Crossed Immunoelectrophoresis of Human C3 : Electrophoretical Heterogeneity among Purified Molecules

One component of complement system, C3, is detected in β region electrophoretically. Purified C3 has a molecular weight of 187500, and has been considered to have a homogeneous physicochemical structure. The authors intend to mention in this paper about the observations which suggest the heterogeneity among molecules of human C3 in solution. Crossed immuoelectrophoresis, using anti-human C3 serum (rabbit or goat), detected at least 5 precipitation arcs in β1c globulin (C3), and this pattern of electrophoresis was observed in repeated experiments. When human serum was used as the source of C3, the same electrophoretic pattern as that of purified C3 was detected. Recently, correlation between some conformational changes of C3 molecules and the appearance of C3b-like functional properties was reported by some investigators. The relationship between our data and these conformational changes is unclear and requires further investigation. Our results suggest that standard semi-quantitative calculation of C3 conversion ratios could be mistakenly high because of the existence of several sub-arcs in the βlc arc, and that such calculation require quantitative consideration of the sub-arcs.

Ueki A, et al