Binds to the Fc region of immunoglobulins gamma. Low affinity receptor. Interacts with FGR and LYN. Macrophages and polymorphonuclear leukocytes express preferentially isoform 2R-B1. B-lymphocytes express isoform 2R-B1, isoform 2R-B2 and isoform 2R-B3. Contains 1 copy of a cytoplasmic motif that is referred to as the immunoreceptor tyrosine-based inhibitor motif (ITIM). This motif is involved in modulation of cellular responses. The phosphorylated ITIM motif can bind the SH2 domain of several SH2-containing phosphatases. Phosphorylated by SRC-type Tyr-kinases such as LYN, BLK, FYN and SYK.