LAUSR

Objective The role of Th1 and Th17 lymphocyte responses in human infection and sepsis of elderly patients has yet to be clarified. Design A prospective observational study of patients with sepsis, infection only and healthy controls. Setting The acute medical wards and intensive care units in a 1000 bed university hospital. Patients 32 patients with sepsis, 20 patients with infection, and 20 healthy controls. Patients and controls were older than 65 years of age. Patients with recognised underlying immune compromise were excluded. Methods Phenotype, differentiation status and cytokine production by T lymphocytes were determined by flow cytometry. Measurements The differentiation states of circulating CD3+, CD4+, and CD8+ T cells were characterised as naive (CD45RA+, CD197+), central memory (CD45RA-, CD197+), effector memory (CD45RA-, CD197-), or terminally differentated (CD45RA+, CD197-). Expression of IL-12 and IL-23 receptors, and the transcription factors T-bet and RORγt, was analysed in circulating T lymphocytes. Expression of interferon- γ and IL-17A were analysed following stimulation in vitro. Results CD4+ T cells from patients with infection predominantly expressed effector-memory or terminally differentiated phenotypes but CD4+ T cells from patients with severe sepsis predominantly expressed naive phenotypes (p<0.0001). CD4+ T cells expressing IL-23 receptor were lower in patients with sepsis compared to patients with infection alone (p = 0.007). RORγt expression by CD4+ T cells was less frequent in patients with sepsis (p<0.001), whereas T-bet expressing CD8+ T cells that do not express RORγt was lower in the sepsis patients. HLA-DR expression by monocytes was lower in patients with sepsis. In septic patients fewer monocytes expressed IL-23. Conclusion Persistent failure of T cell activation was observed in patients with sepsis. Sepsis was associated with attenuated CD8+Th1 and CD4+Th17 based lymphocyte response.