The attachment of serum- and plasma-derived C3 to solid-phase immune aggregates and its relation to complement-mediated solubilization of XXXX .

@entity1 @entity7110 @entity1025 @entity1792 @entity4417 @entity8428 @entity141
The interaction between immune aggregates and complement (C) was investigated. Solid-phase immune aggregates were prepared by coating microwells with heat-aggregated bovine serum albumin (BSA) followed by rabbit anti-BSA antibody. The immune aggregates were reacted with human serum or citrated plasma at 37 degrees C. The binding of C3 components was investigated with biotinylated F(ab')2 antibodies to C3c and @entity8428 and avidin-coupled alkaline phosphatase. The form of the incorporated C3, whether @entity4417 -iC3b or C3dg, can be deduced from the response with these two antibodies. The maximal binding of @entity4417 -iC3b to the immune aggregates was observed within 5 min of incubation with serum or citrated plasma. The conversion to C3dg was evident by a decrease in bound anti-C3c concomitant with increasing anti- @entity8428 reactivity within about 10 min of incubation. When the classical C pathway activation was inhibited, the binding of @entity4417 -iC3b was delayed by 20-30 min, whereas stopping of the alternative pathway did not influence the initial kinetics of the reaction. The addition of @entity1 red blood cells had no measurable influence on the degradation of bound @entity4417 -iC3b. 125I-labelled anti-BSA antibody bound to the solid-phase BSA was not released during the C3 incorporation. The incorporation of @entity4417 into the immune aggregates was mediated equally well by serum and by citrated plasma. The incorporation of @entity4417 -iC3b into @entity7110 ( @entity7110 ) is thought to be responsible for the C-mediated solubilization (CMS) of @entity7110 . Citrated plasma, however, exerted no CMS capacity when measured by a radiometric assay. The CMS capacity of serum was inhibited by @entity1792 , but could then be restored by adding @entity141 and @entity1025 , whereas no CMS could be demonstrated with citrated plasma to which divalent metal ions were added.
