Normal mouse kidneys contain activated and CD3⁺CD4 ^-CD8^- double-negative T lymphocytes with a distinct TCR repertoire

Healthy liver, intestine, lung, and skin harbor resident lymphocytes with conventional and unconventional phenotypes. Lymphocytes also have been detected in healthy mice kidneys; however, these cells have not been well studied and have been largely overlooked. To better characterize the intra-renal lymphocytes, we extensively perfused C57BL/6J mice with PBS and then isolated mononuclear cells for flow cytometry analysis. We observed T cells, B cells, and NK cells in normal mice kidneys after extensive perfusion. Approximately 50% of kidney T lymphocytes expressed intermediate levels of CD3 (CD3^int T cells). Similar to liver and lung, a high percentage of unconventional CD3 ⁺CD4^-CD8^- double-negative T cells was observed in normal mice kidneys, from which 11% expressed B220 antigen. Unlike the spleen and blood, the classic CD4⁺ and CD8⁺ T lymphocytes in the kidney had a high proportion of activated CD69⁺ and effector/memory CD44-CD62L ligand phenotypes. Also, a small percentage of CD4 ⁺CD25⁺forkhead box p3⁺ and NKT cells was observed in perfused and exanguinated kidneys. In addition, a distinct TCR repertoire was found on intra-renal conventional and unconventional T cells compared with those from the spleen. Finally, after 24 h of renal ischemia reperfusion injury (IRI), increased production of cytokines IFN-γ and TNF-α by CD4⁺ and CD8⁺ T cells, isolated from perfused kidneys, was observed. These data suggest that some of these cells harbored in the kidney could be implicated in the immune response of the IRI pathogenic process.