Complete absence of the third component of complement

A 4 yr old female patient who had recurrent infections with encapsulated bacteria and gram negative organisms was found to have no C3. All other C components were present in normal amounts immunochemically and hemolytically except for a moderately reduced hemolytic C4. By Ouchterlony analysis, the patient's serum contained C3b inactivator and properdin but no antigenic C3. Activation of the alternative pathway was examined by purified cobra venom factor (CVF) and inulin. Neither of these substances led to activation of B → B except when partially purified C3 was added. Immune adherence was found to be normal in the patient's serum and could be removed by anti C4 antiserum or hydrazine treatment. A marked opsonic defect was present against E. coli. Serum bactericidal activity against a rough strain of E. coli was also defective. The ability to mobilize an inflammatory response was examined by Roebuck skin window technique. A delay in neutrophil migration occurred until the sixth hour. In vitro lymphocyte transformation and serum immunoglobulins were normal. The proportion of peripheral blood T cells forming spontaneous sheep erythrocytes and the percentage of B cells forming EAC rosettes by C3 receptor were normal. The recurrent infections with encapsulated and gram negative organisms are consistent with the absence of C3.