Fc receptor-like 5 (FCRL5)

Fc receptor-like 5 (FCRL5) is a single-pass type I membrane receptor predominantly expressed in B cells, with high expression in plasma cells and in malignancies such as multiple myeloma[1][4]. It is a member of the immunoglobulin receptor superfamily and contains multiple immunoglobulin-like domains. Unlike classical Fc receptors, FCRL5 binds intact immunoglobulin G (IgG), allowing B cells to "sense" antibody quality, possibly influencing immune complex responses[2][6][9]. By engaging immunoreceptor tyrosine-based inhibitory motifs (ITIMs) and ITAM-like sequences, FCRL5 can finely tune B-cell receptor (BCR) signaling, acting as both a negative and positive coreceptor[1][8]. FCRL5 is implicated in immune regulation and is upregulated in certain cancers and autoimmune conditions, making it a promising, although not yet fully validated, therapeutic target for antibody- and cellular-based immunotherapies[4][7].

Other names

Fc receptor-like protein 5CD307Immunoglobulin superfamily receptor translocation-associated 2 (IRTA2)CD307e

Modulation of B-cell activity through co-inhibitory or co-stimulatory signaling via ITIM and ITAM-like motifs CAR-T cell therapy: FCRL5-directed CAR-T cells bind and lyse malignant plasma cells in multiple myeloma, leading to immune-mediated tumor cell death[4].