Peripheral killer cells do not differentiate between asthma patients with or without fixed airway obstruction

Functionality of natural killer cells in obese asthma phenotypes

BACKGROUND

Obesity-associated asthma (OA) is a difficult to treat asthma phenotype due to its severity and poor response to inhaled steroids. Early-onset allergic (EoOA) and late-onset non-allergic (LoOA) OA are suggested subtypes of this phenotype. Natural Killer (NK) cells are key elements of innate immunity involved in cytotoxicity and immune regulation, with uncertain role in OA pathogenesis.

METHODS

Early-onset allergic and LoOA patients together with obese non-asthmatic (ONA) controls have been enrolled in the study. Peripheral blood samples have been collected for analysis. Percentages of total NK cells, CD3^- CD56^dim and CD3^- CD56^bright NK cell subsets, cytotoxic activity, intracellular interferon-γ, interleukin (IL)-10, IL-13, IL-17 secretion and activatory receptors (NKG2D, NKp46i and NKp44) have been investigated by flow cytometry. The effect of IL-12 and IL-23 stimulation on NK cells and intracellular cytokines in different groups have also been analysed and compared with unstimulated conditions.

RESULTS

Results of ONA (n = 5, age 42 ± 8), EoOA (n = 5, age 42 ± 10) and LoOA (n = 8, age 46 ± 8) patients have analysed. Body Mass Index has been found to be negatively correlated with CD69 (p = .022, r = -0.534). NKG2D receptor has been significantly low in CD56^dim cells of asthma population (p = .046). NKp44 receptor expression has increased after IL-12 stimulation in EoOA and control group (p = .02). Intracellular IL-10 content has increased in LoOA and control subjects (p = .018, p = .03) but not in the EoOA group. Intracellular IL-17 level has found be higher in allergic OA group. LoOA patients showed a decreased NK cytotoxicity compared with the early-onset asthma group (p = .05).

CONCLUSION

Our study suggests an impaired NK receptor expression, activation and reduced cytotoxicity in OA patients together with variances between different subtypes of this phenotype. This data would be beneficial for tailoring a more personalized treatment strategy combatting steroid resistance and frequent exacerbations in this group of patients.

Role of Natural Killer Cells in Airway Inflammation

Natural killer (NK) cells have an immune regulatory function as well as cytotoxicity against tumor or infected cells. In the airway, although NK cells constitute a small proportion of the resident lymphocytes, they play an important role in the pathogenesis of chronic inflammatory airway diseases by modulating immune responses. NK cells can promote allergic airway inflammation by increasing the production of type 2 cytokines and inducing eosinophil migration. The increased activity of NK cells can develop or aggravate the destruction of lung parenchymal cells. On the other hand, decreased apoptotic activity of NK cells in eosinophils can serve as an aggravating factor for allergic airway inflammation. The increase in interferon-γ-producing NK cells and the inhibition of type 2 immune response by NK cells can alleviate allergic airway inflammation. This review aims to define the roles of NK cells in chronic inflammatory diseases of lower and upper airways.

Innate and Adaptive Immune Defects in Chronic Pulmonary Aspergillosis

We evaluated the expression of biomarkers of innate and adaptive immune response in correlation with underlying conditions in 144 patients with chronic pulmonary aspergillosis (CPA). Patients with complete medical and radiological records, white cell counts, and a complete panel of CD3, CD4, CD8, CD19, and CD56 lymphocyte subsets were included. Eighty-four (58%) patients had lymphopenia. Six (4%) patients had lymphopenia in all five CD variables. There were 62 (43%) patients with low CD56 and 62 (43%) patients with low CD19. Ten (7%) patients had isolated CD19 lymphopenia, 18 (13%) had isolated CD56 lymphopenia, and 15 (10%) had combined CD19 and CD56 lymphopenia only. Forty-eight (33%) patients had low CD3 and 46 (32%) had low CD8 counts. Twenty-five (17%) patients had low CD4, 15 (10%) of whom had absolute CD4 counts <200/μL. Multivariable logistic regression showed associations between: low CD19 and pulmonary sarcoidosis (Odds Ratio (OR), 5.53; 95% Confidence Interval (CI), 1.43–21.33; p = 0.013), and emphysema (OR, 4.58; 95% CI; 1.36–15.38; p = 0.014), low CD56 and no bronchiectasis (OR, 0.27; 95% CI, 0.10–0.77; p = 0.014), low CD3 and both multicavitary CPA disease (OR, 2.95; 95% CI, 1.30–6.72; p = 0.010) and pulmonary sarcoidosis (OR, 4.94; 95% CI, 1.39–17.57; p = 0.014). Several subtle immune defects are found in CPA.