• David Grimaldi, Lionel Le Bourhis, Bertrand Sauneuf, Agnès Dechartres, Christophe Rousseau, Fatah Ouaaz, Maud Milder, Delphine Louis, Jean-Daniel Chiche, Jean-Paul Mira, Olivier Lantz, and Frédéric Pène.
• Réanimation médicale, Hôpital Cochin AP-HP, 27 rue du Faubourg Saint Jacques, 75014, Paris, France. dgrimaldi@ch-versailles.fr.
• Intensive Care Med. 2014 Feb 1; 40 (2): 192-201.

PurposeIn between innate and adaptive immunity, the recently identified innate-like mucosal-associated invariant T (MAIT) lymphocytes display specific reactivity to non-streptococcal bacteria. Whether they are involved in bacterial sepsis has not been investigated. We aimed to assess the number and the time course of circulating innate-like T lymphocytes (MAIT, NKT and γδ T cells) in critically ill septic and non-septic patients and to establish correlations with the further development of intensive care unit (ICU)-acquired infections.MethodsWe prospectively enrolled consecutive patients with severe sepsis and septic shock. Controls were critically ill patients with non-septic shock and age-matched healthy subjects. Circulating innate-like lymphocytes were enumerated using a flow cytometry assay at day 1, 4 and 7.ResultsOne hundred and fifty six patients (113 severe bacterial infections, 36 non-infected patients and 7 patients with severe viral infections) and 26 healthy subjects were enrolled into the study. Patients with severe bacterial infections displayed an early decrease in MAIT cell count [median 1.3/mm(3); interquartile range (0.4-3.2)] as compared to control healthy subjects [31.1/mm(3) (12.1-45.2)], but also to non-infected critically ill patients [4.3/mm(3) (1.4-13.2)] (P < 0.0001 for all comparisons). In contrast NKT and γδ T cell counts did not differ between patients groups. The multivariate analysis identified non-streptococcal bacterial infection as an independent determinant of decrease in MAIT cell count. Furthermore, the incidence of ICU-acquired infections was higher in patients with persistent MAIT cell depletion.ConclusionsThis large human study provides valuable information about MAIT cells in severe bacterial infections. The persistent depletion of MAIT cells is associated with the further development of ICU-acquired infections.

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