Activation of complement c 1 the generation of complement c 1r c 1s and activated complement c 1 inactivator complexes in normal serum by heparin affinity chromatography
Mckay, E.J.; Laurell A B.; Martensson, U.; Sjoholm, A.G.
Molecular Immunology 18(5): 349-358
Investigations facilitating heparin-affinity chromatography and immunochemical procedures were utilized to study the interaction and behavior of heparin with [human complement] C1, C1 subcomponents and C.hivin.1 IA [activated C1 inactivator] in normal serum. At physiological pH and salt concentration, C1q bound to heparin-Sepharose independent of divalent cations at 4 and 37.degree. C and a high salt concentration was required for its complete release. Macromolecular C1 bound to heparin-Sepharose in the presence of Ca2+ at 37.degree. C, activating C1r and C1s in the process as demonstrated by the appearance of C.hivin.1r-C.hivin.1s-C.hivin.1 IA complexes when purified C.hivin.1 IA was added to the eluted fractions. At 4.degree. C, proenzyme C1r and C1s were present in the eluted fractions. Proenzyme C1r-C.hivin.1s and C.hivin.1r-C.hivin.1s-C1 IA complexes did not bind directly to heparin-Sepharose. Binding of C1r-C1s in the presence of Ca2+ was dependent on C1q bound to heparin. High levels of proenzyme C1r-C1s complexes were produced during the 4.degree. C experiments in the presence of Ca2+ and were collected in the void volume. C.hivin.1r-C.hivin.1s-C.hivin.1 IA complexes generated during the 37.degree. C experiments had no affinity for heparin-Sepharose. C.hivin.1 IA did not bind directly to heparin. Recirculation of a serum sample collected after C1q was removed by heparin-affinity at 4.degree. C in the presence of EDTA demonstrated that: C1r and C1s in the presence of Ca2+ could be reassembled with heparin-bound C1q to form macromolecular C1; C1r and C1s in non-activated forms did not bind directly to heparin-Sepharose; and C1r and C1s contained in the reassembled C1/heparin complex at 37.degree. C were in active forms.