T helper 17 (Th17) and regulatory T (T_reg) lymphocytes might play important roles in patients with severe sepsis. The association of Th17 or T_reg lymphocytes with survival is also unclear.

Eighty-seven patients with severe sepsis were enrolled from our intensive care units between August 2008 and July 2010. Leukocyte antigens and clinical data were determined on day 1 in all patients and on day 7 in first-year patients.

The percentages in peripheral blood mononuclear cells (PBMCs) and circulatory counts of CD4⁺ and CD8⁺ lymphocytes in survivors were higher than those in non-survivors. Th1/CD4⁺ ratios and circulatory Th1 lymphocyte counts in survivors were higher than in non-survivors. Absolute counts of Th17 and T_reg lymphocytes in survivors were higher than in non-survivors. The percentages of CD4⁺ and CD8⁺ in survivors’ PBMCs were increased after 6 days. Th17/CD4⁺ ratios and circulatory Th17 lymphocyte counts in survivors were increased after 6 days.

Higher Th1 differentiation and total CD4⁺ T lymphocyte counts were associated with higher survival. The association of circulatory Th17 and T_reg lymphocytes with mortality in severe sepsis may be due to the change in total CD4⁺ T lymphocytes. In survivors, Th17 differentiation and counts were restored.