Date

4-24-2012

UMMS Affiliation

Graduate School of Biomedical Sciences, Master of Science in Clinical Investigation (MSCI) program

Document Type

Thesis, Master's

Subjects

Theses, UMMS; Cystic Fibrosis Transmembrane Conductance Regulator; Cytokines; Lymphocytes; Mutation; Antigens, CD3

Disciplines

Biochemistry, Biophysics, and Structural Biology | Congenital, Hereditary, and Neonatal Diseases and Abnormalities | Immunology and Infectious Disease | Life Sciences | Medicine and Health Sciences | Respiratory Tract Diseases

Abstract

Background: Cystic fibrosis (CF) remains the most common fatal monogenic disease in the US, affecting 1 in 3,300 live births. CF is the result of mutations in CFTR, a chloride channel and regulator of other ion channels. The mechanisms by which CFTR mutations cause chronic lung disease in CF are not fully defined, but may include the combined effects of altered ion and water transport across the airway epithelium and aberrant inflammatory and immune responses to pathogens within the airways. We have shown that Cftr-/- mice mount an exaggerated IgE response towards Aspergillus fumigatus (Af) when compared to Cftr+/+ mice. Along with the increased IgE levels, the Cftr-/- mice had higher levels of IL-13 and IL-4, mimicking both the Th-2 biased immune responses and predilection to mounting Af-specifc IgE seen in CF patients. Herein we hypothesize that these immune aberrations are primarily due to the lack of Cftr expression in lymphocytes rather than with Cftr deficiency in the epithelium.

Results: Our results indicate that adoptive transfer experiments with Cf splenocytes confer higher IgE response to Af in host mice as compared to hosts receiving wild-type splenocytes. The predilection of Cftr-deficient lymphocytes to mount Th2 responses was confirmed by in vitro antigen recall experiments, where higher levels of IL-13 and IL-4 where seen only in the presence of Cftr-deficient lymphocytes. Conclusive data on this phenomenon were obtained with conditional Cftr knockout mice, where mice lacking Cftr in T-cell lineages developed the higher IgE titers as compared to their wild-type littermate controls. Further analysis of Cftr-deficient lymphocytes revealed an enhanced intracellular Ca 2+ flux in response to T cell receptor activation as compared to normal lymphocytes. This was accompanied by a significant increase in nuclear localization of the calcium-sensitive transcription factor NFAT, which could contribute to the enhanced secretion of IL-13 and other cytokines.

Conclusions: In summary, our data identified that CFTR dysfunction in T cells can lead directly to aberrant immune responses. This is the first instance that a CF related phenotype has been entirely modeled in vivo by selectively knocking out CFTR in the immune system. Specifically, Cftr deficient lymphocytes directed skewed responses to Aspergillus fumigatus , leading to a higher than normal IgE response. These findings implicate the lymphocyte population as a potentially important target for therapeutics directed to the treatment of CF lung disease.