The present application discloses a novel fusion peptide of IL-2 and IL-33 and its use. It comprises a biologically active domain of Interleukin-2 (IL-2) or a biologically active fragment or homolog thereof, and a biologically active domain of Interleukin-33 (IL-33) or a biologically active fragment or homolog thereof. The two portions can be linked by a linker sequence. The application discloses that combination therapies using IL-2 and IL-33 or a therapy using the IL233 fusion protein are effective in preventing or treating diseases and disorders such as autoimmune diseases and disorders, inflammation, etc. Depending on the subject's disease or disorder, the compositions of the invention are useful for preventing certain symptoms, treating the disease, and alleviating at least some of the symptoms.