Mouse FCRL1/FcRH1 Antibody

FCRL1 (Fc receptor-like protein 1; also 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. FCRL1 is likely not a receptor for immunoglobulin. At present, 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.