Activated complement c 1 inhibitor dependent dissociation of human activated complement c 1 bound to immune complexes
Sim, R.B.; Arlaud, G.J.; Colomb, M.G.
Biochemical Journal 179(3): 449-458
ISSN/ISBN: 0264-6021 Accession: 004662015
The interaction of C.hivin.1 [activated 1st complement component] inhibitor with complement component C.hivin.1 bound to immune complexes was examined by using 125I-labeled C.hivin.1 subcomponents. The inhibitor bound rapidly to subcomponent C.hivin.1s and more slowly to subcomponent C1.hivin.r. Formation of the C1.hivin.r-C.hivin.1 inhibitor complex caused rapid dissociation of subcomponents C1.hivin.r and C1.hivin.s from the antibody-antigen-component C.hivin.1 aggregate. The rate and extent of this release were proportional to C.hivin.1 inhibitor concentration and were also dependent on ionic strength. Results obtained with purified C.hivin.1 inhibitor, plasma or serum as source of C.hivin.1 inhibitor were closely comparable. Only slight dissociation of subcomponent C1q was observed under the same range of conditions. The implications of the release phenomenon were discussed in relation to the structure of component C.hivin.1 and the possibility of differential turnover of C.hivin.1 subcomponents.