Cockroach allergen-induced eosinophilic airway inflammation in HLA-DQ/human CD4(+) transgenic mice.

Airway eosinophilic inflammation is a characteristic feature of allergic asthma. Exposure to allergens produced by the German cockroach (Blattella germanica) is a risk factor for allergic disease in genetically predisposed individuals, and has been linked to an increase in asthma morbidity among cockroach-sensitive inner city children. To determine the role and contribution of specific HLA class II in the pathogenesis of allergic airway inflammation in cockroach-induced asthma, we generated double-transgenic, double-knockout mice expressing human HLA-DQ8, HLA-DQ6, and CD4 molecules in the absence of mouse class II and mouse CD4. Mice were actively immunized and later challenged intranasally with cockroach allergen extract. These mice developed bronchoalveolar lavage fluid (BALF) eosinophilia and pulmonary eosinophilia. This was accompanied by an increase in total protein levels, IL-5, and IL-13 in BALF. There were also elevated levels of cockroach-specific serum IgG1 and total serum IgE. Histological analysis revealed peribronchial and perivascular eosinophilic inflammation in cockroach-treated mice. Other pathologic changes in the airways were epithelial cell hypertrophy and mucus production. Treatment with anti-DQ mAb significantly reduced pulmonary and BALF eosinophilia in cockroach allergen-sensitized mice. Abeta(0) mice and transgenic mice expressing human CD4 molecule alone (without class II) or human HLA-DQ8 molecule (without CD4) treated in the same fashion showed no eosinophilia in bronchoalveolar fluid and no pulmonary parenchymal inflammation. Our results provide direct evidence that HLA-DQ molecules and CD4 T cells mediate cockroach-induced eosinophilic inflammation in the airways.

HLA-DQ/human CD4-restricted immune response to cockroach allergens in transgenic mice.

We investigated the immune response to the German cockroach (Blattella germanica), and one of its major antigens, Blattella germanica group 5 (Bla g 5), in a double-transgenic, double-knockout mouse expressing human HLA-DQ8, HLA-DQ6 and CD4 molecules in the absence of mouse class II and mouse CD4. Transgenic mice were primed and challenged with CR extract or individual synthetic peptides representing Bla g 5. Strong T-cell responses to CR extract were detected in both HLA-DQ/hCD4+ transgenic mice. The responses were two times lower in mice expressing HLA-DQ molecule in the context of mouse CD4. Under similar treatment, no responses were found in the double-knockout Abetadegrees/mCD4degrees mice and in mice expressing human CD4 molecule alone. HLA-DQ/hCD4+ mice produced primarily interleukin (IL)-5, IL-10, and IL-13. Minimal amounts of IL-4 were detected only in HLA-DQ6/ hCD4+ mice. Interferon (IFN)-gamma production was low in both transgenic mouse, suggesting a predominantly T-helper 2 (Th2)-type response. Cockroach allergen extract immunized HLA-DQ8/hCD4+ mice recognized only one of the 20 peptides of Bla g 5 while HLA-DQ6/hCD4+ mice responded primarily to three peptides. Primed with individual peptides, both HLA-DQ/hCD4+ mice responded maximally to peptides 10 (residues 91-110) and 17 (residues 161-180). In addition, HLA-DQ6/hCD4+ mice responded to peptide 16 (residues 151-170). Thus, peptides 10 and 17 contained the major HLA-DQ-restricted hCD4+ T-cell epitopes and could be recognized by both HLA-DQ8 and HLA-DQ6 transgenic mice. Transgenic mice represent a new tool for investigating the immune responses to cockroach allergen. Our results suggest that therapeutic strategies aimed at developing antagonist peptides might be a useful treatment (immunotherapy) for allergic asthma.

Sympathetic withdrawal and forearm vasodilation during vasovagal syncope in humans.

Our aim was to determine whether sympathetic withdrawal alone can account for the profound forearm vasodilation that occurs during syncope in humans. We also determined whether either vasodilating beta 2-adrenergic receptor or nitric oxide (NO) contributes to this dilation. Forearm blood flow was measured bilaterally in healthy volunteers (n = 10) by using plethysmography during two bouts of graded lower body negative pressure (LBNP) to syncope. In one forearm, drugs were infused via a brachial artery catheter while the other forearm served as a control. In the control arm, forearm vascular resistance (FVR) increased from 77 +/- 7 units at baseline to 191 +/- 36 units with -40 mmHg of LBNP (P < 0.05). Mean arterial pressure fell from 94 +/- 2 to 47 +/- 4 mmHg just before syncope, and all subjects demonstrated sudden bradycardia at the time of syncope. At the onset of syncope, there was sudden vasodilation and FVR fell to 26 +/- 6 units (P < 0.05 vs. baseline). When the experimental forearm was treated with bretylium, phentolamine, and propranolol, baseline FVR fell to 26 +/- 2 units, the vasoconstriction during LBNP was absent, and FVR fell further to 16 +/- 1 units at syncope (P < 0.05 vs. baseline). During the second trial of LBNP, mean arterial pressure again fell to 47 +/- 4 mmHg and bradycardia was again observed. Treatment of the experimental forearm with the NO synthase inhibitor NG-monomethyl-L-arginine in addition to bretylium, phentolamine, and propranolol significantly increased baseline FVR to 65 +/- 5 units but did not prevent the marked forearm vasodilation during syncope (FVR = 24 +/- 4 vs. 29 +/- 8 units in the control forearm). These data suggest that the profound vasodilation observed in the human forearm during syncope is not mediated solely by sympathetic withdrawal and also suggest that neither beta 2-adrenergic-receptor-mediated vasodilation nor NO is essential to observe this response.