MIF and rheumatoid arthritis: While MIF has protective roles to play in immunity against pathogens, including Salmonella typhimurium, Aspergillus fumigatus, Trypanosoma cruzi and Klebsiella pneumoniae (167, 171–173), it has pathological, pro-inflammatory roles in animal models of disease, including systemic lupus erythematosus (SLE), multiple sclerosis (MS) and rheumatoid arthritis (RA) (152).