Role of DAP12 in innate and adaptive immune responses

DAP12 is a novel immunoreceptor tyrosine-based activation motifs (ITAM)-bearing transmembrane adapter molecule. This molecule, together with its partner receptor complex molecules including the killer cell activating receptors (KARs), myeloid DAP12 associating lectin-1 (MDL-1), triggering receptor expressed on myeloid cells 1/2/3 (TREM-1, TREM-2, TREM-3), and signal regulatory protein beta1 (SIRPbeta1), are expressed on the surface of NK and myeloid cells including antigen presenting cells. While the function of DAP12 and its associating molecules has just begun to be unveiled, emerging evidence suggests that these molecules play an important role in both innate and adaptive immune responses. In this review, we intend to provide an overview on what have been known and are still unknown to date about the function of these molecules based on the observations made by us and others.