EFFECT OF COMPLEMENT ON THE RHEOLOGICAL PROPERTIES OF THE ERYTHROCYTE-MEMBRANE

The effect of complement (C) on the erythrocyte deformability was inve stigated. Sheep erythrocytes (E) were sensitized with specific antibod ies (A) and treated with various doses of human C. Gravity filtration of unlysed EAC showed a C dose-dependent decrease in whole cell deform ability, which was shown to be due to an impairment of the membrane rh eological properties. As the fluidity of the lipid bilayer, sensed by a spin label, was not modified, the observed effects should be related to an interaction between C and the cytoskeleton. The influence of C3 b and C3d in these processes seems unlikely, as similar hemagglutinati on titers were found, respectively, for anti-C3c and anti-C3d antisera against the varying EAC. The study of the degree of spontaneous hemol ysis of EAC in buffers with solutes of different Stokes radii showed t hat differing-sized functional C lesions were produced, and that the f ormation of larger-sized lesions was favored by incubation with higher C doses. These results suggest that the insertion of proteins from th e membrane attack complex, C5b-9 (MAC), into the erythrocyte membrane may be responsible for the effect of C on the rheological properties o f the erythrocyte membrane.