Background: Dendritic cells control pulmonary immune reactions. Characteristics of dendritic cells in human bronchoalveolar lavage fluid (BALF) after allergen challenge are unknown. Methods: 7 patients with allergic asthma (median 23 years, range 19-25 years) underwent segmental challenge and were lavaged 10 min and 24 h after challenge. Dendritic cell subsets and surface markers in BALF and in peripheral blood were analysed using four-colour flow cytometry. Results: Plasmacytoid dendritic cells (pDCs, median 0.06%, range 0.01-0.08%) and myeloid dendritic cells (mDCs, median 0.47%, range 0.27-0.87%) were detectable in BALF from control segments. CD1a-positive dendritic cells in BALF were identified as a subpopulation of mDCs. Both pDCs (median 0.56%, range 0.09-1.83%) and mDCs (median 1.82%, range 0.95-2.29%) increased significantly in BALF 24 h (p = 0.018 compared with the control segments for pDCs and mDCs), but not 10 min, after allergen challenge. The percentage increase in pDCs was higher than that of mDCs after allergen challenge, as reflected by an enhanced pDC:mDC ratio after allergen challenge. In peripheral blood, there was a significant decrease in mDCs (p = 0.038) and a trend to a decrease in pDCs (p = 0.068) 24 h after allergen challenge. Analysis of dendritic cell surface molecules showed that after allergen challenge, BALF dendritic cells have a less mature phenotype compared with BALF dendritic cells from control segments. Conclusion: Using a comprehensive strategy to analyse dendritic cell subsets in human BALF, we have shown for the first time that both myeloid and plasmacytoid dendritic cells accumulate in the airway lumen after allergen challenge in patients with asthma.

NK cells and cytotoxic T lymphocytes can induce apoptosis in virus‐infected and transformed target cells via the granule exocytosis pathway. The key components of the cytolytic granules are perforin and several serine esterases, termed granzymes. While the cellular distribution of human granzymes A (GrA) and B (GrB) has been well characterized much less is known about the expression pattern of human granzyme K (GrK). In this study GrA, GrB, and GrK expression was analyzed in human peripheral blood lymphocytes using flow cytometry. There was a distinct population of GrK expressing CD8+ T cells with a CD27+/CD28+/CCR5high/CCR7–/perforin–/low/IFN‐γ+ memory‐like phenotype, while all CD56bright NK cells were also positive for GrK. In addition, GrK was also expressed in subpopulations of CD56+ T cells, CD4+ T cells, and TCRγδ+ T cells. In contrast, GrB was primarily expressed in CD56dim NK cells and differentiated memory CD8+ T cells with the CD27–/low/CD28–/low/CCR5–/low/CCR7–/CD11b+/perforinhigh phenotype. Only few CD8+ T cells expressed both GrB and GrK. GrA was found to be co‐expressed in all GrB‐ and GrK‐expressing T cells. Our findings suggest that granzyme expression during the differentiation process of memory CD8+ T cells might be as follows: GrA+/GrB–/GrK+ → GrA+/GrB+/GrK+ → GrA+/GrB+/GrK–.

Airway dendritic cells (DCs) are key regulators of pulmonary immune responses. However, information is limited regarding the characteristics of airway DCs in human lung diseases.Plasmacytoid DCs (pDCs) and myeloid DCs (mDCs) were analysed using four-colour flow cytometry in bronchoalveolar lavage fluid (BALF) from nonsmoking controls and patients with sarcoidosis, idiopathic pulmonary fibrosis (IPF) and pneumonia (in the presence or absence of immunosuppression).Compared with controls, immunocompetent patients with pneumonia displayed strongly enhanced pDC counts in BALF. In contrast, pDC counts in BALF from immunocompromised patients with pneumonia were even lower than in controls. This discrepancy was not explained by a different chemotactic milieu in the airways; all patients with pneumonia were characterised by strongly increased concentrations of the pDC-attracting chemokine, CXC chemokine ligand 10, in BALF. Patients with IPF were characterised by normal percentages of DC subtypes. However, the mDCs of patients with IPF were not as mature (CD83-positive) as those of controls. Patients with sarcoidosis displayed a unique increase in CD1a-negative mDCs in the airways. In addition, there was altered expression of costimulatory molecules (increased CD80 and decreased CD86 expression) on mDCs in patients with sarcoidosis.These data suggest that inflammatory diseases of the human lung are associated with a differential phenotype and recruitment of airway dendritic cells.

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Airway dendritic cells (DCs) control pulmonary immune responses to inhaled particles. However, the profile of function-associated surface molecules on airway DCs in smokers is unknown. In this study, function-associated surface molecules were analyzed using four-color flow cytometry on myeloid DCs (mDCs) in bronchoalveolar lavage fluid (BALF) of cigarette smokers and never-smokers. Furthermore, the lung function was assessed directly before bronchoscopy in all participants. There was a 7-fold increase in total cell numbers in BALF of smokers, as compared with never-smokers. The percentage of mDCs among BALF cells and the expression of the maturation marker CD83 on mDCs did not differ between smokers and never-smokers. However, there was a strong increase in the expression of Langerin and CD1a (markers of Langerhans cells) on mDCs of smokers. Furthermore, mDCs of smokers were characterized by an increased expression of antigen presentation markers such as CD80 and CD86. By contrast, mDCs of smokers displayed a decreased expression of the lymph node homing receptor CCR7, as compared with mDCs of never-smokers. Decreased expression of CCR7 on mDCs, but not any of the other surface molecules studied, was specifically associated with airway obstruction and pulmonary hyperinflation in smokers. In conclusion, our data suggest that smoking affects the expression profile of function-associated surface molecules on airway mDCs. We provide the first evidence that a reduced CCR7 expression on airway mDCs is associated with airflow limitation in smokers.