IL5 and primary progressive multiple sclerosis: Furthermore, some studies have reported elevated cytokine levels in PPMS patients, including serum levels of IL-2, IL-4, IL-5, IL-10, IL-17, and IL-12p70, as well as pleural levels of IFN-γ, IL-6, and IL-8, suggesting that biologic therapies targeting these inflammatory cytokines might offer potential benefits.