A drug (mepolizumab) that reduces allergic inflammation will affect the function of allergy cells called eosinophils which are produced by the body in response to allergen exposure.

Inclusion Criteria:

• Males or females age 18 to 50 yrs,
• History of asthma based upon presence of asthma symptoms such as cough, shortness of breath, wheeze or chest tightness,
• positive skin-prick test to a House Dust Mite extract,
• Forced expiratory volume at one second >70% predicted pre-albuterol, > 80% predicted post albuterol
• >12% increase in Forced expiratory volume at one second following inhaled albuterol (180 µg) and/or
• airway responsiveness to methacholine (PC20 <8mg/ml).
• > 20% immediate drop in FEV1 following inhaled antigen challenge.
• Safety laboratory assessments within normal ranges (labs to include complete blood count with differential, blood urea nitrogen, creatinine, aspartate aminotransferase, alanine aminotransferase, Prothrombin time, Partial Thromboplastin Time, and platelet count)
• Female subjects of child-bearing potential must have a negative urine pregnancy test (urine HCG) within 48 hours of the methacholine challenge at Visit 2 and agree to use a reliable method of birth control for the duration of the study (reliable methods of birth control can include abstinence, barrier methods, oral contraceptives, injection contraceptives or skin absorption contraceptives).
• In the opinion of the investigator, capable and willing to grant written informed consent and cooperate with study procedures and requirements.

Exclusion Criteria:

• Use of inhaled or systemic corticosteroids or leukotriene inhibitors within 1 month of screening.
• Treatment with Omalizumab (anti-IgE) within 9 months of screening visit
• Concomitant use of any other monoclonal antibody
• Respiratory infection within 4 weeks of study
• Unstable asthma as indicated by self-report of increased symptoms or increased beta-agonist use over the previous 2 weeks.
• Female subjects who are pregnant, nursing or have a pregnancy planned during the course of study
• Current smokers (defined as smoked within the last year) or a former smoker with a history of >5 pack years.
• Major health problems such as heart disease, type I and II diabetes or lung diseases other than asthma. Decisions regarding this criteria will be based upon the judgment of the investigator.
• Previous malignancy.
• Medication other than for asthma, allergies or contraception and that the investigator feels may interfere with the conduct of study (e.g. monoamine oxidase inhibitors and B-adrenergic antagonists in any form)
• Known history of allergic reaction to previous antibody administration.
• Prior treatment with an anti-interleukin-5 monoclonal antibody,
• Use of an investigational drug within 30 days of entering the study,
• History of noncompliance with medical regimens or subjects who are considered unreliable.

Each participant was followed anywhere between 36 weeks to 45 weeks depending on treatment path.

Our small sample size limits any meaningful consideration about the mechanisms of mepolizumab's clinical action. The prolonged time commitment and inclusion of four bronchoscopies affected subject retention and limited the sample size.