Preparation of covalent IgG complexes of defined size and their clearance from the circulation of mice.

Covalent complexes of various sizes were made by coupling the photosensitive hapten, NAP (4-azido-2-nitrophenyl), to rabbit IgG and reacting the conjugates with rabbit anti-NAP antibodies. The resultant oligomers were stable, being eluted as the same discrete peaks after chromatography on gels both before and after injection into mice. Tests of their biological properties showed they fixed guinea pig complement in vitro in a size-dependent manner. Normal mice and mice with chronic endogenous circulating complexes cleared the oligomers according to size in a manner best described by a two-component exponential curve. There was no difference in the clearance rates between the two groups of mice. The advantages of these model complexes for examining the effect of circulating complexes on the mononuclear phagocyte system are discussed.