Further Evidence for Macromolecular Nature of Human C′l

Abstract

C′l activity of human complement has been shown by Lepow et al.¹ to require three chromatographically isolated proteins: C′lq, C′lr and C′ls. The C′lq component was identical to the 11S protein, originally described by Müller-Eberhard and Kunkel² and Taranta et al.³. C′lr was a previously undescribed protein and C′ls the known pro-esterase. Further experiments demonstrated that these sub-components formed a macromolecule in the presence of calcium with a sedimentation coefficient of 18, whereas in sodium ethylenamine tetraacetate (NaEDTA), C′l dissociated into its three sub-components, C′lq, C′lr and C′ls (ref. 4), with sedimentation coefficients of 11S, 7S and 4S, respectively. The macromolecular nature of C′l was obtained by haemolytic data alone, and so the following experiments were designed to demonstrate these differences in sedimentation utilizing an antiserum specific for the 11S protein or C′lq.