FCRL5, also known as CD307 or IRTA2, is a surface protein expressed selectively on B cells and plasma cells . This protein has both an immunoreceptor tyrosine-based activation motif (ITAM)-like sequence and two consensus immunoreceptor tyrosine-based inhibitory motifs (ITIM) in its cytoplasmic region . FCRL5 is implicated in B cell development and lymphomagenesis . It may have an immunoregulatory role in marginal zone B-cells.