New insight into systemic mastocytosis mediated by cytokines IL-1β and IL-33: Potential inhibitory effect of IL-37.

Systemic mastocytosis in various forms is characterized by mast cell (MC) infiltration of the bone marrow and other internal organs. The most common form is the indolent one with life expectancy similar to the normal population, while the systemic aggressive myeloproliferative type presents serious damage to various organs and is associated with mature and immature atypical mast cells. In systemic mastocytosis patients, MCs could be activated with consequent severe anaphylactic reactions, along with other symptoms. MCs, which are reactive to a variety of external factors such as allergens or other inflammatory or physical stimuli, derive from pluripotent cellular progenitor CD34 which leaves the bone marrow as CD34/CD17 for implantation in the tissues where they reach maturation. MCs participate in the innate and adaptive immune system where they play a role in host defense. Activation of MCs occurs through the binding of IgE to FcεRI receptor, and initiates the phosphorylation and activation of the p38 tyrosine MAP kinase. After various reactions there is a subsequent translation and generation of pro-inflammatory cytokines which are strongly linked to allergic inflammation and mastocytosis. Human cytokine interleukin-37 (IL-37), a unique IL-1β family member, has strong protective and anti-inflammatory properties, influencing cellular metabolism. We investigated the effect of IL-37 on inflammation in mastocytosis and report that the hematopoietic expression of IL-37 can reduce the inflammatory state in this disease. IL-37 limits excessive inflammation, which suggests that IL-37 may be beneficial to the metabolic and inflammatory process and is a candidate as a potential new therapeutic agent.