Immunology: Worm-activated immunity may suppress arthritis

Activation of a specific immune response triggered by parasitic worm infections can help to treat rheumatoid arthritis in mice, reports a study in Nature Communications this week.

Rheumatoid arthritis is an autoimmune disease of the joints. The immune responses responsible for this disease - Th1 and Th17 responses - have evolved to fight bacteria and viruses, but in arthritis they instead attack cartilage, causing tissue damage, inflammation and pain. Little is known about the immune mechanisms counteracting inflammation in rheumatoid arthritis, and the link between worm infections and arthritis had not been established until now.

Aline Bozec and colleagues induce arthritis in mice (groups of 3-11 across several experiments) and infect a subset with parasitic worms (Nippostrongylus brasiliensis) in order to study their immune responses. They compare infected mice with control groups and find that worm infections protect mice from arthritis and that this protection is mediated by a specific type of immune response known as Type 2 (Th2), which is activated by the worms. The Th2 response is responsible for expelling the worms from the mice, and in addition it promotes tissue repair and inhibits inflammation, efficiently counteracting the arthritis-causing Th1 and Th17 immune responses. The authors also find that the cellular components of the Th2 responses are present in samples of knee joint tissue from 20 patients suffering from arthritis, suggesting that even in the absence of worm infection these responses are already engaged in suppressing the pathology.

These results suggest that activating the Th2 immune response by using vaccine-like stimuli could pave the way for the development of new treatments for arthritis in humans.