We previously confirmed that the maintenance of Treg cell numbers in asthma patients with chronic eosinophilic pneumonia may inhibit EGPA development via the action of cytokines, such as IL-10 and TGF-β, which are produced by CD4+CD25+ cells, and IL-2, which is produced by CD4+CD25− T cells [9]. Here, CD4 is linked to asthma.