Both percentage of γδ T lymphocytes and CD3 expression are reduced during septic shock

Objective: The mechanisms involved during sepsis-induced immunosuppression are far from being extensively established. The objective of the present study was to investigate whether two characteristics of T cells were altered in this situation: the percentage of circulating gamma delta T lymphocytes and the level of CD3 expression on T lymphocytes. Design: Observational study. Setting: Adult intensive care units in a university hospital. Patients: Patients with septic shock (n = 21) and healthy individuals (n = 21). Interventions: None. Measurements and Main Results: In patients, we first observed the decreased percentage of yB T lymphocytes in peripheral blood (1% [0.7-3.1], median [interquartile range]) in comparison with healthy individuals (3.5% [2.1-4.8]). Regarding CD3, we measured a highly significant decrease of its expression on both alpha beta and gamma delta T lymphocytes from patients (p < .005), whereas the CD3 mean fluorescence intensities ratio (gamma delta/alpha beta) was not affected: 2.2 [2.1-2.4] and 2.1 [1.9-2.3] in healthy individuals and septic patients, respectively. The magnitude in the decrease of CD3 expression was thus similar in alpha beta and gamma delta cells, suggesting a common down-regulation mechanism for both T-cell lineages. Conclusions: Combined with a reduced percentage of monocytes expressing human leukocyte antigen-DR, a reduced CD3 expression may be involved in the failure of antigen presentation depicted after septic shock, whereas the diminished percentage of circulating 78 T cells could be partly responsible for the elevated incidence of secondary infections. These two observations constitute additional pieces of the complex puzzle of sepsisinduced immunosuppression.