Airway allergen exposure stimulates bone marrow eosinophilia partly via IL-9

Brigita Sitkauskiene¹^,2^,3 , Madeleine Rådinger¹ , Apostolos Bossios¹ , Anna-Karin Johansson¹ , Raimundas Sakalauskas² and Jan Lötvall¹

¹The Lung Pharmacology Group, Department of Respiratory Medicine and Allergology, Institute of Internal Medicine, Göteborg University, Guldhedsgatan 10A, 413 46 Gothenburg, Sweden

²Department of Pulmonology and Immunology, Kaunas University of Medicine, Eiveniu 2, 50009 Kaunas, Lithuania

³Lab of Pulmonology, Institute for Biomedical Research, Kaunas University of Medicine, Eiveniu 4, 50009 Kaunas, Lithuania

author email corresponding author email

Respiratory Research 2005, 6:33doi:10.1186/1465-9921-6-33


Published:	11 April 2005

Abstract

Background

Interleukin (IL)-9 is a Th2-derived cytokine with pleiotropic biological effects, which recently has been proposed as a candidate gene for asthma and allergy. We aimed to evaluate the therapeutic effect of a neutralizing anti-IL-9 antibody in a mouse model of airway eosinophilic inflammation and compared any such effect with anti-IL-5 treatment.

Methods

OVA-sensitized Balb/c mice were intraperitoneally pretreated with a single dose (100 μg) of an anti-mouse IL-9 monoclonal antibody (clone D9302C12) or its vehicle. A third group was given 50 μg of a monoclonal anti-mouse IL-5 antibody (TRFK-5) or its vehicle. Animals were subsequently exposed to OVA on five days via airways. Newly produced eosinophils were labelled using 5-bromo-2'-deoxyuridine (BrdU). BrdU⁺eosinophils and CD34⁺cell numbers were examined by immunocytochemistry. After culture and stimulation with OVA or PMA+IC, intracellular staining of IL-9 in bone marrow cells from OVA-exposed animals was measured by Flow Cytometry. The Mann-Whitney U-test was used to determine significant differences between groups.

Results

Anti-IL-9 significantly reduced bone marrow eosinophilia, primarily by decrease of newly produced (BrdU⁺) and mature eosinophils. Anti-IL-9 treatment also reduced blood neutrophil counts, but did not affect BAL neutrophils. Anti-IL-5 was able to reduce eosinophil numbers in all tissue compartments, as well as BrdU⁺eosinophils and CD34⁺progenitor cells, and in all instances to a greater extent than anti-IL-9. Also, FACS analysis showed that IL-9 is over-expressed in bone marrow CD4⁺cells after allergen exposure.

Conclusions

Our data shows that a single dose of a neutralizing IL-9 antibody is not sufficient to reduce allergen-induced influx of newly produced cells from bone marrow to airways. However, in response to allergen, bone marrow cells over-express IL-9. This data suggest that IL-9 may participate in the regulation of granulocytopoiesis in allergic inflammation.