Ig molecules are highly modular proteins, in which the variable and constant domains have clear, conserved sequence patterns.
[2][3] Immunoglobulin-like domains that are related in both sequence and structure can be found in several diverse protein families.
Ig-like domains are involved in a variety of functions, including cell–cell recognition, cell-surface receptors, muscle structure and the immune system.
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.