T-cell surface antigen CD2 (CD2) is a T-cell specific surface glycoprotein that is critically important for mediating adherence of T cells to antigen-presenting cells or target cells. It interacts with lymphocyte function-associated antigen (LFA-3) and CD48/BCM1 to mediate adhesion between T cells and other cell types. CD2 is involved in triggering T cells, and the cytoplasmic domain is involved in signaling. CD2 is a pan T-cell marker. CD2 antibody labels T-cell, thymocytes and natural killer (NK) cells. CD2 is absent in a small subset of T cells. CD2 antibody is useful for identification of precursor and mature T-cell lymphomas. Aberrant loss of CD2 in T-cell lymphomas may help to distinguish them from reactive T-cell proliferations.