Fc gamma RII alpha: sequencing of the ligand binding domain in systemic lupus erythematosus patients.

The receptor for the Fc portion of IgG (Fc gamma R) is involved in the slow clearance of immune complexes. To perform this role it must be cross-linked by IgG bound in its extracellular domains. It has been suggested that defective Fc gamma R-mediated clearance of immune complexes may play a role in the pathogenesis of autoimmune connective tissue disorders. We have sequenced DNA encoding the second extracellular domain of Fc gamma RII alpha in six patients with SLE, to investigate whether point mutations may be responsible for encoding a defect in the IgG binding capacity of the receptor. We were able to identify the point mutation which discriminates high and low responder genotypes but found no other change from the published DNA sequence for this region.