CD154

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CD40 ligand (TNF superfamily, member 5, hyper-IgM syndrome)
PDB rendering based on 1aly.
Available structures: 1aly, 1i9r
Identifiers
Symbol(s)	CD40LG; TRAP; CD154; CD40L; HIGM1; IGM; IMD3; T-BAM; TNFSF5; gp39; hCD40L
External IDs	OMIM: 300386 MGI: 88337 HomoloGene: 56
Gene ontology Molecular Function: • cytokine activity • tumor necrosis factor receptor binding • CD40 receptor binding Cellular Component: • extracellular space • soluble fraction • integral to plasma membrane • membrane Biological Process: • anti-apoptosis • inflammatory response • immune response • leukocyte adhesion • signal transduction • platelet activation • B cell proliferation • isotype switching • regulation of immunoglobulin secretion
RNA expression pattern
More reference expression data
Orthologs
	Human	Mouse
Entrez	959	21947
Ensembl	ENSG00000102245	ENSMUSG00000031132
Uniprot	P29965	Q0VEI3
Refseq	NM_000074 (mRNA) NP_000065 (protein)	NM_011616 (mRNA) NP_035746 (protein)
Location	Chr X: 135.56 - 135.57 Mb	Chr X: 53.56 - 53.57 Mb
Pubmed search	[1]	[2]

CD154, also called CD40 ligand or CD40L, is a protein that is primarily expressed on activated T cells and is a member of the TNF family of molecules. It binds to CD40 on antigen-presenting cells (APC), which leads to many effects depending on the target cell type. In general, CD40L plays the role of a costimulatory molecule and induces activation in APC in association with T cell receptor stimulation by MHC molecules on the APC. The protein encoded by this gene is expressed on the surface of T cells. It regulates B cell function by engaging CD40 on the B cell surface. A defect in this gene results in an inability to undergo immunoglobulin class switch and is associated with hyper-IgM syndrome.^[1]

[edit] Expression of CD154

CD40 ligand is primarily expressed on activated CD4+ T lymphocytes but is also found in a soluble form. While CD40L was originally described on T lymphocytes, its expression has since been found on a wide variety of cells, including platelets, mast cells, macrophages, basophils, NK cells, B lymphocytes, as well as non-haematopoietic cells (smooth muscle cells, endothelial cells, and epithelial cells)[3].

[edit] Specific effects on cells

[edit] Macrophages

In the macrophage, the primary signal for activation is IFN-γ from Th1 type CD4 T cells. The secondary signal is CD40L on the T cell, which binds CD40 on the macrophage cell surface. As a result, the macrophage expresses more CD40 and TNF receptors on its surface, which helps increase the level of activation. The activated macrophage can then destroy phagocytosed bacteria and produce more cytokines.

[edit] B cells

The B cell can present antigens to helper T cells. If the T cell recognizes the peptide presented by the B cell, the T cell synthesizes CD40L. The CD40L binds to the B cell's CD40 receptor, causing resting B cell activation. The T cell also produces IL-4, which directly binds to B cell receptors. As a result of this interaction, the B cell can undergo division, antibody isotype switching, and differentiation to plasma cells. The end-result is a B cell that is able to mass-produce specific antibodies against an antigenic target.

[edit] References

• Parham, Peter (2004). The Immune System, 2nd Ed, Garland Science, 169-173. ISBN 0-8153-4093-1. 

[edit] Further reading

[edit] External links

• MeSH CD154+Antigen

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