Reactivity of human C-reactive protein with positively charged liposomes.

Interaction of CRP with liposomes was studied by agglutination, complement consumption, and the binding assay. Liposomes composed of phosphatidylcholine and stearylamine were agglutinated with CRP. The interaction of CRP and liposomes was further demonstrated by the consumption of hemolytic complement activity. Stearylamine could be substituted by cetyltrimethylammonium bromide, indicating that positively charged molecules were required for the interaction. Agglutination of liposomes caused by CRP was dependent on the fatty acid composition of phosphatidylcholine, cholesterol content and temperature. Differential scanning calorimetry measurement revealed that both the agglutination of liposomes and the consumption of complement caused by CRP required the fluid state of membranes. Particle electrophoresis measurement showed that stearylamine in fluid state membranes was more dispersed than in rigid state membranes indicating that lateral distribution of stearylamine affected the reactivity of liposomes. The mode of complement activation by the interaction of CRP with positively charged liposomes was similar to that observed in the system of protamine and heparin.