<p>The CD2 adhesion molecule is a cell surface protein expressed by T cells and natural killer cells. CD2's extracellular domain contains immunoglobulin-like domains that are glycosylated at two sites and can mediate homodimerisation [<cite idref="PUB00034961"/>]. Ligation of CD2 by CD58 in humans or CD48 in mice helps T cells adhere to antigen-presenting cells, and initiates signal transduction pathways that enhance signalling through the T cell receptor for antigen. CD2 knockout mice exhibit essentially normal immune function [<cite idref="PUB00034962"/>], and it is thought that CD2 is somewhat functionally redundant with other T cell co-stimulatory receptors such as CD28 [<cite idref="PUB00034963"/>].</p> T-cell adhesion molecule CD2