Yi L, et al. - Researchers probed the expression and clinical correlations of costimulatory molecules on peripheral T-cell subsets of severe sepsis (SS) patients. They evaluated the blood samples of patients with community-acquired pneumonia-associated SS and healthy controls (HCs). An activated T-cell phenotype was exhibited by early-stage SS patients. Authors noted a presentation of imbalanced OX40 and 4-1BB expression on regulatory T cells (Tregs) and conventional T cells (Tconvs) could contribute to a functional imbalance of Tregs/Tconvs. The 28-day mortality of SS was predicted by the frequency of CD4+CD27+ T cells and OX40+ on CD4+CD27-CD28- T cells.