Most hematopoietic cells express a wide variety of receptors for tbe Fc portion of immunoglobulins (FcR) belonging to the immun‐noreceptor family. FcRs are multichain complexes composed of ligand‐binding a chains, which determine Ig binding, and signal tranduction subunits, bearing a conserved immunoreceptor tyrosine‐based activation motif (ITAM). Besides signaling, most FcyRs also efficiently internalize antigen‐antibodies complexes and thus induce efficient processing of antigens into peptides presented by major histocompatibility complex (MHC) class II molecules. Importantly, ITAMs and cyiosolic effectors of cell signaling also determine FcyR's endocytic transport and antigen presentation capacities.