PubMed · 53416
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P Trouillas, G Aimard, F Berthoux, M Devic. 1975-11-08. Letter: Multiple sclerosis with hypocomplementaemia.. https://doi.org/10.1016/s0140-6736(75)92176-5
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C3 breakdown products were measured in 51 fresh and stored sera and/or EDTA plasma samples from 18 healthy subjects, 8 patients affected by essential mixed cryoglobulinaemia, and 15 patients with miscellaneous glomerulonephritis, by simultaneous crossed immunoelectrophoresis and immunofixation. C3 splitting products, as determined by both methods compared well, and showed a highly significant correlation. The advantages and reliability of these two methods are discussed. Immunofixation seems to be the most suitable for routine use in clinical practice, being less expensive and more rapid to perform.
Two forms of C4-binding protein (C4-bp) (C4-bp low, C4-bp high), which differ slightly in net charge and apparent molecular weight, as determined by SDS- PAGE, were separated by ion-exchange chromatography and contaminants removed with specific antisera. Both forms of C4-bp served as cofactors for the cleavage of C4b in solution by C3b inactivator, and the resulting fragments of the a'-chain of C4b had identical molecular weights. In addition, similarly to beta1H, C4-bp low or high served as cofactors for the cleavage of fluid phase C3b by C3bINA. However, important quantitative differences between the activities of C4-bp and beta1H were observed. With regard to C3b in solution, the cofactor activity of beta1H was {approximately equal to}20 times greater than that of C4-bp on a weight basis. In relation to cell-bound C3b, the differences in activity were even more marked. Whereas beta1H enhanced the effects of C3bINA on the erythrocyte intermediate EC3b, inhibiting the assembly of EC3bBb, C4-bp was without effect even at concentrations {approximately equal to}300 times greater than beta1H. Therefore, under physiological conditions, it is likely that beta1H is the key protein which controls the function of C3b, and that C4-bp activity is directed mainly toward the cleavage of C4b. We also examined the relation between C4-bp and the C3b-C4bINA cofactor described by Stroud and collaborators (3, 4). By functional, physico-chemical and immunological criteria, they are the same protein.
C'3 phenotype and gene frequencies observed in two Italian samples are reported. The allele frequencies resemble those reported for other Caucasian populations. Five different rare variants are described.