Abstract
We have studied the effects of polyclonal monospecific Fab' preparations against CĪr, CĪs, CĪINH, C4, C4bp, and fragment Bb of factor B on complement activation in NHS and HAES. Furthermore, we have investigated complement activation in these sera after addition of purified Cls and purified C4bp. Blocking CĪINH induced a spontaneous activation of the classical pathway in NHS and to a lesser extent in HAES. Addition of p-CĪs resulted in a strong C3 conversion in NHS, but not in HAES. However, after the blocking of C4bp in HAES, addition of p-CĪs produced a total C3 consumption. The ratio of the protein concentration of C4bp to hemolytically active C4 was eight times higher in HAES than in NHS. This increased ratio may account for the resistance of HAES to the CĪs induced C3 cleavage in our in vitro system and the stability of C3 in HAE despite C4 and C2 consumption in vivo.