COMPLEMENT ACTIVATION IN ASYMPTOMATIC PATIENTS WITH SICKLE-CELL ANEMIA

  • 1 January 1979
    • journal article
    • research article
    • Vol. 36  (1) , 130-139
Abstract
Previous reports suggested that a defect in serum complement [C] may contribute to the increased susceptibility to infection shown by patients with sickle cell anemia (SCA). To define the nature of any C abnormality in SCA, the C system was investigated in 87 patients during asymptomatic periods and factor B turnover in a small sample was analyzed. In these patients geometric mean serum concentrations of functionally active factor B and factor D and of C3 [complement component 3] and C4 protein (expressed as a percentage of normal reference serum) were lower than in controls (78% vs. 107%, P < 0.001, 86% vs. 103%, P < 0.001, 91% vs. 100%, P < 0.01, 89% vs. 105%, P < 0.05, respectively). The ratio of the serum concentration of functionally active factor B to factor B protein was lower in patients than in controls (mean 75% SD 16% vs. mean 93%, SD 22% P < 0.001), indicating a functional deficiency of factor B protein. The fractional catabolic rate of radiolabeled factor B was markedly increased in 4 out of 7 asymptomatic patients studied and was inversely related to the functional factor B concentration in serum (r [correlation coefficient] = -0.59, P < 0.05). Factor B synthesis was uniformly increased. C activation was not related to the presence of circulating C1q [q fragment of C1] binding material. C activation, rather than defective synthesis as previously suggested, contributes to the abnormalities in C component concentration and function in asymptomatic subjects with sickle cell anemia.