ACTIVATION OF THE CLASSICAL PATHWAY OF COMPLEMENT BY THE C3NEF-STABILIZED CELL-BOUND AMPLIFICATION CONVERTASE

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  • 1 January 1979
    • journal article
    • research article
    • Vol. 122  (3) , 801-805
Abstract
C3 [complement component 3] nephritic factor (C3NeF) is composed of 2 H and 2 L chains like Ig[immunoglobulin]G. It also shares antigenic determinants with IgG. C3NeF, purified from the sera of 8 patients by incorporation of C3NeF into the stabilized fluid phase amplification C3 convertase, C3b,Bb(C3NeF), followed by its release after decay of convertase function, was investigated for its ability to bind 125I-C1q and to activate 125I-C1. Although fluid phase C3b,Bb(C3NeF) is fully capable of binding 125I-C1q, it cannot activate 125I-C1, even at concentrations of 1.3 .times. 1012 C3b,Bb(C3NeF) complexes/ml. Cell-bound C3b,Bb(C3NeF) is capable of binding 125I-C1q and activating 125I-C1. This discrepancy between fluid phase and cell-bound C3b,Bb(C3NeF) was found for C3NeF preparations from 8 different patients and seems to apply to all C3NeF preparations. [C3NeF is found in sera of patients with membranoproliferative glomerulonephritis and partial lipodystrophy.].