Association of IgG1 Antibody Clearance with FcγRIIA Polymorphism and Platelet Count in Infliximab-Treated Patients

The FcγRIIA/CD32A is mainly expressed on platelets, myeloid and several endothelial cells. Its affinity considered insufficient for allowing significant binding of monomeric IgG, while its H131R polymorphism (histidine > arginine at position 131) influences multimeric IgG2. Platelet FcγRIIA has been reported to contribute IgG-containing immune-complexe clearance. Given our finding that platelet actually binds we investigated the role platelets in IgG antibody elimination. We used pharmacokinetics analysis infliximab (IgG1) individuals with controlled Crohn’s disease. influence count was quantified by multivariate linear modelling. half-life increased R allele number (13.2, 14.4 15.6 days HH, HR RR patients, respectively). It decreased increasing carriers: from ≈20 (RR) ≈17 (HR) 150 × 109/L, respectively, ≈13 (both RR) 350 109/L. Moreover, a flow cytometry assay showed IgG1 bound efficiently H allotypes, whereas panitumumab IgG2 poorly latter. propose (and presumably any antibody) elimination partly due an unappreciated mechanism dependent FcγRIIA, which probably tuned