CD2 is a 50kD type I transmembrane glycoprotein and a member of the immunoglobulin superfamily. It is a specific marker for T lymphocytes, natural killer cells, thymic B cell subsets, and some antigen presenting cells. CD2 interacts with CD58 (LFA-3) and CD48 to mediate cell adhesion and induce co-stimulatory signals in T lymphocytes.