Eosinophilopoiesis in a murine model of allergic airway eosinophilia: involvement of bone marrow IL-5 and IL-5 receptor alpha

• The airway inflammation in asthma is dominated by eosinophils. The aim of this study was to elucidate the contribution of newly produced eosinophils in airway allergic inflammation and to determine mechanisms of any enhanced eosinophilopoiesis. OVA-sensitized BALB/c mice were repeatedly exposed to allergen via airway route. Newly produced cells were identified using a thymidine analog, 5-bromo-2'-deoxyuridine, which is incorporated into DNA during mitosis. Identification of IL-5-producing cells in the bone marrow was performed using FACS. Bone marrow CD3+ cells were enriched to evaluate IL-5-protein release in vitro. Anti-IL-5-treatment (TRFK-5) was given either systemically or directly to the airways. IL-5R-bearing cells were localized by immunocytochemistry. Repeated airway allergen exposure caused prominent airway eosinophilia after three to five exposures, and increased the number of immature eosinophils in the bone marrow. Up to 78% of bronchoalveolar lavage (BAL) granulocytes were 5-bromo-2'-deoxyuridine positive. After three allergen exposures, both CD3+ and non-CD3 cells acquired from the bone marrow expressed and released IL-5-protein. Anti-IL-5 given i.p. inhibited both bone marrow and airway eosinophilia. Intranasal administration of anti-IL-5 also reduced BAL eosinophilia, partly via local effects in the airways. Bone marrow cells, but not BAL eosinophils, displayed stainable amounts of the IL-5R alpha-chain. We conclude that the bone marrow is activated by airway allergen exposure, and that newly produced eosinophils contribute to a substantial degree to the airway eosinophilia induced by allergen. Airway allergen exposure increases the number of cells expressing IL-5-protein in the bone marrow. The bone marrow, as well as the lung, are possible targets for anti-IL-5-treatment.

Subject headings

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Lungmedicin och allergi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Respiratory Medicine and Allergy (hsv//eng)

Keyword

Administration

Intranasal

Allergens/administration & dosage/immunology

Animals

Antibodies

Monoclonal/administration & dosage

Bone Marrow Cells/chemistry/*immunology/pathology

Bromodeoxyuridine/administration & dosage/analysis

Bronchoalveolar Lavage Fluid/chemistry/immunology

Cell Movement/immunology

Coloring Agents/administration & dosage/analysis

Disease Models

Animal

Eosinophils/chemistry/*immunology/pathology

Granulocytes/chemistry/immunology/pathology

Hematopoiesis/*immunology

Hematopoietic Stem Cells/chemistry/immunology/pathology

Inflammation/immunology/pathology

Injections

Intraperitoneal

Interleukin-5/immunology/*physiology

Leukocyte Count

Male

Mice

Mice

Inbred BALB C

Ovalbumin/administration & dosage/immunology

Pulmonary Eosinophilia/*immunology/metabolism/pathology

Receptors

Interleukin/analysis/*physiology

Receptors

Interleukin-5

Time Factors

Publication and Content Type

ref (subject category)

art (subject category)