Immunohistochemical detection of dendritic cells in human lung tissue

Autoimmunity in chronic obstructive pulmonary disease: clinical and experimental evidence

Over the past few decades, neutrophils and macrophages had co-occupied center stage as the critical innate immune cells underlying the pathobiology of cigarette smoke-induced chronic obstructive pulmonary disease and lung parenchymal destruction (i.e., emphysema). While chronic exposure to smoke facilitates the recruitment of innate immune cells into the lung, a clear role for adaptive immunity in emphysema has emerged. Evidence from human studies specifically point to a role for recruitment and activation of pathogenic lymphocytes and lung antigen-presenting cells in emphysema; similarly, animal models have confirmed a significant role for autoimumnity in progressive smoke-induced emphysema. Increased numbers of activated antigen-presenting cells, Th1 and Th17 cells, have been associated with smoke-induced lung inflammation and production of the canonical cytokines of these cells, IFN-γ and IL-17, correlates with disease severity. These exciting new breakthroughs could open new avenues for developing effective new therapies for smoke-induced emphysema.

Lung myeloid dendritic cells coordinately induce TH1 and TH17 responses in human emphysema

Exposure to tobacco smoke activates innate and adaptive immune responses that in long-term smokers have been linked to diseases of the lungs, cardiovascular system, joints, and other organs. The destruction of lung tissue that underlies smoking-induced emphysema has been associated with T helper 1 cells that recognize the matrix protein elastin. Factors that result in the development of such autoreactive T cells in smokers remain unknown but are crucial for further understanding the pathogenesis of systemic inflammatory diseases in smokers. Here, we show that lung myeloid dendritic cells were sufficient to induce T helper 1 and T helper 17 responses in CD4 T cells. T helper 1 and 17 cells are invariably present in lungs from patients with emphysema but not in lungs from normal individuals. Interleukin-17A, a canonical T helper 17 cytokine, enhanced secretion of CCL20, a chemoattractant for dendritic cells, and matrix metalloproteinase 12, a potent elastolytic proteinase, from lung macrophages. Thus, although diverse lung factors potentially contribute to T helper effector differentiation in vivo, lung myeloid dendritic cells direct the generation of pathogenic T cells and support a feedback mechanism that sustains both inflammatory cell recruitment and lung destruction. This mechanism may underlie disease in other elastin-rich organs and tissues.

Lung dendritic cell expression of maturation molecules increases with worsening chronic obstructive pulmonary disease

RATIONALE

Dendritic cells (DCs) have not been well studied in chronic obstructive pulmonary disease (COPD), yet their integral role in activating and differentiating T cells makes them potential participants in COPD pathogenesis.

OBJECTIVES

To determine the expression of maturation molecules by individual DC subsets in relationship to COPD stage and to expression of the acute activation marker CD69 by lung CD4(+) T cells.

METHODS

We nonenzymatically released lung leukocytes from human surgical specimens (n = 42) and used flow cytometry to identify three DC subsets (mDC1, mDC2, and pDC) and to measure their expression of three costimulatory molecules (CD40, CD80 and CD86) and of CD83, the definitive marker of DC maturation. Spearman nonparametric correlation analysis was used to identify significant correlations between expression of DC maturation molecules and COPD severity.

MEASUREMENTS AND MAIN RESULTS

Expression of CD40 by mDC1 and mDC2 and of CD86 by mDC2 was high regardless of GOLD stage, but CD80 and CD83 on these two DC subsets increased with disease progression. pDC also showed significant increases in expression of CD40 and CD80. Expression of all but one of the DC molecules that increased with COPD severity also correlated with CD69 expression on lung CD4(+) T cells from the same patients, with the exception of CD83 on mDC2.

CONCLUSIONS

This cross-sectional study implies that COPD progression is associated with significant increases in costimulatory molecule expression by multiple lung DC subsets. Interactions with lung DCs may contribute to the immunophenotype of CD4(+) T cells in advanced COPD. Clinical trial registered with www.clinicaltrials.gov (NCT00281229).

Expression of blood dendritic cell antigens (BDCAs) by CD1a+ human pulmonary cells

BACKGROUND

Myeloid and plasmacytoid dendritic cell (DC) subsets have been recently identified in the human lung based on their differential expression of Blood DC Antigens 1-3 (BDCAs). We investigated the expression of these antigens by isolated human pulmonary CD1a(+) DCs, namely Langerhan's cells.

METHODS

Using an in vitro cell culture system we successfully isolated a population of relatively pure (>70%) CD1a(+) cells from human lung tissue (n=5 subject samples) and stained these with antibodies against the myeloid DC markers BDCA1 (CD1c) and BDCA3 (CD303), the plasmacytoid DC marker BDCA2 (CD141), the Langerhan's cell marker Langerin and the maturation marker CD83.

RESULTS

Among different subject samples, the isolated CD1a(+) cells showed variable expression of Langerin, BDCAs and CD83. Interestingly, in two subject samples, which contained >70% CD83(+) mature CD1a(+) cells, >50% of the cells were positive for all of the BDCAs.

CONCLUSIONS

We conclude that isolated pulmonary CD1a(+) DCs in vitro have the capacity to express both myeloid and plasmacytoid BDCA markers and that rather than subset restriction in pulmonary DCs, a significant degree of flexibility/plasticity can be induced, albeit experimentally.