FCRL2 is a transmembrane receptor belonging to the Fc receptor-like family with regulatory roles in B cell biology and immune function. Structurally, FCRL2 contains three immunoglobulin-like domains and a C-terminal mucin-like domain with conserved dileucine signals 1. The protein functions as a bidirectional signaling regulator, possessing both immunoreceptor tyrosine-based activation motifs (ITAM) and inhibitory motifs (ITIM) 2. Engagement of FCRL2 by monoclonal antibodies inhibits B cell receptor-mediated signaling through suppression of calcium mobilization and phosphorylation of mitogen-activated protein kinases 2. In chr1 lymphocytic leukemia (CLL), FCRL2 expression shows 94.4% concordance with IGHV mutation status, exceeding CD38 and ZAP-70, and predicts time to first therapy with superior prognostic value 3. In IgA nephropathy, FCRL2 is significantly downregulated in patients and correlates with glycosylation-related gene expression 4. Mendelian randomization analysis identified FCRL2 as a causal protein associated with IgA nephropathy across multiple ancestry populations 5. In rheumatoid arthritis, FCRL2 expression correlates with inflammatory markers, disease activity score, and anti-cyclic citrullinated peptide antibody levels 6. Preliminary evidence suggests FCRL2 involvement in major depression treatment response mechanisms 7.