http://www.creativebiomart.net/description_382907_12.htm

Semaphorin-4D, also known as SEMA4D and CD100, is a single-pass type I membrane protein which belongs to the semaphorin family. Semaphorin-4D / SEMA4D contains one Ig-like C2-type (immunoglobulin-like) domain, one PSI domain and one Sema domain. Semaphorin-4D / SEMA4D is strongly expressed in skeletal muscle, peripheral blood lymphocytes, spleen, and thymus and also expressed at lower levels in testes, brain, kidney, small intestine, prostate, heart, placenta, lung and pancreas, but not in colon and liver. Semaphorin-4D / SEMA4D may play a functional role in the immune system, as well as in the nervous system. Induces B-cells to aggregate and improves their viability. Semaphorin-4D / SEMA4D is an axon guidance molecule which is secreted by oligodendrocytes and induces growth cone collapse in the central nervous system. By binding plexin-B1 receptor it functions as an R-Ras GTPase-activating protein (GAP) and repels axon growth cones in both the mature central nervous system. In the immune system, Semaphorin-4D / SEMA4D binds CD72 to activate B cells and dendritic cells. It is involved in oligodendrogenesis during development and during recovery from ischemic injury.