The kinetics of T regulatory cells in shock: beyond sepsis

Pathways mediating resolution of inflammation: when enough is too much

Patients with critical illness, and in particular sepsis, are now recognized to undergo unifying, pathogenic disturbances of immune function. Whilst scientific and therapeutic focus has traditionally been on understanding and modulating the initial pro-inflammatory limb, recent years have witnessed a refocusing on the development and importance of immunosuppressive 'anti-inflammatory' pathways. Several mechanisms are known to drive this phenomenon; however, no overriding conceptual framework justifies them. In this article we review the contribution of pro-resolution pathways to this phenotype, describing the observed immune alterations in terms of either a failure of resolution of inflammation or the persistence of pro-resolution processes causing inappropriate 'injurious resolution'-a novel hypothesis. The dysregulation of key processes in critical illness, including apoptosis of infiltrating neutrophils and their efferocytosis by macrophages, are discussed, along with the emerging role of specialized cell subtypes Gr1(+) CD11b(+) myeloid-derived suppressor cells and CD4(+) CD25(+) FoxP3(+) T-regulatory cells.

An increased alveolar CD4 + CD25 + Foxp3 + T-regulatory cell ratio in acute respiratory distress syndrome is associated with increased 30-day mortality

Purpose

Cell therapy may become an option for lung injury treatment. However, no data are available on the alveolar presence and time course of CD4+ CD25 + Foxp3 + T-regulatory lymphocyte cells (Tregs) in acute respiratory distress syndrome (ARDS). Accordingly, we (1) measured the ratio of CD4 + CD25 + Foxp3 + Tregs to all (CD4+) lymphocytes in the bronchoalveolar lavage (BAL) of ARDS patients and of control subjects without lung disease and (2) assessed their impact on 30-day mortality.

Methods

In a prospective study, the ratios of CD4 + CD25 + Foxp3 + T-regulatory cells to all CD4+ cells were measured (FACS) within 24 h of the patients’ ICU referral in the BAL and in the blood of 47 patients with ARDS (32 males, 15 females; mean age 44 years ±13) as well as in 8 controls undergoing elective abdominal surgery (5 men, 3 women; mean age 49 years ±4). BAL concentrations of several cytokines were also measured in ARDS patients.

Results

Tregs were detected in the BAL of control subjects and ARDS patients. However, the mean ratio of Tregs to all CD4+ lymphocytes was threefold greater in ARDS non-survivors (16.5 %; p = 0.025) and almost twofold greater in ARDS survivors (9.0 %; p = 0.015) compared to controls (5.9 %). Multivariate Cox regression analysis revealed the ratio of CD4 + CD25 + Foxp3 + T-regulatory lymphocytes to all CD4+ lymphocytes in the BAL to be an important and independent prognostic factor for 30-day survival (HR 6.5; 95 % CI, 1.7–25; p = 0.006).

Conclusion

An increased T-regulatory cell ratio in the admission BAL of patients with ARDS is an important and independent risk factor for 30-day mortality.