CD1 proteins have been demonstrated to restrict
T-cell response to non-peptide lipid and glycolipid
antigens. At least five CD1 genes (CD1a, b, c, d,
and e) have been identified. CD1a belongs to a
family of glycoproteins expressed on the surface
of various human antigen-presenting cells. In
particular, CD1a is a protein of 43 to 49 kDa, and
has been shown to be expressed on dendritic cells
and cortical thymocytes. Langerhans cells in the
skin and some epithelia also express this protein.
This antigen is expressed in cells comprising
Langerhans Cell Histiocytosis and Langerhans
Cell Sarcoma.
Anti-CD1a has been used to differentiate
various cutaneous Lymphomas (T-cell) from B-cell
Lymphomas and Pseudolymphomas. CD1a is also
expressed by some malignancies of T-cell lineage
and in Histiocytosis X.