CD44 & CD3

CD44 is a type I transmembrane protein and member of the cartilage link protein family. Several CD44 ligands have been identified. CD44 is a major cell surface receptor for hyaluronan, a component of the extracellular matrix, and it also interacts with osteopontin (OPN), collagen, and laminin.

The protein encoded by this gene is part of the T-cell receptor/CD3 complex (TCR/CD3 complex) and is involved in T-cell development and signal transduction. The encoded membrane protein represents the delta subunit of the CD3 complex, and along with four other CD3 subunits, binds either TCR alpha/beta or TCR gamma/delta to form the TCR/CD3 complex on the surface of T-cells. Defects in this gene are a cause of severe combined immunodeficiency autosomal recessive T-cell-negative/B-cell-positive/NK-cell-positive (SCIDBNK). Two transcript variants encoding different isoforms have been found for this gene. Other variants may also exist, but the full-length natures of their transcripts has yet to be defined.