Both percentage of gammadelta 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 gammadelta 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 gammadelta 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 alphabeta and gammadelta T lymphocytes from patients (p < .005), whereas the CD3 mean fluorescence intensities ratio (gammadelta/alphabeta) 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 alphabeta and gammadelta 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 gammadelta T cells could be partly responsible for the elevated incidence of secondary infections. These two observations constitute additional pieces of the complex puzzle of sepsis-induced immunosuppression.