No abstract

Eosinophil differentiation is thought to occur by the action of interleukin (IL)-5 on CD34(+) progenitor cells. The allergen-induced increase in eosinophil numbers in isolated airway preparations in vitro, and detection of increased numbers of circulating CD34(+) cells in atopic subjects, led us to the hypothesis that the eosinophil infiltration of the airway in asthma may result from local mucosal differentiation, in addition to recruitment from the bone marrow. We examined CD34(+) cell numbers by immunohistochemistry and IL-5 receptor alpha (IL-5Ralpha) messenger RNA (mRNA) expression by in situ hybridization in bronchial biopsies from atopic asthmatic patients, and from atopic and nonatopic control subjects. CD34(+) cell numbers were increased in the airway in atopic asthmatic and atopic nonasthmatic subjects. In contrast, CD34(+)/ IL-5Ralpha mRNA+ cells were increased in asthmatic subjects when compared with both atopic and nonatopic control subjects. Airway numbers of CD34(+)/IL-5Ralpha mRNA+ cells were correlated to airway caliber in asthmatic subjects and to eosinophil numbers. These findings support the concept that eosinophils may differentiate locally in the airway in asthma.

No abstract

CCR8 was initially described as a Th2 cell-restricted receptor, but this has not been fully tested in vivo. The present study used ex vivo and in vivo approaches to examine the distribution and functional significance of CCR8 among CD4+ T cells. Populations of cytokine-secreting CD4+ T cells were generated in primed mice with Th1 or Th2 cell-mediated pulmonary granulomas, respectively elicited by i.v. challenge with either Mycobacteria bovis purified protein derivative- or Schistosoma mansoni egg Ag (SEA)-coated beads. Cytokine-producing CD4+ T cells were isolated from Ag-stimulated draining lymph node cultures by positive selection. Quantitative analysis of cytokine mRNA indicated enriched populations of IFN-γ-, IL-4-, and IL-10-producing cells. Analysis of chemokine receptor mRNA indicated that IL-10+ cells selectively expressed CCR8 in the SEA bead-elicited type 2 response. The IL-10+CCR8+ populations were CD25+ and CD44+ but lacked enhanced Foxp3 expression. Adoptive transfer to naive recipients indicated that IL-10+ T cells alone could not transfer type 2 inflammation. Analysis of SEA bead-challenged CCR8−/− mice indicated significantly impaired IL-10 production as well as reductions in granuloma eosinophils. Adoptive transfer of CD4+CCR8+/+ T cells corrected cytokine and inflammation defects, but the granuloma eosinophil recruitment defect persisted when donor cells were depleted of IL-10+ cells. Accordingly, local IL-10 production correlated with CCR8 ligand (CCL1) expression and the appearance of CCR8+ cells in granulomatous lungs. Thus, IL-10-producing, CCR8+CD4+CD25+CD44+ T cells are generated during SEA challenge, which augment the Th2-mediated eosinophil-rich response to the parasite Ags.

Dendritic cell (DC) recruitment is a hallmark event in antigen (Ag)-challenged lungs. We previously reported models for analyzing DC migration and activation in the lung after Th1-or Th2-eliciting pathogen Ag-bead challenge. To determine the role of chemokines in DC mobilization, we applied this analysis to CCR1, CCR2, CCR5, and CCR6 chemokine receptor knockout mice. Both Mycobacteria bovis protein Ags and helminthic, Schistosoma mansoni egg Ags elicited multiple chemokines, including CCR1, CCR2, CCR5, and to a lesser extent CCR6 ligands. DCs from wild-type lungs expressed transcripts for chemokine receptors, CCR1, CCR2, CCR5, and CXCR4. In all knockout strains, CD11c؉ cells were recruited to Agbeads likely because of receptor redundancy. However, DCs in CCR2؊/؊ mice had significantly decreased MHCII and CD40 expression. This was associated with abrogated cytokine production in draining lymph node cultures. Analysis of local innate inflammation revealed a 50% reduction in macrophage recruitment in CCR2؊/؊ mice. Bone marrow chimeras of mixed CCR2؉/؉ green fluorescent protein transgenic and CCR2؊/؊ green fluorescent protein-negative cells confirmed the DC maturation defect was only among the latter population. In conclusion, CCR2 knockout confers an intrinsic DC activation defect and CCR2 ligands likely promote the local activation/maturation of inflammatory DCs.