Test Details: CD2 (cluster of differentiation 2) is a cell adhesion molecule found on the surface of T cells and natural killer (NK) cells. In addition to its adhesive properties, CD2 also acts as a co-stimulatory molecule on T and NK cells. CD2 is a specific marker for T cells and NK cells, and can therefore be used in immunohistochemistry to identify the presence of such cells in tissue sections. The great majority of T cell lymphomas and leukaemias also express CD2, making it possible to use the presence of the antigen to distinguish these conditions from B cell neoplasms.