IL12A and Arthritis: IL-12α (p35) is a subunit of a pleiotropic cytokine IL-12 (see above) and at the same time a subunit of IL-35 (together with IL-27β), an immune-suppressing cytokine that has a role in inhibition of arthritis, asthma, and IBD (Behzadi et al., 2016; Bello et al., 2018).