As previously discussed, congenic strains have been used to show that the Ncf1 and APLEC polymorphisms contribute to not only arthritis but also EAE (Flytzani et al., 2013; Hultqvist et al., 2004), and that Igl contributes to ovalbumin-induced airway inflammation (Rintisch et al., 2008). Here, NCF1 is linked to arthritic joint disease.