The relationship between CD4+CD25+CD127- regulatory T cells and inflammatory response and outcome during shock states

Abstract

Introduction: Although regulatory T lymphocytes (Tregs) have a pivotal role in preventing autoimmune diseases and limiting chronic inflammatory conditions, they may also block beneficial immune responses by preventing sterilizing immunity to certain pathogens.

Methods: To determine whether naturally occurring Treg cells have a role in inflammatory response and outcome during shock state we conducted an observational study in two adult ICUs from a university hospital. Within 12 hours of admission, peripheral whole blood was collected for the measurement of cytokines and determination of lymphocyte count. Sampling was repeated at day three, five and seven. Furthermore, an experimental septic shock was induced in adult Balb/c mice through caecal ligation and puncture.

Results: Forty-three patients suffering from shock (26 septic, 17 non septic), and 7 healthy volunteers were included. The percentage of Tregs increased as early as 3 days after the onset of shock, while their absolute number remained lower than in healthy volunteers. A similar pattern of Tregs kinetics was found in infected and non infected patients. Though there was an inverse correlation between severity scores and Tregs percentage, the time course of Tregs was similar between survivors and non survivors. No relation between Tregs and cytokine concentration was found. In septic mice, although there was a rapid increase in Treg cells subset among splenocytes, antibody-induced depletion of Tregs before the onset of sepsis did not alter survival.

Conclusions: These data argue against a determinant role of Tregs in inflammatory response and outcome during shock states.

Figure 1

Treg cells kinetics during shock. Regulatory T lymphocytes (Treg) cells are defined as CD4⁺CD25⁺CD127^- lymphocytes. Percentages of Tregs among CD4⁺ lymphocytes, as well as absolute count are determined in shock patients within 12 hours of admission, and then at days three, five and seven. Seven healthy volunteers served as controls. (a) Examples of Tregs percentage determination in a healthy volunteer (left panel) and a septic shock patient on admission (right panel). (b) Time-course of Tregs absolute count and (c) Percentage in patients with shock. * P < 0.03 patients vs. healthy volunteers.

Figure 2

Treg cells kinetics according to outcome in septic shock patients. * P = 0.02 septic survivors vs. septic non survivors. Treg, regulatory T lymphocytes.

Figure 3

Correlation between Tregs and severity on admission. Regulatory T lymphocytes (Tregs) percentages are inversely correlated to arterial lactate concentration (P = 0.01) and Sepsis-related Organ Failure Assessment (SOFA) score (P = 0.0001).

Figure 4

NK cells kinetics during shock. Time-course of natural killer (NK) cells absolute count and percentage (among total lymphocytes) in patients with shock. * P < 0.01 patients vs. healthy volunteers.

Figure 5

Sepsis increases Tregs percentage in mice. Twenty-four hours after caecal ligation and puncture (CLP), proportion of regulatory T lymphocytes (Treg) cells among splenocytes (CD4⁺CD25⁺Foxp3⁺ cells) is determined (n = 6 per group) (a). In some experiments, Tregs were depleted by using anti-CD25 antibody prior to sepsis induction. Depletion was highly effective with less than 1% of Tregs remaining 24 hours after the (b, B) last antibody injection as compared with (b, A) control animals.

Figure 6

Survival according to the regulatory T lymphocytes status in septic mice. Antibody-mediated depletion of CD25⁺ cells does not alter survival during caecal ligation and puncture (n = 20 per group, P = 0.62).

Figure 7

TNF-α plasma concentration according to the regulatory T lymphocytes status in septic mice. Antibody-mediated depletion of CD25⁺ cells does not influence TNF-α plasma concentration during caecal ligation and puncture (n = 6 per group).