At least five CD1 genes (CD1a, b, c, d and e) have been identified. CD1, cortical thymocytes, Langerhans cells and It is expressed on dendritic cells. Absent in mature peripheral blood T cells, but activated Intracytoplasmic expression is detected in T lymphocytes. CD1 proteins, non-peptide lipid and glycolipid It has been shown to restrict the T-cell response to antigens and play a role in non-classical antigen presentation.