{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,1]],"date-time":"2026-06-01T22:58:48Z","timestamp":1780354728168,"version":"3.54.1"},"reference-count":38,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,5,18]],"date-time":"2026-05-18T00:00:00Z","timestamp":1779062400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Immunol."],"abstract":"<jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>Psoriatic arthritis (PsA) often requires escalation from conventional synthetic disease-modifying antirheumatic drugs (csDMARDs) to biologic therapy (bDMARDs), yet biomarkers guiding treatment decisions remain limited. Anti-CD74 autoantibodies have shown diagnostic potential in axial spondyloarthritis, but their relevance in PsA is insufficiently characterized.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Objective<\/jats:title>\n                    <jats:p>To evaluate whether IgA anti-CD74 levels are associated with treatment escalation in peripheral PsA (pPsA) and to characterize their relationships with clinical and immunological parameters.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>Serum samples from 171 PsA (127 pPsA, 44 axial PsA [axPsA]), 43 non-rheumatic disease controls (NRD), and 43 rheumatoid arthritis (RA) patients were analyzed. IgA anti-CD74 levels were measured by enzyme-linked immunosorbent assay (ELISA). Patients were stratified by disease duration and treatment exposure. Correlation analyses, receiver operating characteristic (ROC) curves, and logistic regression models were performed. A prospective subgroup of 53 early pPsA patients was followed to assess treatment initiation.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>IgA anti-CD74 levels were elevated in PsA compared with NRD controls (median 13 vs. 6 U\/mL, p &amp;lt; 0.0001), with similar levels in pPsA and axPsA and comparable values in RA, indicating an association with inflammatory disease rather than disease specificity. Anti-CD74 positivity (&amp;gt;15 U\/mL) was observed in 31.5% of pPsA and 43.2% of axPsA versus 2.3% of NRD, independent of disease duration. Anti-CD74 levels were associated with treatment escalation in pPsA, with higher levels in bDMARD-treated patients (median 13.0 vs. 11.0 U\/mL, p = 0.04). In multivariate analyses, anti-CD74 was independently associated with csDMARD (OR 1.113, p = 0.022) and bDMARD use (OR 1.052, p = 0.02). After false discovery rate (FDR) correction, anti-CD74 remained associated with serum IgA (q = 0.0008) and weakly with IgG (q = 0.0250), but not with C-reactive protein (CRP) or age. Longitudinal associations were not significant after FDR correction (csDMARD initiation: p = 0.047, q = 0.094; bDMARD initiation: p = 0.19, q = 0.1866), indicating these findings are exploratory.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusion<\/jats:title>\n                    <jats:p>IgA anti-CD74 levels are elevated in PsA and appear to reflect immunological activity not captured by CRP. Their independent association with treatment escalation in pPsA supports further evaluation as a biomarker candidate, although findings remain exploratory and require validation in larger longitudinal cohorts.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.3389\/fimmu.2026.1821206","type":"journal-article","created":{"date-parts":[[2026,5,18]],"date-time":"2026-05-18T05:42:43Z","timestamp":1779082963000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["IgA anti-CD74 autoantibodies are associated with treatment escalation in peripheral psoriatic arthritis"],"prefix":"10.3389","volume":"17","author":[{"given":"Alaa","family":"Elsaghir","sequence":"first","affiliation":[{"name":"Department of Rheumatology and Immunology, Hannover Medical School","place":["Hannover, Germany"]},{"name":"Department of Microbiology & Immunology, Faculty of Pharmacy, Assiut University","place":["Assiut, 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