Changes in Gene Transcription and Immunophenotypes Following Mepolizumab Treatment for Asthma

Inclusion Criteria: * Age ≥ 18 years old. * Diagnosis of SEA by a health care provider * History of an absolute eosinophil count ≥ 300/mm\^3 * Prescription for mepolizumab provided during course of routine clinical care but mepolizumab not yet started Exclusion Criteria: * Age \< 18 years old. * Pregnancy. * Currently using or have used within 3 months of the initial baseline visit any biologic or immunomodulatory therapy with the exception of #3. * Currently using or any prior use of rituximab. * History of upper/lower respiratory tract infection or asthma exacerbation within the previous four weeks of the first baseline visit. * Any prior history of malignancy, autoimmune disease, or immune deficiency. * Any other significant medical issue as determined by the principal investigator.