Strikingly, 50% from the ACPA/RF double negative RA patients showed high levels of Anti-CD26 aAbs

Strikingly, 50% from the ACPA/RF double negative RA patients showed high levels of Anti-CD26 aAbs. 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 treatment-na?ve early arthritis patients, including ACPA and RF seronegative individuals, suggestive of a potential pathogenic and/or biomarker role of Anti-CD26 aAbs in the BEC HCl development of rheumatic diseases. test or the non-parametric MannCWhitney test. The ANOVA or KruskalCWallis test was carried out to compare the variables among more than two groups. Pearsons correlation was used to evaluate the strength of the linear relationship between the measured variables. Statistical analyses were carried out with the software SPSS version 20 (SPSS, Chicago IL, USA). Results Anti-CD26 aAbs of Several Isotypes are Found in Plasma of Healthy Donors and Treatment-Na?ve Early Arthritis Patients To assess whether Anti-CD26 aAbs were present at baseline in early, treatment-na?ve, arthritis patients, we quantified the Ievels of all main isotypes of Anti-CD26 aAbs (IgA, IgG and IgM) in 106 patients at their first visit to the early arthritis clinic. These patients were followed for two years, and in this period a diagnosis was done for all of them. We categorized the patients in ten groups (see Subjects and Methods section and Table ?Table1),1), based upon their diagnosis after the two-year follow-up period, following the 1987 ACR classification criteria (Regueiro et al. 2017). We also quantified BEC HCl the Anti-CD26 aAbs levels in a cohort of 45 healthy donors. Table 1 Anti-CD26/DPP4 autoantibody levels in plasma of the healthy donor cohort and drug-na?ve early arthritis patients ankylosing spondylitis, chondrocalcinosis/gout, early arthritis, healthy donor, mechanic pathology, palindromic rheumatism, post-infectious arthritis, polymyalgia rheumatic, psoriatic arthritis, rheumatoid arthritis, related inflammatory processes, resolved undifferentiated arthritis, systemic lupus erythematosus, unresolved undifferentiated arthritis We found that all the healthy donors present Anti-CD26 aAbs of one isotype or another, with 100% of them having IgG and IgM Anti-CD26 aAbs, HOX11L-PEN and 77.7% also having IgA Anti-CD26 aAbs, albeit at lower titers (Table ?(Table1).1). IgM Anti-CD26 aAb levels are similar to those found in serum in our previous studies, while IgG and, particularly, IgA levels are lower than those in serum (Cordero et al. 2017; De Chiara et al. 2020). In the case BEC HCl of the IgA isotype, all groups of patients present higher levels of Anti-CD26 aAbs than healthy donors (Table ?(Table11 and Fig.?1), with the highest values found in RA and CG patients; in these two groups of patients, IgA Anti-CD26 aAbs values were around 5- and tenfold higher than those of the other patient groups and healthy donors, respectively. Interestingly, IgG and IgM values in CG patients were the lowest of all the groups, including healthy donors, suggesting a specific Anti-CD26 IgA-specific response in CG. Open in a separate window Fig. 1 Anti-CD26/DPP4 autoantibody levels in plasma of the healthy donor cohort and drug-na?ve early arthritis patients. Values in bars represent median SD of arbitrary absorbance models: (1) rheumatoid arthritis?+?palindromic rheumatism?+?PMR: polymyalgia rheumatica; (2) unresolved undifferentiated arthritis; (3) resolved undifferentiated arthritis; (4) related inflammatory processes; (5) systemic lupus erythematosus; (6) chondrocalcinosis/gout; (7) ankylosing spondylitis; (8) psoriatic arthritis; (9) mechanic pathology; (10) post-infectious arthritis; (C) healthy donor With respect to the other patient groups, IgG and BEC HCl BEC HCl IgM Anti-CD26 aAb levels were correlated, as expected. The highest median levels were found in UUA and PIA patients, with RA, RUA, SLE, AS and PsA showing intermediate levels, and RIP, CG and MP showing low levels. Interestingly, IgM (but not IgG) levels were lower in these three later groups than in healthy donors. In summary, we found that Anti-CD26 aAbs are frequent, but with variable levels depending upon the isotype and the disease status. Anti-CD26/DPP4 Autoantibody Levels in Plasma with Respect to the ACPA and Rheumatic Factor Positivity To try to correlate the presence and titer of Anti-CD26 aAbs and disease status, we measured ACPA and rheumatic factor (RF), two markers that are usually detected only in RA patients and are routinely used as diagnostic tools. As.