Interestingly, much fewer saliva samples from RA patients contained undetectable levels of either IL-2 or IL-4 (6/14 for IL-2 and 4/14 for IL-4) compared to ORD (10/13 and 10/12, respectively) and to HC (10/13 and 7/13, respectively). Here, IL2 is linked to rheumatoid arthritis.