Reduction of immunocompetent T cells followed by prolonged lymphopenia in severe sepsis in the elderly.

Objective: To investigate the immunological changes caused by severe sepsis in elderly patients.

Design: One-year, prospective observational study.

Setting: Emergency department and intensive care unit of a single university hospital.

Patients: Seventy-three patients with severe sepsis and 72 healthy donors.

Measurements And Main Results: In elderly septic patients (aged 65 yr and over), 3-month survival was significantly reduced compared with that for adult patients (18-64 yr) (60% vs. 89%, p < 0.01). We found that lymphopenia was prolonged for at least 21 days in elderly nonsurvivors of sepsis, while the number of lymphocytes recovered in both adult and elderly survivors of sepsis. In order to examine the immunological status of septic patients, blood samples were collected within 48 hrs of diagnosis of severe sepsis, and peripheral blood mononuclear cells were purified for flow cytometric analysis. T cell levels were significantly reduced in both adult and elderly septic patients, compared with those in healthy donors (56% and 57% reduction, respectively). Interestingly, the immunocompetent CD28+ subset of CD4+ T cells decreased, whereas the immunosuppressive PD-1+ T cells and the percentage of regulatory T cells (CD4+ T cells that are both Foxp3+ and CD25+) increased in elderly patients, especially nonsurvivors, presumably reflecting the initial signs of immunosuppression.

Conclusion: Reduction of immunocompetent T cells followed by prolonged lymphopenia may be associated with poor prognosis in elderly septic patients.