Study of plasma anti-CD26 autoantibody levels in a cohort of treatment-naïve early arthritis patients

Abstract

In rheumatoid arthritis (RA), the identifcation of biomarkers to adjust treatment intensity and to correctly diagnose the disease in early stages still constitutes a challenge and, as such, novel biomarkers are needed. We proposed that autoantibodies (aAbs) against CD26 (DPP4) might have both etiological importance and clinical value. Here, we perform a prospective study of the potential diagnostic power of Anti-CD26 aAbs through their quantifcation in plasmas from 106 treatment-naïve early and undiferentiated AR. Clinical antibodies, Anti-CD26 aAbs, and other disease-related biomarkers were measured in plasmas obtained in the frst visit from patients, which were later classifed as RA and non-RA according to the American College of Rheumatology criteria. Two diferent isotype signatures were found among ten groups of patients, one for AntiCD26 IgA and other for Anti-CD26 IgG and IgM isotypes, both converging in patients with arthritis (RA and Unresolved Undiferentiated Arthritis: UUA), who present elevated levels of all three isotypes. The four UUA patients, unresolved after two years, were ACPA and rheumatic factor (RF) negatives. In the whole cohort, 51.3% of ACPA/RF seronegatives were Anti-CD26 positives, and a similar frequency was observed in the seropositive RA patients. Only weak associations of the three isotypes with ESR, CRP and disease activity parameters were observed. Anti-CD26 aAbs are present in treatmentnaïve early arthritis patients, including ACPA and RF seronegative individuals, suggestive of a potential pathogenic and/or biomarker role of Anti-CD26 aAbs in the development of rheumatic diseases