Search

The complement-fixing capacity of aggregated immunoglobulins with varying molecular weights has been explored. It has been demonstrated that as the molecular weight of a complex rises, the complement-fixing capacity increases. The amount of unfixed complement depends nonlinearly on the concentration of complement added and aggregated complexes in solution. The size of the complexes rather than their concentration plays the key role in the measurement of the complement-fixing capacity of aggregated immunoglobulins.

The authors studied and compared the complement-fixing activity of model immune complexes with different molecular mass. The complement-fixing activity of the complexes was found to be linearly independent of the molecular mass, being mainly determined by the size of the complex, and to be slightly dependent on the concentration of aggregated immunoglobulins. As far as the aggregates with a molecular mass over 20 IgG are concerned, addition of complement leads to the dissociation of the complexes.

The mechanism of complement complexing with immunoglobulins in the solution has been shown to depend on the nature and structure of the reagents. The maximum complexing rate can be recorded during interaction of the native complement with aggregated antibodies. The complexing rate varies with the complement type. Guinea pig fresh serum is the most active in this respect.