The conflicting and largely inconsequential effects of systemic administration of IL-10 in systemic- and organ-specific autoimmune diseases (i.e., systemic lupus erythematosus, psoriasis, type 1 diabetes, Crohn’s disease, rheumatoid arthritis, and multiple sclerosis) in preclinical and clinical studies [34,35,36] suggest possible compartmentalization of the action of IL-10. This evidence concerns the gene IL10 and multiple sclerosis.