Inhibitory receptor that acts as a critical regulator of hematopoietic lineage differentiation, megakaryocyte function and platelet production (PubMed:12665801, PubMed:17311996, PubMed:27743390). Inhibits platelet aggregation and activation by agonists such as ADP and collagen-related peptide (PubMed:12665801). This regulation of megakaryocate function as well as platelet production ann activation is done through the inhibition (via the 2 ITIM motifs) of the receptors CLEC1B and GP6:FcRgamma signaling (PubMed:17311996). Appears to operate in a calcium-independent manner (PubMed:12665801). {ECO:0000269|PubMed:12665801, ECO:0000269|PubMed:17311996, ECO:0000269|PubMed:27743390}. Isoform B, displayed in this entry, is the only isoform to contain both a transmembrane region and 2 immunoreceptor tyrosine-based inhibitor motifs (ITIMs) and, thus, the only one which probably has a role of inhibitory receptor. Isoform A may be the activating counterpart of isoform B. . This is the function of MPIG6B (megakaryocyte and platelet inhibitory receptor G6b, ENSG00000204420).