Low Th17 cells in patients with cystic fibrosis and allergic broncho-pulmonary aspergillosis.

BACKGROUND

Allergic bronchopulmonary aspergillosis (ABPA) is a hypersensitivity response to the allergens of Aspergillus fumigatus, which is the most frequently isolated fungus from the sputum of cystic fibrosis (CF) patients. Because a low number of Th17 lymphocytes is associated with the risk of fungal infections, we investigated inflammatory markers, Th17 cells, and T-cell polarization in CF patients with ABPA.

METHODS

We analyzed the levels of inflammatory markers, blood counts, chemokines, cytokines, and T cell subsets in blood and sputum of CF subjects to elucidate the immunological factors associated with CF patients with Aspergillus fumigatus (AF) positive sputum (AFS) or with ABPA.

RESULTS

We observed that AFS+ patients have higher sputum and blood IL-6 levels than AF-negative sputum (AFS) patients. Analysis of blood memory T-helper subsets associated with Th1, Th2, and Th17 polarization among circulating CD45RA-/CD4+ memory T-cell subsets showed higher numbers of CCR4/CCR6/CXCR3 and CCR4/CCR6/CXCR3 memory CD4 cells in AFS+ compared to AFS subjects. Further analysis of Th17-related subsets and IL-17 secreting T cells in subjects with AFS+ showed that those with ABPA have statistically significantly lower levels of Th17 cells as compared to those without ABPA.

CONCLUSION

In CF, AF airway colonization is associated with increased blood counts of Th17-related subsets. However, CF patients with ABPA exhibit lower numbers of CCR4+/CCR6+/CXCR3+ memory CD4 cells and IL-17-secreting CD4 cells compared to control subjects and CF patients without AF sensitization.