Alteration of Balance between Myeloid Dendritic Cells and Plasmacytoid Dendritic Cells in Peripheral Blood of Patients with Asthma

156

145

It was previously shown that administration of recombinant human Fms-like tyrosine kinase receptor-3 ligand (Flt3L) before allergen challenge of sensitized mice suppresses the cardinal features of asthma through unclear mechanisms. Here, we show that Flt3L dramatically alters the balance of conventional to plasmacytoid dendritic cells (pDCs) in the lung favoring the accumulation of pDCs. Selective removal of pDCs abolished the antiinflammatory effect of Flt3L, suggesting a regulatory role for these cells in ongoing asthmatic inflammation. In support, we found that immature pDCs are recruited to the lungs of allergen-challenged mice irrespective of Flt3L treatment. Selective removal of pDCs during allergen challenge enhanced airway inflammation, whereas adoptive transfer of cultured pDCs before allergen challenge suppressed inflammation. Experiments in which TLR9 agonist CpG motifs were administered in vitro or in vivo demonstrated that pDCs were antiinflammatory irrespective of their maturation state. These effects were mediated through programmed death-1/programmed death ligand 1 interactions, but not through ICOS ligand, IDO, or IFN-α. These findings suggest a specialized immunoregulatory role for pDCs in airway inflammation. Enhancing the antiinflammatory properties of pDCs could be employed as a novel strategy in asthma treatment.

Section: Discussionmentioning

confidence: 81%

An Anti-Inflammatory Role for Plasmacytoid Dendritic Cells in Allergic Airway Inflammation

Kool

Nimwegen

Willart

et al. 2009

156

145

“…Indeed, pDCs have been shown capable of mediating both Th1 and Th2 polarization (15,34). Furthermore, studies in humans show that both mDCs as well as pDCs are present in the allergic immune response to allergen (35,36) and, in patients with allergic asthma, allergen challenge increased both mDC and pDC numbers with an overall greater percent increase in pDCs (37). Clearly, the precise role of different dendritic cells subsets in allergic diseases is far from resolved.…”

Section: Discussionmentioning

confidence: 99%

Acute, but Not Resolved, Influenza A Infection Enhances Susceptibility to House Dust Mite-Induced Allergic Disease

Al-Garawi

Fattouh

Walker

et al. 2009

The impact of respiratory viral infections on the emergence of the asthmatic phenotype is a subject of intense investigation. Most experimental studies addressing this issue have used the inert Ag OVA with controversial results. We examined the consequences of exposure to a low dose of the common aeroallergen house dust mite (HDM) during the course of an influenza A infection. First, we delineated the kinetics of the immune-inflammatory response in the lung of mice following intranasal infection with influenza A/PR8/34. Our data demonstrate a peak response during the first 10 days, with considerable albeit not complete resolution at day 39 postinfection (p.i.). At day 7 p.i., mice were exposed, intranasally, to HDM for 10 consecutive days. We observed significantly enhanced eosinophilic inflammation, an expansion in Th2 cells, enhanced HDM-specific IgE and IgG1 responses and increased mucous production. Furthermore, lung mononuclear cells produced enhanced IFN-␥ and IL-5, unchanged IL-13, and reduced IL-4. These immunologic and structural changes lead to marked lung dysfunction. This allergic phenotype occurs at a time when there is a preferential increase in plasmacytoid dendritic cells over myeloid dendritic cells, activated CD8؉ T cells, and increased IFN-␥ production, all of which have been proposed to inhibit allergic responses. In contrast, the inflammatory response elicited by HDM was reduced when exposure occurred during the resolution phase (day 40 p.i.). Interestingly, this was not associated with a reduction in sensitization. Thus, the proinflammatory environment established during an acute influenza A infection enhances Th2-polarized immunity to a low dose of HDM and precipitates marked lung dysfunction.

“…In two preliminary experiments, no increase in CD207 (the Langerhans marker) was detected on low MLR-capacity patient M , but these data are far from conclusive. A posttrauma increase in plasmacytoid or lymphoid-derived DC precursors could greatly affect overall DC APC capacity (15,16,49). The plasmacytoid DC population is suggested to preferably induce regulatory T cells (15,16).…”

Section: Discussionmentioning

confidence: 99%

Failure of Monocytes of Trauma Patients to Convert to Immature Dendritic Cells is Related to Preferential Macrophage-Colony-Stimulating Factor-Driven Macrophage Differentiation

De¹,

Laudański²,

Miller-Graziano

2003

Following trauma, increased inflammatory monokine activation and depressed APC function can occur simultaneously. These contradictory monocyte (Mφ) dysfunctions could result if postinjury Mφ differentiation preferentially favored inflammatory macrophage (Mac) differentiation over development into the most potent APC, dendritic cells (DC). In this report, Mφ of trauma patients with a depressed MLR induction capacity are, for the first time, shown to be unable to differentiate in vitro to immature CD1a+ DC under the influence of GM-CSF and IL-4. Trauma patient Mφ that retained MLR-inducing capacity had a nonsignificant reduction in DC differentiation capacity. Only patient Mφ populations with depressed differentiation to immature DC (iDC) demonstrated depressed IL-12 and IL-15 production and a continued reduced MLR induction capacity. Neither increased IL-10 production nor decreased CD11c+ DC precursor numbers correlated with depressed Mφ-to-DC differentiation. Instead, these patients’ APC-dysfunctional Mφ populations had increased expression of inflammatory Mac phenotypes (CD64+, CD86low, HLA-DRlow) and up-regulated secretion of M-CSF. M-CSF combined with IL-6 inhibits Mφ-to-iDC differentiation and promotes Mφ-to-Mac differentiation by down-regulating GM-CSFR expression and increasing DC apoptosis. Both depressed GM-CSFR expression and increased Mφ iDC apoptosis, as well as increased expression of CD126 (IL-6R) and CD115 (M-CSFR), were detected in APC-defective patient Mφ. In vitro addition of anti-M-CSF enhanced the IL-4 plus GM-CSF-induced Mφ-to-DC differentiation of these patients. This suggests that, in trauma patients, enhanced Mφ-to-Mac differentiation with concomitant inhibited iDC development is partially due to increased circulating Mφ sensitivity to and production of M-CSF and contributes to postinjury immunoaberrations.