Monoclonal Antibody‐Mediated, Complement‐Independent Binding of Human Tumor Necrosis Factor‐α to Primate Erythrocytes via Complement Receptor 1

Monoclonal antibody (MAb)-based heteropolymers (HP) were used to simulate immune adherence. The HP is constructed by cross-linking MAbs that recognize complement receptor 1 (CR1) and tumor necrosis factor-alpha (TNF-alpha). 125I-labeled TNF-alpha was cocultured with either sheep, monkey, or human erythrocytes in the presence or absence of HP. Human erythrocytes demonstrated 63% +/- 0 (mean +/- SD) binding of 125I-labeled TNF-alpha, while binding of 125I-labeled TNF-alpha in the absence of HP was 4% +/- 1% (P < .001). Monkey erythrocytes showed similar results, while sheep erythrocytes (which lack CR1) demonstrated low binding. The effect of HP binding on biologic activity of TNF-alpha was examined in an assay of stimulated human neutrophils. The HP completely inhibited the ability of TNF-alpha to prime neutrophils, occurring regardless of the presence or absence of erythrocytes but solely dependent on the addition of HP. Thus, the HP facilitated specific, saturable, and significant binding of 125I-labeled TNF-alpha to primate erythrocytes in vitro.