CD2 and the regulation of T cell anergy

Many of the properties of CD2, a cell-surface glycoprotein expressed by T lymphocytes, suggest that it plays an important role in regulating T cell responses. For example, CD2 is both physically and functionally associated with TCR, and, depending on the mode of its ligation, can deliver either stimulatory or inhibitory signals to T cells. Nevertheless, it has been difficult to define clearly a unique role for CD2 in T cell biology, a problem brought to the fore by the targeted disruption of the murine CD2 gene, which results in a healthy mouse with an apparently normal immune system.