Regulatory T cells in cystic fibrosis lung disease. More answers, more questions

Regulatory T cells in lung disease and transplantation

Pulmonary disease can refer to the disease of the lung itself or the pulmonary manifestations of systemic diseases, which are often connected to the malfunction of the immune system. Regulatory T (Treg) cells have been shown to be important in maintaining immune homeostasis and preventing inflammatory damage, including lung diseases. Given the increasing amount of evidence linking Treg cells to various pulmonary conditions, Treg cells might serve as a therapeutic strategy for the treatment of lung diseases and potentially promote lung transplant tolerance. The most potent and well-defined Treg cells are Foxp3-expressing CD4+ Treg cells, which contribute to the prevention of autoimmune lung diseases and the promotion of lung transplant rejection. The protective mechanisms of Treg cells in lung disease and transplantation involve multiple immune suppression mechanisms. This review summarizes the development, phenotype and function of CD4+Foxp3+ Treg cells. Then, we focus on the therapeutic potential of Treg cells in preventing lung disease and limiting lung transplant rejection. Furthermore, we discussed the possibility of Treg cell utilization in clinical applications. This will provide an overview of current research advances in Treg cells and their relevant application in clinics.

Update on Innate and Adaptive Immunity in Cystic Fibrosis

Cystic fibrosis (CF) pathophysiology is hallmarked by excessive inflammation and the inability to resolve lung infections, contributing to morbidity and eventually mortality. Paradoxically, despite a robust inflammatory response, CF lungs fail to clear bacteria and are susceptible to chronic infections. Impaired mucociliary transport plays a critical role in chronic infection but the immune mechanisms contributing to the adaptation of bacteria to the lung microenvironment is not clear. CFTR modulator therapy has advanced CF life expectancy opening up the need to understand changes in immunity as CF patients age. Here, we have summarized the current understanding of immune dysregulation in CF.

Mucosal Immunity in Cystic Fibrosis

The highly complex and variable genotype-phenotype relationships observed in cystic fibrosis (CF) have been an area of growing interest since the discovery of the CF transmembrane conductance regulator (CFTR) gene >30 y ago. The consistently observed excessive, yet ineffective, activation of both the innate and adaptive host immune systems and the establishment of chronic infections within the lung, leading to destruction and functional decline, remain the primary causes of morbidity and mortality in CF. The fact that both inflammation and pathogenic bacteria persist despite the introduction of modulator therapies targeting the defective protein, CFTR, highlights that we still have much to discover regarding mucosal immunity determinants in CF. Gene modifier studies have overwhelmingly implicated immune genes in the pulmonary phenotype of the disease. In this context, we aim to review recent advances in our understanding of the innate and adaptive immune systems in CF lung disease.

The impact of lung microbiota dysbiosis on inflammation

Host-microbiota interaction plays fundamental roles in the homeostasis of mucosal immunity. Dysbiosis of intestinal microbiota has been demonstrated to participate in various immune responses and many multifactorial diseases. Study of intestinal microbiota has moved beyond the consequences of dysbiosis to the causal microbiota associated with diseases. However, studies of pulmonary microbiota and its dysbiosis are still in their infancy. Improvement of culture-dependent and -independent techniques has facilitated our understanding of lung microbiota that not only exists in healthy lung tissue but also exerts great impact on immune responses under both physiological and pathological conditions. In this review, we summarize recent progresses of lung microbiota dysbiosis and its impact on the local immune system that determines the balance of tolerance and inflammation. We discuss the causal roles of pulmonary dysbiosis under disease settings, and propose that the interaction between lung microbiota and host is critical for establishing the immune homeostasis in lung.

Mucosal-associated invariant T cells: new players in CF lung disease?

