Affinity of fibronectin for polyclonal IgG.

Fibronectin (Fn) is an adhesive glycoprotein that plays an important role in reticuloendothelial system functioning. Fn binds several macromolecules, it is found in cryoprecipitates obtained from patients with different diseases and it interacts in vitro with immune complexes. The interaction between Fn and polyclonal IgG was characterized by ligand affinity chromatography. After IgG was modified by attachment to a solid matrix or heat aggregation, it was able to interact with either soluble or immobilized Fn. The binding was highly influenced by ionic strength and pH. The estimated affinity constants were 3.0 x 10(6)/M when soluble Fn was applied to solid phase IgG and 2.3 x 10(7)/M when aggregated IgG interacted with immobilized Fn. The interaction may be relevant in situations in which immune complexes are involved.