CD19

CD19 molecule
Identifiers
Symbols	CD19 ; B4; CVID3
External IDs	OMIM: 107265 MGI: 88319 HomoloGene: 1341 GeneCards: CD19 Gene
Gene ontology Molecular function • receptor signaling protein activity • protein binding Cellular component • intracellular • plasma membrane • integral component of plasma membrane • external side of plasma membrane • protein complex • extracellular exosome Biological process • cellular defense response • cell surface receptor signaling pathway • epidermal growth factor receptor signaling pathway • fibroblast growth factor receptor signaling pathway • Fc-epsilon receptor signaling pathway • innate immune response • neurotrophin TRK receptor signaling pathway • phosphatidylinositol-mediated signaling • regulation of immune response • B cell receptor signaling pathway • positive regulation of release of sequestered calcium ion into cytosol Sources: Amigo / QuickGO
RNA expression pattern
More reference expression data
Orthologs
Species	Human	Mouse
Entrez	930	12478
Ensembl	ENSG00000177455	ENSMUSG00000030724
UniProt	P15391	P25918
RefSeq (mRNA)	NM_001178098	NM_009844
RefSeq (protein)	NP_001171569	NP_033974
Location (UCSC)	Chr 16: 28.93 – 28.94 Mb	Chr 7: 126.41 – 126.41 Mb
PubMed search	[1]	[2]

B-lymphocyte antigen CD19, also known as CD19 (Cluster of Differentiation 19), is a protein that in humans is encoded by the CD19 gene. It is found on the surface of B-cells, a type of white blood cell.

Function

Lymphocytes proliferate and differentiate in response to various concentrations of different antigens. The ability of the B cell to respond in a specific, yet sensitive manner to the various antigens is achieved with the use of low-affinity antigen receptors. The CD19 gene encodes a cell surface molecule that assembles with the antigen receptor of B lymphocytes in order to decrease the threshold for antigen receptor-dependent stimulation.

CD19 is expressed on follicular dendritic cells and B cells. In fact, it is present on B cells from earliest recognizable B-lineage cells during development to B-cell blasts but is lost on maturation to plasma cells. It primarily acts as a B cell co-receptor in conjunction with CD21 and CD81. Upon activation, the cytoplasmic tail of CD19 becomes phosphorylated, which leads to binding by Src-family kinases and recruitment of PI-3 kinase.

As on T cells, several surface molecules form the antigen receptor and form a complex on B lymphocytes. The (almost) B cell-specific CD19 phosphoglycoprotein is one of these molecules. The others are CD21 and CD81. These surface immunoglobulin (sIg)-associated molecules facilitate signal transduction. On living B cells, anti-immunoglobulin antibody mimicking exogenous antigen causes CD19 to bind to sIg and internalize with it. The reverse process has not been demonstrated, suggesting that formation of this receptor complex is antigen-induced. This molecular association has been confirmed by chemical studies.

Interactions

CD19 has been shown to interact with:

• CD81,
• CD82
• Complement receptor 2, and
• VAV2.

In disease

Mutations in CD19 are associated with severe immunodeficiency syndromes characterized by diminished antibody production.

Since CD19 is a hallmark of B-cells, the protein has been used to diagnose cancers that arise from this type of cell - notably B-cell lymphomas. Since 2011 treatments targeting CD19 have begun to enter trials. Most current experimental anti-CD19 drugs in development work by exploiting the presence of CD19 to direct treatment specifically towards B-cell cancers. However, it is now emerging that the protein plays an active role in driving the growth of these cancers, most intriguingly by stabilizing the concentrations of the MYC oncoprotein. This suggests that CD19 and its downstream signaling may be a more attractive therapeutic target than suspected

CD19 has also been implicated in autoimmune diseases and may be a useful treatment target.

External links

• Mouse CD Antigen Chart
• Human CD Antigen Chart

This article incorporates text from the United States National Library of Medicine, which is in the public domain.