The past decade has witnessed a surge in research centered around exploring the role of the enigmatic innate immune-like lymphocyte MAIT cell in human disease. Recent evidence has led to the elucidation of its role as a potent defender at mucosal surfaces including lungs due to its capacity to mount a formidable immediate response to bacterial pathogens. MAIT cells have a unique attribute of recognizing microbial ligands in conjunction with non-classical MHC-related protein MR1. Recent studies have demonstrated their contribution in the pathogenesis of chronic pulmonary disorders including asthma and chronic obstructive pulmonary disease. Several cellular players including innate immune cells are active contributors in the immune imbalance present in cystic fibrosis(CF) lung. This immune dysregulation serves as a central pivot in disease pathogenesis, responsible for causing immense structural damage in the CF lung. The present review focuses on understanding the role of MAIT cells in CF lung disease. Future studies directed at understanding the possible relationship between MAIT cells and regulatory T cells (Tregs) in CF lung disease could unravel a holistic picture where a combination of antimicrobial effects of MAIT cells and anti-inflammatory effects of Tregs could be exploited in synergy to alleviate the rapid deterioration of lung function in CF lung disease due to the underlying complex interplay between persistent infection and inflammation.

Inhibition of histone-deacetylase activity rescues inflammatory cystic fibrosis lung disease by modulating innate and adaptive immune responses

Background

Chronic lung disease resulting from dysfunctional cystic fibrosis transmembrane conductance regulator (CFTR) and NFκB-mediated neutrophilic-inflammation forms the basis of CF-related mortality. Here we aimed to evaluate if HDAC inhibition controls Pseudomonas-aeruginosa-lipopolysaccharide (Pa-LPS) induced airway inflammation and CF-lung disease.

Methods

For in vitro experiments, HEK293-cells were transfected with IL-8 or NFκB-firefly luciferase, and SV40-renilla- luciferase reporter constructs or ΔF508-CFTR-pCEP, followed by treatment with suberoylanilide hydroxamic acid (SAHA), Trichostatin-A (TSA) and/or TNFα. For murine studies, Cftr^+/+ or Cftr^−/− mice (n = 3) were injected/instilled with Pa-LPS and/or treated with SAHA or vehicle control. The progression of lung disease was monitored by quantifying changes in inflammatory markers (NFκB), cytokines (IL-6/IL-10), neutrophil activity (MPO, myeloperoxidase and/or NIMP-R14) and T-reg numbers.

Results

SAHA treatment significantly (p < 0.05) suppresses TNFα-induced NFκB and IL-8 reporter activities in HEK293-cells. Moreover, SAHA, Tubacin (selective HDAC6-inhibitor) or HDAC6-shRNAs controls CSE-induced ER-stress activities (p < 0.05). In addition, SAHA restores trafficking of misfolded-ΔF508-CFTR, by inducing protein levels of both B and C forms of CFTR. Murine studies using Cftr^+/+ or Cftr^−/− mice verified that SAHA controls Pa-LPS induced IL-6 levels, and neutrophil (MPO levels and/or NIMP-R14), NFκB-(inflammation) and Nrf2 (oxidative-stress marker) activities, while promoting FoxP3⁺ T-reg activity.

Conclusion

In summary, SAHA-mediated HDAC inhibition modulates innate and adaptive immune responses involved in pathogenesis and progression of inflammatory CF-lung disease.

Electronic supplementary material

The online version of this article (10.1186/s12931-017-0705-8) contains supplementary material, which is available to authorized users.

Biofilms and host response - helpful or harmful

Biofilm infections are one of the modern medical world's greatest challenges. Probably, all non-obligate intracellular bacteria and fungi can establish biofilms. In addition, there are numerous biofilm-related infections, both foreign body-related and non-foreign body-related. Although biofilm infections can present in numerous ways, one common feature is involvement of the host response with significant impact on the course. A special characteristic is the synergy of the innate and the acquired immune responses for the induced pathology. Here, we review the impact of the host response for the course of biofilm infections, with special focus on cystic fibrosis, chronic wounds and infective endocarditis.

Innate and Adaptive Immunity in Cystic Fibrosis

Cystic fibrosis (CF) lung disease is characterized by persistent and unresolved inflammation, with elevated proinflammatory and decreased anti-inflammatory cytokines, and greater numbers of immune cells. Hyperinflammation is recognized as a leading cause of lung tissue destruction in CF. Hyper-inflammation is not solely observed in the lungs of CF patients, since it may contribute to destruction of exocrine pancreas and, likely, to defects in gastrointestinal tract tissue integrity. Paradoxically, despite the robust inflammatory response, and elevated number of immune cells (such as neutrophils and macrophages), CF lungs fail to clear bacteria and are more susceptible to infections. Here, we have summarized the current understanding of immune dysregulation in CF, which may drive hyperinflammation and impaired host defense.