Could the expression of CD86 and FcγRIIB on B cells be functionally related and involved in driving rheumatoid arthritis?

In a recent article Catalán and colleagues [1] examined the expression of FcγRIIB in na？ve, memory and plasmablast B cell subsets from peripheral blood of patients with rheumatoid arthritis (RA) and the results were correlated with levels of autoantibodies to cyclic citrullinated proteins (anti-CCP) detected in matching serum. Firstly, they observed reduced FcγRIIB expression in memory and plasmablast B cells from patients compared to the levels expressed on B cells from healthy controls. Secondly, the expression levels of FcγRIIB inversely correlated with the titre of anti-CCP antibodies in patients' serum. Indeed, RA patients with low autoantibody titres expressed higher levels of this receptor. Th irdly, they also report an increased frequency of CD86, usually up-regulated upon activation, on memory and na？ve B cells [2]. Intriguingly, RA patients responding to adalimumab treatment display 'normalized' levels of CD86 only on memory B cells, but not on na？ve B cells, and reduced expression of FcγRIIB only on na？ve B cells, but not on memory B cells, and this was accompanied by unchanged levels of anti-CCP antibodies. Although these results are based on a relatively small group of patients, they could, if confirmed, advocate the use of FcγRIIB expression coupled to anti-CCP responses as a predictive biomarker to monitor the early stage of disease and progression.Human Fc receptors for IgG (FcγRI, FcγRIIA, FcγRIIC, FcγRIIIA, FcγRIIIB, FcγRIIB) exert different functions and have diverse affinities for the Fc fragment of IgG, and these receptors are differentially expressed by a variety of cells [3]. B cells, however, exclusively express FcγRIIB, an inhibitory receptor that binds IgG immune complexes and negatively regulates B cell receptor activation. FcγRIIB is able to suppress or block B cell receptor activation by transmitting inhibitory signals via its cytoplasmic immunoreceptor tyrosine-based inhibitory (ITIM) motif upon simultaneous engagement with the B cell r