Peripheral Erythrocytes Decrease upon Specific Respiratory Challenge with Grass Pollen Allergen in Sensitized Mice and in Human Subjects

<div><p>Background and Aims</p><p>Specific hyper-responsiveness towards an allergen and non-specific airway hyperreactivity both impair quality of life in patients with respiratory allergic diseases. We aimed to investigate cellular responses following specific and non-specific airway challenges locally and systemically in i) sensitized BALB/c mice challenged with grass pollen allergen Phl p 5, and in ii) grass pollen sensitized allergic rhinitis subjects undergoing specific airway challenge in the Vienna Challenge Chamber (VCC).</p><p>Methods and Results</p><p>BALB/c mice (n = 20) were intraperitoneally immunized with grass pollen allergen Phl p 5 and afterwards aerosol challenged with either the specific allergen Phl p 5 (n = 10) or the non-specific antigen ovalbumin (OVA) (n = 10). A protocol for inducing allergic asthma as well as allergic rhinitis, according to the united airway concept, was used. Both groups of exposed mice showed significantly reduced physical activity after airway challenge. Specific airway challenge further resulted in goblet cell hyperplasia, enhanced mucous secretion, intrapulmonary leukocyte infiltration and lymphoid follicle formation, associated with significant expression of IL-4, IL-5 and IL-13 in splenocytes and also partially in lung tissue. Concerning circulating blood cell dynamics, we observed a significant drop of erythrocyte counts, hemoglobin and hematocrit levels in both mouse groups, challenged with allergen or OVA. A significant decrease in circulating erythrocytes and hematocrit levels after airway challenges with grass pollen allergen was also found in grass pollen sensitized human rhinitis subjects (n = 42) at the VCC. The effects on peripheral leukocyte counts in mice and humans however were opposed, possibly due to the different primary inflammation sites.</p><p>Conclusion</p><p>Our data revealed that, besides significant leukocyte dynamics, particularly erythrocytes are involved in acute hypersensitivity reactions to respiratory allergens. A rapid recruitment of erythrocytes to the lungs to compensate for hypoxia is a possible explanation for these findings.</p></div

Physical activity after airway challenge.

<p>Rearing of Phl p 5-allergic in allergen (red squares) or nonspecific antigen (black points) challenged mice. Data are mean ± SD and n = 5 mice/group. ***, p<0.001.</p

Changes in number of peripheral blood cells before and after airway challenge with grass-pollen mix in subjects with allergic rhinitis, after 4<b> </b>h (<i>group 1</i>) or 2<b> </b>h (<i>group 2</i>) of allergen exposure; follow-up data shows the respective blood cell counts 6–21 days after airway allergen challenge.

<p>Data are median (minimum, maximum); *p<0.05, **p<0.01, ***p<0.001 compared to baseline values;</p>a<p>Significantly more intra-individual decreases than increases from baseline.</p

Demographic and clinical characteristics of study subjects.

<p>Data are mean±standard deviation, SPT = Skin-Prick-Test, RAST = Radioallergosorbent Test, FEV1 = forced expiratory volume in 1 second.</p

Specific and nonspecific airway provocation of allergic mice: impact on blood cells.

<p>(<b>A</b>) RBC, (<b>B</b>) HGB and (<b>C</b>) HCT levels of naïve, non-sensitized versus sensitized and Phl p 5 nebulized (red squares) and OVA challenged mice (black points) after airway challenge. Data are mean ± SD and n = 5 mice/group. *, p<0.05, **, p<0.01 and n.s. means not significant. (<b>D</b>) White blood cell counts (WBC) from naïve versus sensitized and Phl p 5 challenged (red squares) or OVA aerosolized mice (black points).</p

Aerosol allergen challenge specifically attracts leukocytes to lungs.

<p>(<b>A</b>) Volume of lymphoid follicles V/S (fol, epi) per total surface area of airway epithelial basal membrane [µm] (<b>B</b>) and percentage of airway walls containing eosinophils in fields of view (FOVs). Lung histology representatives with respect to lymphoid follicles from Phl p 5 sensitized and (<b>C</b>) OVA challenged or (<b>D</b>) Phl p 5 challenged and (<b>E</b>) naïve mice. Data are presented by boxplots (median, quartiles, minimum and maximum) and n = 5 mice/group. *, p<0.05, **, p<0.01 and n.s. means not significant.</p

Goblet cell metaplasia, mucus production, lymphoid follicles and infiltration of airways with eosinophils after aerosol challenge.

<p>(<b>A</b>) Volume of epithelial mucus, (<b>B</b>) fraction of epithelial basal membrane covered by goblet cells. Representative lung histology from (<b>C</b>) Phl p 5 sensitized and OVA challenged (<b>D</b>), Phl p 5 sensitized and Phl p 5 challenged (<b>E</b>) naïve mice. Data are presented by boxplots (median, quartiles, minimum and maximum) and n = 5 mice/group. *, p<0.05.</p