The current paradigm surrounding allergen-mediated T helper type 2 (Th2) immune responses in the lung suggests an almost hegemonic role for T cells. Our studies propose an alternative hypothesis implicating eosinophils in the regulation of pulmonary T cell responses. In particular, ovalbumin (OVA)-sensitized/challenged mice devoid of eosinophils (the transgenic line PHIL) have reduced airway levels of Th2 cytokines relative to the OVA-treated wild type that correlated with a reduced ability to recruit effector T cells to the lung. Adoptive transfer of Th2-polarized OVA-specific transgenic T cells (OT-II) alone into OVA-challenged PHIL recipient mice failed to restore Th2 cytokines, airway histopathologies, and, most importantly, the recruitment of pulmonary effector T cells. In contrast, the combined transfer of OT-II cells and eosinophils into PHIL mice resulted in the accumulation of effector T cells and a concomitant increase in both airway Th2 immune responses and histopathologies. Moreover, we show that eosinophils elicit the expression of the Th2 chemokines thymus- and activation-regulated chemokine/CCL17 and macrophage-derived chemokine/CCL22 in the lung after allergen challenge, and blockade of these chemokines inhibited the recruitment of effector T cells. In summary, the data suggest that pulmonary eosinophils are required for the localized recruitment of effector T cells.

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Tumor-associated eosinophilia has been observed in numerous human cancers and several tumor models in animals, however, the details surrounding this eosinophilia remain largely undefined and anecdotal. We used a B16-F10 melanoma cell injection model to demonstrate that eosinophil infiltration of tumors occurred from the earliest palpable stages with significant accumulations only in the necrotic and capsule regions. Furthermore, the presence of diffuse extracellular matrix staining for eosinophil major basic protein was restricted to the necrotic areas of tumors indicating that eosinophil degranulation was limited to this region. Antibody-mediated depletion of CD4 + T cells and adoptive transfer of eosinophils suggested, respectively, that the accumulation of eosinophils is not associated with Th2-dependent immune responses and that recruitment is a dynamic ongoing process, occurring throughout tumor growth. Ex vivo migration studies have identified what appears to be a novel chemotactic factor(s) released by stressed/dying melanoma cells, suggesting that the accumulation of eosinophils in tumors occurs, in part, through a unique mechanism dependent on a signal(s) released from areas of necrosis. Collectively, these studies demonstrate that the infiltration of tumors by eosinophils is an early and persistent response that is spatial restricted. More importantly, these data also show that the mechanism(s) that elicits this host response occurs independent of immune surveillance, suggesting that eosinophils are part of an early inflammatory reaction at the site of tumorigenesis.

Insulin resistance and dysregulation of free fatty acid (FFA) metabolism are core defects in type 2 diabetic (T2DM) and obese normal glucose tolerant (NGT) individuals. Impaired muscle mitochondrial function (reduced ATP synthesis) also has been described in insulin-resistant T2DM and obese subjects. We examined whether reduction in plasma FFA concentration with acipimox improved ATP synthesis rate and altered reactive oxygen species (ROS) production. Eleven NGT obese and 11 T2DM subjects received 1) OGTT, 2) euglycemic insulin clamp with muscle biopsy, and 3) 1H-magnetic resonance spectroscopy of tibialis anterior muscle before and after acipimox (250 mg every 6 h for 12 days). ATP synthesis rate and ROS generation were measured in mitochondria isolated from muscle tissue ex vivo with chemoluminescence and fluorescence techniques, respectively. Acipimox 1) markedly reduced the fasting plasma FFA concentration and enhanced suppression of plasma FFA during oral glucose tolerance tests and insulin clamp in obese NGT and T2DM subjects and 2) enhanced insulin-mediated muscle glucose disposal and suppression of hepatic glucose production. The improvement in insulin sensitivity was closely correlated with the decrease in plasma FFA in obese NGT (r = 0.81) and T2DM (r = 0.76) subjects (both P < 0.001). Mitochondrial ATP synthesis rate increased by >50% in both obese NGT and T2DM subjects and was strongly correlated with the decrease in plasma FFA and increase in insulin-mediated glucose disposal (both r > 0.70, P < 0.001). Production of ROS did not change after acipimox. Reduction in plasma FFA in obese NGT and T2DM individuals improves mitochondrial ATP synthesis rate, indicating that the mitochondrial defect in insulin-resistant individuals is, at least in part, reversible.

Allergen-induced respiratory inflammation facilitates and/or elicits the extravasation of proinflammatory leukocytes by well-understood mechanisms that mediate the movement of multiple cell types. The nonspecific character of these pathways led us to hypothesize that circulating cancer cells use similar mechanisms, promoting secondary tumor formation at distal sites. To test this hypothesis, the frequency of metastasis to the lung as a function of allergic pulmonary inflammation was assessed following the i.v. injection of B16-F10 melanoma cells in mice. These studies showed that allergen-induced pulmonary inflammation resulted in a >3-fold increase in lung metastases. This increase was dependent on CD4 + T-cell activities; however, it occurred independent of the induced eosinophilia associated with allergen provocation. Interventional strategies showed that existing therapeutic modalities for asthma, such as inhaled corticosteroids, were sufficient to block the enhanced pulmonary recruitment of cancer cells from circulation. Additional mechanistic studies further suggested that the ability of circulating cancer cells to extravasate to surrounding lung tissues was linked to the activation of the vascular endothelium via one or more GA icoupled receptors. Interestingly, a survey of a clinical breast cancer surgical database showed that the incidence of asthma was higher among patients with lung metastases. Thus, our data show that allergic respiratory inflammation may represent a risk factor for the development of lung metastases and suggest that amelioration of the pulmonary inflammation associated with asthma will have a direct and immediate benefit to the 7% to 8% of breast cancer patients with this lung disease. [Cancer Res 2008;68(20):8582-9]