CD103/Integrin alpha E is a new member of the integrin series of adhesion molecules containing the beta7 subunit. This antigen defines a developmentally important subset of T cells, namely mucosal T cells including all IEL (intraepithelial lymphocytes) and ~20% of lamina propria T cells. Expression of CD103 is more restricted outside these mucosal organs, appearing at lower levels on T cell subsets of the lymph node, dendritic epidermis and periphery. In non-epithelial CD103+ T cells there is a bias toward expression on CD8+ cells. Integrin alpha E is a heterodimer comprising a 150kDa alpha chain and a 120kDa beta chain. Integrin alpha E is expressed by approximately 1% of peripheral blood lymphocytes, activated T lymphocytes and by hairy cell leukaemia cells. The antigen is also expressed by intraepithelial lymphocytes.
