CD4 T CELLS: LESSONS LEARNED FROM ASTHMA

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Cystic Fibrosis (CF) is a common, lethal genetic disease that arises from defects in CF transmembrane conductance regulator (CFTR). The majority of patients with CF die of progressive respiratory failure and despite over a half a century of research on CF lung disease, our knowledge of its pathogenesis remains incomplete. Numerous studies have focused on the airway epithelium and the neutrophil, yet on the tissue level CF is a lymphocytic disease. Both asthma and allergic bronchopulmonary aspergillosis (ABPA) are commonly found in patients with CF and represent an exuberant CD4 Th2 cell inflammatory response, suggesting that CD4 Th2 cells may be important in CF airway disease as well. Although a number of studies have examined the role of CFTR in airway epithelium, little is known about CFTR function in bone marrow derived cells. Since T lymphocytes express CFTR, they may well be affected by CFTR defects. We have studied the inflammatory response to Aspergillus fumigatus hyphal antigens in the CF airway using two different murine models of CF (delta F508 and CFTR knock out). In both animals we have found that compared to wild type, CF mice (delta F508 and CFTR knock out) generate excessive airway inflammation in response to A. fumigatus exposure. This inflammatory response is characterized by airway eosinophilia and epithelial mucus hypersecretion. In addition, CD4 T cells from A. fumigatus exposed CF mice (delta F508 and CFTR knock out) produce more interleukin-4 (IL-4) than controls, while CD4 T cells from non-exposed delta F508 and CFTR knock out mice have a spontaneous CD4 Th2 bias following in vitro activation. Together, our studies clearly demonstrate that the absence of functional CFTR results in exaggerated airway inflammation in response to A. fumigatus exposure and this appears to be associated with a Th2 bias. Moreover, they show that CD4 T cells from two different CF murine strains have an inherent CD4 Th2 bias even in the absence of A. fumigatus exposure. Our future focus will be to determine if the Th2 bias arises from a deficit of CFTR on CD4 T cells or if it results from a CFTR deficit in another constituent of the immune system or the from the lung airway environment. We will also investigate if correction of CFTR expression by CD4 T cells resolves excessive airway inflammation in response to A. fumigatus exposure and inherent Th2 bias. In addition we will begin studies to understand the mechanism of how a deficit in CFTR on the CD4 T cell results in increased IL-4 production. Our log term goal is to define how inflammatory cell defects contribute to airway destruction in CF.