Characterization of human Fcrl4-positive B cells

FCRL4 is an immunoregulatory receptor that belongs to the Fc receptor-like (FCRL) family. In healthy individuals, this protein is specifically expressed by memory B cells (MBCs) and is preferentially localized in subephitelial regions of lymphoid tissues. An expansion of FCRL4+ B cells has been shown in blood or other tissues in various infectious or autoimmune pathologies. In the present work, we generated and characterized in vitro FCRL4+ B cells from purified MBCs using T-dependent and/or T-independent stimulation. FCRL4+ B cells account for 17% of cells generated at day-4 of culture. Transcriptomic and phenotypic analysis of FCRL4+ cells show that they are closely related to FCRL4+ tonsillar MBCs. Interestingly, these cells highly express inhibitory receptors genes as described for exhausted FCRL4+ MBCs in the blood of HIV-viremic individuals. In agreement, in vitro generated FCRL4+ B cells show a significant underexpression of cell cycle genes with a two fold weaker number of cell division compared to FCRL4- cells. Finally, resulting from their reduced proliferation and differentiation potential, we show that FCRL4+ cells are not prone to generate plasma cells, contrary to FCRL4- cells. Given the difficulty to access to in vivo FCRL4+ cells, our in vitro model could be of major interest to study the biology of normal and pathological FCRL4+ cells. Gene expression profiling of human FCRL4 negative cells and FCRL4 positive cells generated in vitro from purified blood memory B cells.