FURTHER-STUDIES OF THE C3G COMPONENT OF THE ALPHA-2D FRAGMENT OF HUMAN C-3

Abstract

Recent studies led to the discovery of a new C3b breakdown product antigen, C3g, which is present on the .alpha.2D fragment of C3 but is removed by trypsinization. Studies were undertaken to confirm findings in entirely human red cell an serum systems, including studies on cells from 9 patients with a variety of complement-mediated autoimmune hemolytic anemias. The results confirm the recently reported findings. The presence of both C3d and C3g on all patient''s red cells so far tested supports the concept that red cells coated by C3d alone are likely to be a laboratory artefact and that the .alpha.2D fragment (C3d,g) is the natural end product of cell bound C3b breakdown in vivo.