin to activate C.
No complement (C) activation was observed when IgA cold agglutinin was reacted with its antigen on RBC. Neither C-consumption (CH50) nor C1 binding (classical pathway) nor conversion of factor B or C3 (alternative pathway) could be detected. In contrast, IgM cold agglutinins under the same conditions did activate the classical pathway. If the IgA was heat aggregated it was able to activate the alternative pathway as evidenced by factor B and C3 conversion. The result is consistent with the absence of in vivo hemolysis in patients with IgA cold agglutinins.
D001323:Autoantibodies / Q000276:immunology*; D003167:Complement Activation; D003172:Complement C1 / Q000276:immunology; D003176:Complement C3 / Q000276:immunology; D003170:Complement Pathway, Alternative; D003171:Complement Pathway, Classical; D003450:Cryoglobulins / Q000276:immunology*; D006801:Humans; D007123:Immunoelectrophoresis, Two-Dimensional; D007070:Immunoglobulin A / Q000276:immunology*; D007075:Immunoglobulin M / Q000276:immunology; D010265:Paraproteinemias / Q000276:immunology*; D012397:Rosette Formation
D001323:Autoantibodies; D003172:Complement C1; D003176:Complement C3; D003450:Cryoglobulins; D007070:Immunoglobulin A; D007075:Immunoglobulin M