|Detection of FCRL1/FcRH1 in Mouse Splenocytes by Flow Cytometry. Mouse splenocytes were stained with Rat Anti-Mouse B220/CD45R PE‑conjugated Monoclonal Antibody (Catalog # FAB1217P) and either (A) Rat Anti-Mouse FCRL1/FcRH1 APC‑conjugated Monoclonal Antibody (Catalog # FAB7286A) or (B) Rat IgG1 Allophycocyanin Isotype Control (Catalog # IC005A). View our protocol for Staining Membrane-associated Proteins.|
FCRL1 (Fc Receptor-Like Protein 1), also known as CD307a, FcRH1 and IFGP1, is a 36 kDa (predicted) member of the Ig Superfamily. In mouse, it is found on mature follicular and marginal B cells, splenic T cells and NK cells. It would appear that mouse FCRL1 serves as an inhibiting coreceptor, in as much as it contains a series of cytoplasmic ITIM motifs. Mature mouse FCRL1 is a 327 amino acid (aa) type I transmembrane protein (aa 17-343). It contains a 203 aa extracellular region (aa 17‑219) that shows two C2-type Ig-like domains (aa 17-200), and a 103 aa cytoplasmic domain. There are multiple potential splice variants. One shows a deletion of aa 206-248 (potentially soluble), a second contains a six aa substitution for aa 319-343, a third possesses a three aa substitution for aa 209-343, and a fourth shows a 21 aa substitution for Ala11. Over aa 17-219, mouse FCRL1 shares 83% aa sequence identity with rat FCRL1. Over the same region, it shares 63% aa sequence identity with human FCRL1 when a third Ig-like domain that is present in human is excluded from the analysis.