 The CD45 protein family consists of multiple members that are all products of a single complex gene.This gene contains 34 exons, producing a massive protein with extracellular and cytoplasmic domains that are both unusually large.Exons 4, 5, and 6 (corresponding to protein regions A, B, and C) are alternatively spliced to generate up to eight different protein products featuring combinations of zero, one, two, or all three exons.