Relevance of the low-affinity type of the Fcγ-receptor IIIa-polymorphism in bullous pemphigoid

Bullous pemphigoid (BP) is mediated by autoantibodies directed against molecules of the basement membrane zone. The biological function of antibodies involves binding to Fc-receptors expressed on human leucocytes. Recent studies suggested that a functional single-nucleotide-polymorphism of the Fcγ-receptor IIIa (FcγRIIIa = CD16) at nucleotide 559 might predispose to the development of antibody-associated autoimmune disorders. This allelic difference affects the level of receptor affinity by predicting either a phenylalanine (F 158, low-affinity) or valine (V 158, high-affinity). We investigated if inherited frequencies of the high- and low-affinity FcγRIIIa polymorphism differed between patients with BP and healthy subjects. Genomic DNA from peripheral white blood cells was analyzed regarding FcγRIIIa polymorphism at nucleotide 559 by an established polymerase chain reaction. Sixty-seven Caucasian patients with BP and 88 healthy controls were included into the study. There was no significant difference in the distribution of the homozygous high-affinity FcγRIIIa-allotype (V/V) between BP-patients (14.9%) and healthy control subjects (20.5%). In contrast, 58.2% of the BP-patients were homozygous for the low-affinity FcγRIIIa-allotype (F/F), compared to 28.4% of the healthy controls (P = 0.001, OR 3.51). The frequencies of the polymorphism in the control group were in range of formerly published frequencies for healthy Caucasian subjects. Thus, the FcγRIIIa (158 F/V) polymorphism may modulate the susceptibility to acquire BP.