Complement activation by IgG immobilized on methylated silicon.

Activation of the complement system by immobilized IgG on methylated silicon was studied by ellipsometry/antibody-, ELISA-, and RIA techniques after exposure to human serum at 37 degrees C for up to 1 h. The IgG-covered surfaces rapidly activated the complement system and the combined results suggest an initial classical pathway activation. Complement factor 1q (C1q) and IgG were antibody-detectable on the surfaces for serum incubations up to 5 min but not thereafter. Anti-C3c and anti-properdin bound to the surfaces at all serum incubation times. Experiments with 125I-IgG preadsorbed to surfaces, or added to normal-, EGTA-, and EDTA-sera, showed that IgG was not displaced from the protein film by serum.