CD3D

CD3D is a human gene that encodes the delta chain of the CD3 complex, a component of the T-cell receptor (TCR) signaling apparatus. The protein product, CD3 delta, is a transmembrane glycoprotein that associates with other CD3 chains (CD3E and CD3G) and the zeta chains to form the CD3-TCR complex on the surface of T lymphocytes.

Function: The CD3 complex participates in TCR assembly and signal transduction. Upon engagement of the TCR with peptide-MHC, ITAM-containing cytoplasmic tails transduce signals that drive T cell activation, differentiation, and proliferation. CD3D contributes to complex stability and proper surface expression of the TCR-CD3 complex.

Genetics and expression: The CD3D gene is located on chromosome 11 in humans and is expressed mainly in developing thymocytes and mature T cells, with expression levels varying by T cell subset and activation state.

Clinical relevance: Alterations in CD3D function can disrupt T cell development and signaling, and rare mutations have been associated with immunodeficiency disorders characterized by reduced T cell numbers and impaired immune responses. CD3D is also used in research as a marker of T cell lineage and as part of multicolor immunophenotyping panels.

Evolution and model organisms: CD3D is conserved across jawed vertebrates, with orthologs in mice and other mammals that play similar roles in TCR signaling.