Abstract
Background:
Asthma is a predominantly TH2 cell-dominated inflammatory disease characterized by airway inflammation and a major public health concern affecting millions of persons. The Tec family tyrosine kinase IL-2-inducible T-cell kinase (Itk) is primarily expressed in T cells and critical for the function and differentiation of TH cells. Itk(-/-) mice have a defective TH2 response and are not susceptible to allergic asthma.
Objective:
We sought to better understand the role of Itk signaling in TH differentiation programs and in the development and molecular pathology of allergic asthma.
Methods:
Using a murine model of allergic airway inflammation, we dissected the role of Itk in regulating TH cell differentiation through genetic ablation of critical genes, chromatin immunoprecipitation assays, and house dust mite-driven allergic airway inflammation.
Results:
Peripheral naive Itk(-/-) CD4(+) T cells have substantially increased transcripts and expression of the prototypic TH1 genes Eomesodermin, IFN-γ, T-box transcription factor (T-bet), and IL-12Rβ1. Removal of IFN-γ on the Itk(-/-) background rescues expression of TH2-related genes in TH cells and allergic airway inflammation in Itk(-/-) mice. Furthermore, small hairpin RNA-mediated knockdown of Itk in human peripheral blood T cells results in increased expression of mRNA for IFN-γ and T-bet and reduction in expression of IL-4.
Conclusion:
Our results indicate that Itk signals suppress the expression of IFN-γ in naive CD4(+) T cells, which in a positive feed-forward loop regulates the expression of TH1 factors, such as T-bet and Eomesodermin, and suppress development of TH2 cells and allergic airway inflammation.
Keywords:
AHR; APC; Airways hyperresponsiveness; Antigen-presenting cell; BALF; Bronchoalveolar lavage fluid; CNS; ChIP; Chromatin immunoprecipitation; Conserved noncoding sequence; DKO; Double knockout; Eomes; Eomesodermin; HDM; House dust mite; IFN-γ; IL-2–inducible T-cell kinase; Itk; P/I; Phorbol 12-myristate 13-acetate/ionomycin; Quantitative PCR; Small hairpin RNA; T(H)2; T-bet; T-box transcription factor; T-cell receptor; TCR; Tec kinase; WT; Wild type; allergic asthma; qPCR; shRNA.