CD19

CD19 is a type of protein that in humans is encoded by the CD19 gene. It is a member of the immunoglobulin superfamily and has two immunoglobulin (Ig) domains. The CD19 protein is expressed on the surface of B cells, a type of white blood cell.

Structure

The CD19 protein is a 95 kDa transmembrane glycoprotein that consists of 556 amino acids. It has a large extracellular domain that contains two Ig domains, and a small cytoplasmic domain that contains multiple phosphorylation sites.

Function

CD19 plays a crucial role in establishing intrinsic B cell signaling thresholds through modulating both B cell receptor (BCR)-dependent and independent signaling. It works in conjunction with CD21, CD81, and CD225 in the B cell co-receptor complex. The extracellular domain of CD19 interacts with the B cell receptor, while the cytoplasmic domain interacts with signaling molecules such as phosphatidylinositol 3-kinase (PI3K) and Lyn kinase.

Clinical significance

Alterations in CD19 expression levels or mutations in its gene have been implicated in various diseases. For instance, CD19 is often overexpressed in B cell lymphoma and leukemia, and is a target for various immunotherapies including CAR-T cell therapy. In contrast, CD19 deficiency is associated with hypogammaglobulinemia, a condition characterized by low levels of immunoglobulins and increased susceptibility to infections.

See also

• Cluster of differentiation
• B cell receptor
• Immunoglobulin superfamily