Formation of complexes composed of activated complement c 1r activated complement c 1s and activated complement c 1 inactivator in human serum on activation of complement c 1
Laurell, A.B.; Johnson, U.; Martensson, U.; Sjoholm, A.G.
Acta Pathologica et Microbiologica Scandinavica Section C Immunology 86(6): 299-306
C1 [complement component 1] subcomponent complexes in normal serum incubated with C1q binding substances, or with proteolytic enzymes were studied by crossed immunoelectrophoresis. C.hivin.1r [activated C1r], C.hivin.1s, trypsin, heat-aggregated Ig[immunoglobulin]G, immune complexes, cell-bound antibody or complexes of C-reactive protein with protamine sulphate gave rise to dissociation of C1 and the appearance of C1s protein in the .alpha.2 position. Plasmin, DNA and [Escherichia coli] endotoxin did not affect the normal C1s protein pattern. Following incubation with C.hivin.1r, C.hivin.1s, trypsin, or complexes containing C-reactive protein, the C1q in serum was found in a cathodal position similar to that of purified C1q. The C1s protein in the .alpha.2 position was part of a complex composed of C1r, C1s and C.hivin.1 inactivator proteins. C1r in the complex was detected immunochemically by using anti C1r and anti C1s in combination. The complex had a MW of about 5 .times. 105 daltons. Complexes of C1r, C1s and C.hivin.1 inactivator proteins in serum are formed on C1 activation; the complexes may contain activated C1r and C1s (C.hivin.1r-C.hivin.1s-C.hivin.1 IA). C1r-C1s complexes with .beta.1 mobility were not formed in vitro. .beta.1 C1r-C1s complexes in pathological sera could be converted to C.hivin.1r-C.hivin.1s-C.hivin.1 IA by treatment with C.hivin.1r and C.hivin.1s and also, provided C1q was available in serum, by treatment with heat-aggregated IgG. .beta.1 C1r-C1s complexes in serum contain C1r and C1s in proenzyme form.