Omalizumab is used in treatment of:
Severe persistent allergic asthma pathophysiology centers on Th2 polarization with interleukin-4 and interleukin-13 driving class switch recombination from IgM to IgE mediated by AID and germline ε transcription in B cells within bronchial associated lymphoid tissue. Secreted IgE circulates at low concentration 150 ng per ml but binds extremely high affinity FcεRI alpha chain Kd 10^-10 M on mast cells and basophils through Cε3 domain interaction, sensitizing them for months despite short serum half-life two days. Upon re-exposure to perennial aeroallergen such as Dermatophagoides pteronyssinus
Ref: GINA 2023 severe asthma Omalizumab IgE; Holgate Nat Rev Immunol anti-IgE Cε3 blocks FcεRI downregulation.