 C2-set domains, which are Ig-like domains resembling the antibody constant domain.C2-set domains are found primarily in the mammalian T-cell surface antigens CD2 (Cluster of Differentiation 2), CD4 and CD80, as well as in vascular (VCAM) and intercellular (ICAM) cell adhesion molecules.CD2 mediates T-cell adhesion via its ectodomain, and signal transduction utilising its 117-amino acid cytoplasmic tail.