CCR7 regulates lymphocyte egress and recirculation through body cavities

T and B lymphocytes recirculate among blood, lymph, and extralymphoid tissues to ensure immune surveil-lance and the establishment of self-tolerance. The un-derlying mechanisms regulating homeostatic lympho-cyte recirculation through body cavities are not fully un-derstood. Here, we demonstrate that the homeostatic chemokine receptor CCR7 regulates homeostatic recir-culation of lymphocytes through body cavities. CCR7 deficiency results in massive accumulation of CD4 and CD8 T cells and B-2 B cells in the peritoneal and pleu-ral cavities. The increase in B-2 B and T lymphocytes is not associated with an altered maturation and/or acti-vation status of these cells. Mechanistically, an in-crease in peritoneal lymphocyte numbers is caused by impaired egress of CCR7-deficient lymphocytes from body cavities. These results establish that CCR7 plays a crucial role in lymphocyte exit from the PerC. J. Leu-koc. Biol. 87: 000–000; 2010