Cytotoxic T cells expressing the co-stimulatory receptor NKG2 D are increased in cigarette smoking and COPD

<p>Abstract</p> <p>Background</p> <p>A suggested role for T cells in COPD pathogenesis is based on associations between increased lung cytotoxic T lymphocyte (CD8⁺) numbers and airflow limitation. CD69 is an early T cell activation marker. Natural Killer cell group 2 D (NKG2D) receptors are co-stimulatory molecules induced on CD8⁺T cells upon activation. The activating function of NKG2 D is triggered by binding to MHC class 1 chain-related (MIC) molecules A and B, expressed on surface of stressed epithelial cells. The aim of this study was to evaluate the expression of MIC A and B in the bronchial epithelium and NKG2 D and CD69 on BAL lymphocytes in subjects with COPD, compared to smokers with normal lung function and healthy never-smokers.</p> <p>Methods</p> <p>Bronchoscopy with airway lavages and endobronchial mucosal biopsy sampling was performed in 35 patients with COPD, 21 healthy never-smokers and 16 smokers with normal lung function. Biopsies were immunohistochemically stained and BAL lymphocyte subsets were determined using flow cytometry.</p> <p>Results</p> <p>Epithelial CD3⁺lymphocytes in bronchial biopsies were increased in both smokers with normal lung function and in COPD patients, compared to never-smokers. Epithelial CD8⁺lymphocyte numbers were higher in the COPD group compared to never-smoking controls. Among gated CD3⁺cells in BAL, the percentage of CD8⁺NKG2D⁺cells was enhanced in patients with COPD and smokers with normal lung function, compared to never-smokers. The percentage of CD8⁺CD69⁺cells and cell surface expression of CD69 were enhanced in patients with COPD and smokers with normal lung function, compared to never-smokers. No changes in the expression of MIC A or MIC B in the airway epithelium could be detected between the groups, whereas significantly decreased soluble MICB was detected in bronchial wash from smokers with normal lung function, compared to never-smokers.</p> <p>Conclusions</p> <p>In COPD, we found increased numbers of cytotoxic T cells in both bronchial epithelium and airway lumen. Further, the proportions of CD69- and NKG2D-expressing cytotoxic T cells in BAL fluid were enhanced in both subjects with COPD and smokers with normal lung function and increased expression of CD69 was found on CD8⁺cells, indicating the cigarette smoke exposure-induced expansion of activated cytotoxic T cells, which potentially can respond to stressed epithelial cells.</p

NKG2D-dependent effector function of bronchial epithelium activated alloreactive T cells.

Allogeneic hematopoietic stem cell transplantation (SCT) has emerged as a curative therapeutic option. However, The role of graft-versus-host disease in lung injury after SCT has still to be determined.In the present study primary bronchial epithelial cells and the bronchial epithelial cell line BEAS-2B were used to investigate immune responses of allogeneic CD8(+) T- cells directed against respiratory epithelial cells.Following stimulation with irradiated bronchial epithelial cells, CD8(+) T-cells produced significant amounts of IFN-gamma, upregulated alloantigen activation markers and proliferated highly compared to T-cells stimulated with IL-2 alone. Furthermore, cytotoxicity assays demonstrated that bronchial epithelial cell specific and Granzyme B-mediated cytolytic activity was induced in CD8(+) T cells. Generation of NK-, NK-like T cells (NKT cells), cytokine-induced killer (CIK) or lymphokine activated killer (LAK) cells could be excluded by phenotyping, culture conditions and neglectable lytic activity following stimulation with IL-2 alone. Inhibition experiments showed that lysis of bronchial epithelial cells was not MHC I restricted but depended on natural killer group 2, member D (NKG2D) signaling, a stimulatory receptor initially shown to be expressed on NK cells.Our data imply that respiratory epithelium has antigen presenting function and directly alloactivates cytotoxic CD8(+) T cells which show nonclassical effector function