Table 1.

Summary of roles of CCR7

Role in the immune system	Mechanism	References
Thymic architecture and function	CCR7 is involved in the recruitment of fetal hematopoietic progenitors and coordination of migratory events of thymocytes at their different maturation and selection ages in the thymus	[11,12,19-21]
Regulatory T-cell function	CCR7 is required for Treg cell homing and positioning within the paracortical LN area. Treg function is impaired in CCR7-deficient mice	[15-17]
T-cell priming	Age-experienced DCs (entering via afferent lymphatics) and T cells (via HEVs) use CCL21-coated stromal networks in the T-cell zone to interact with each other and generate the effector T-cell pool	[6,7,22,23]
Lymphocyte recirculation in peripheral tissues	CCR7 and CCL21 contribute to T-cell recruitment and egress from peripheral tissues, and the pleural and the peritoneal cavities	[24-28]
Peripheral tissue- resident DC trafficking	Tolerogenic (homeostatic) DCs and inflammation-induced DCs acquire CCR7 expression as they exit from peripheral tissues to present antigens in the draining LN	[3,14,29,30]
DC survival, maturation and antigen uptake	CCR7-mediated signaling positively regulates the survival and rate of endocytosis of the mature DCs. CCR7 also induces dendritic cytoplasmic extensions that may contribute to the ability of DCs to present antigens	[31-33]
T-cell homeostasis	CCR7 ligands support the survival and homeostatic expansion of naive T cells	[18,34]
B-cell help	CCR7 upregulation mobilizes follicular B cells towards the T-cell zone in the LN to receive ‘help’ from CD4+ T helper cells	[35,36]

CCR7 C-C chemokine receptor 7; DC dendritic cell; HEV high endothelial vessel; LN LN.