C1Q BINDING SUBSTANCES IN PEMPHIGUS AND BULLOUS PEMPHIGOID - DETECTION WITH A [C1Q-I-131] BINDING ASSAY

  • 1 January 1977
    • journal article
    • research article
    • Vol. 28  (1) , 40-48
Abstract
A modification of the [125I]C1q [q fragment of the 1st complement component] binding assay was developed to allow the estimation of C1q binding activity (C1qBA) in pemphigus and bullous pemphigoid sera. The modifications include lower final concentration of PEG 6000 [polyethylene glycol] (1.5%) (which permitted the use of sera that was stored at -20.degree. C for extended periods of time), use of 131I instead of 125I, and an [131I] C1q concentration of 5 .mu.g/ml rather than 1 .mu.g/ml. EDTA was used at a final concentration of 0.13 M to obviate the need for heat inactivation of sera. Sera from 71 patients with pemphigus and from 142 patients with bullous pemphigoid were tested for C1q BA. Of these, 40% of the pemphigus and 20% of the bullous pemphigoid patient showed elevated C1q BA. A relationship between elevated C1q BA in serum and active disease was noted. Sequential samples from 40 patients with pemphigus and 37 patients with bullous pemphigoid demonstrated 2 different types of relationship between serum antibody titers and C1q BA. In some patients serum antibody titers and C1q BA increased and decreased simultaneously; in others, increase of C1q BA followed increase of antibody titer and coincided with its decrease. C1q BA may represent, at least in part, antigen-antibody complexes containing cutaneous antigens.

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