Semaphorin-4D/CD100 (E5C3B) XP^® Rabbit mAb #53108

Semaphorin-4D/CD100 (Sema4D) is a disulfide-linked homodimeric type 1 transmembrane glycoprotein belonging to the class IV family of membrane bound semaphorins. The extracellular domain of Sema4D contains a cysteine-rich semaphorin-like domain, an Ig-like domain, and a PSI domain (1). Research studies have suggested that the cytoplasmic domain has a signaling function as it is phosphorylated on serine residues (2). Initial studies involving Sema4D revealed that it was implicated in axon guidance within the central nervous system through binding its high affinity receptor, plexin-B1 (3). Sema4D function has also been extensively characterized in the immune system and is the first semaphorin found to be expressed on the surface of many types of immune cells (4-6). In the immune system, CD72 serves as a low-affinity receptor for Sema4D (7) and research studies have shown that Sema4D not only regulates T-cell activation (8,9) but is also involved in the regulation of B-cell survival and differentiation (5). Many of the physiologic effects of Sema4D in the immune system are regulated by a soluble extracellular domain-containing fragment generated through proteolytic cleavage (10).

Sema4D has also been implicated in oncogenesis as research studies have demonstrated overexpression in multiple types of solid tumors (11,12). The role of Sema4D in oncogenesis, in part, has been linked to its ability to promote tumor angiogenesis (13), cell invasion (14), and immunosuppression through enhancement of myeloid derived suppressor cell function (15).