Airway allergen exposure stimulates bone marrow eosinophilia partly via IL-9.
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 microg) of an anti-mouse IL-9 monoclonal antibody (clone D9302C12) or its vehicle. A third group was given 50 microg 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.
Sitkauskiene
Brigita
B
The Lung Pharmacology Group, Department of Respiratory Medicine and Allergology, Institute of Internal Medicine, Göteborg University, Guldhedsgatan 10A, 413 46 Gothenburg, Sweden. Brigita.Sitkauskiene@kmu.lt
Rådinger
Madeleine
M
Bossios
Apostolos
A
Johansson
Anna-Karin
AK
Sakalauskas
Raimundas
R
Lötvall
Jan
J
D000818:Animals; D001854:Bone Marrow Cells / Q000187:drug effects / Q000276:immunology* / Q000473:pathology*; D001855:Bone Marrow Diseases / Q000139:chemically induced / Q000276:immunology* / Q000473:pathology; D015848:Interleukin-5 / Q000276:immunology*; D016906:Interleukin-9 / Q000276:immunology*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D010047:Ovalbumin; D011657:Pulmonary Eosinophilia / Q000139:chemically induced / Q000276:immunology* / Q000473:pathology; D012130:Respiratory Hypersensitivity / Q000139:chemically induced / Q000276:immunology* / Q000473:pathology
D015848:Interleukin-5; D016906:Interleukin-9; D010047:Ovalbumin