Semaphorin-4D also known as Cluster of Differentiation 100 (CD100), is a protein

Protein

Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

 of the semaphorin

Semaphorin

Semaphorins are a class of secreted and membrane proteins that act as axonal growth cone guidance molecules. They primarily act as short-range inhibitory signals and signal through multimeric receptor complexes. They are usually cues to deflect axons from inappropriate regions, especially...

 family that in humans is encoded by the SEMA4D gene

Gene

A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

.

Function

Semaphorin 4D (Sema 4D) is an axon guidance

Axon guidance

Axon guidance is a subfield of neural development concerning the process by which neurons send out axons to reach the correct targets...

 molecule which is secreted by oligodendrocyte

Oligodendrocyte

Oligodendrocytes , or oligodendroglia , are a type of brain cell. They are a variety of neuroglia. Their main function is the insulation of axons in the central nervous system of some vertebrates...

s and induces growth cone

Growth cone

A growth cone is a dynamic, actin-supported extension of a developing axon seeking its synaptic target. Their existence was originally proposed by Spanish histologist Santiago Ramón y Cajal based upon stationary images he observed under the microscope...

 collapse in the central nervous system

Central nervous system

The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...

. By binding plexin B1 receptor

PLXNB1

Plexin B1 is a protein of the plexin family that in humans is encoded by the PLXNB1 gene.-Interactions:PLXNB1 has been shown to interact with ARHGEF12, Rnd1 and ARHGEF11.-Further reading:...

 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, CD100 binds CD72

CD72

CD72 , also known in murine biology as Lyb-2, is a protein active in the immune system of animals. It consists of two identical halves, each of about 39-43 daltons, and is a C-type lectin. Its primarily locus of expression is B-cells, where it appears to mediate aspects of B-cell - T-cell...

 to activate B cell

B cell

B cells are lymphocytes that play a large role in the humoral immune response . The principal functions of B cells are to make antibodies against antigens, perform the role of antigen-presenting cells and eventually develop into memory B cells after activation by antigen interaction...

s and dendritic cell

Dendritic cell

Dendritic cells are immune cells forming part of the mammalian immune system. Their main function is to process antigen material and present it on the surface to other cells of the immune system. That is, dendritic cells function as antigen-presenting cells...

s, though much about this interaction is still under investigation.

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