Functional effector memory T cells enrich the peritoneal cavity of patients treated with peritoneal dialysis.

The frequency and severity of episodes of peritonitis adversely affect the structure and function of the peritoneal membrane in patients treated with peritoneal dialysis (PD), but the underlying mechanisms are not well understood. Alterations in the phenotype and function of resident peritoneal cells may contribute. Because effector memory T cells play a pivotal role in maintaining peripheral tissue immunity, we hypothesized that these cells may initiate or perpetuate the peritoneal inflammatory response. Here, we characterized the phenotype and effector function of peritoneal memory T cells. We found that functional effector memory T cells capable of mounting long-term recall responses enrich the peritoneal cavity of PD patients. Peritoneal T cells were able to mount a Th1-polarized response to recall antigens, and these responses were greater in peritoneal T cells compared with T cells in the peripheral blood. We also observed that the peritoneal T cells had altered telomeres; some cells had ultrashort telomeres, suggesting a highly differentiated local population. In summary, we describe a resident population of memory T cells in the peritoneum of PD patients and speculate that these cells form part of the first line of defense against invading pathogens.