CD2, also known as T-cell surface antigen T11/Leu-5, is a cell adhesion molecule found on the surface of T cells and natural killer (NK) cells. It interacts with other adhesion molecules, such as lymphocyte function-associated antigen-3 (LFA-3/CD58) in humans, or CD48 in rodents, which are expressed on the surfaces of other 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. Recombinant human CD2 protein, fused to His-tag at N-terminus, was expressed in E.coli.