Interleukin-33 (IL-33) is a member of the IL-1 family and an important cytokine in the immune system, involved in various allergic diseases and inflammatory reactions. As an alarmin, IL-33 is mainly expressed by epithelial cells in the intestines, skin, and lungs when damaged or dissolved. Due to its specific expression in barrier sites, IL-33 serves as a "detector" for viral and parasitic infections, harmful substances (tobacco, pollutants, etc.), or allergens invading the body.
The complete IL-33 molecule consists of three parts: the chromatin-binding domain (CBD), protease-sensitive domain (PSD), and receptor-binding domain (RBD). Due to the strong binding capacity of CBD to nuclear chromatin, IL-33 is not easily released from dying cells, thereby prolonging its half-life.
