Breakdown products of C3 and factor B in hemolytic-uremic syndrome.

Serum concentrations of Clq, C4, C3, and Factor B but not properdin were significantly decreased in patients with HUS compared to values in normal control subjects (p value less than 0.01). Sera from 13 HUS patients obtained early after the onset of the disease showed breakdown products of Factor B (Ba, Bb) by immunoelectrophoresis; 12 of these sera showed C3 breakdown products (C3c, C3d). Sera from seven patients studied 1 month to 3 years later no longer demonstrated any breakdown products of Factor B or C3. These data suggest that the complemented system is activate in HUS. The concept that immunological mechanisms play a major role in this disease is additionally supported by the occurrence of IgM, C3, and fibrin in glomeruli and renal vessels.