Abstract Background Autoantibodies targeting the endothelial protein C receptor (EPCR) have been identified in ulcerative colitis (UC) and represent a novel predictive and diagnostic tool. Since the antigen presents a naturally bound phospholipid, we aimed to assess a potential role of EPCR lipidation on the detection of anti-EPCR antibodies in inflammatory bowel disease (IBD). Methods To this end, serum samples from patients with UC, Crohns disease, and healthy controls were analyzed using an in-house ELISA employing either lipidated or delipidated recombinant EPCR. Results Overall, male UC patients showed significantly higher absorbance (mean = 1.09) than CD patients (mean = 0.50) and controls (mean = 0.37). Remarkably, in males, the difference between UC patients and controls was highly significant (p = 1.2e-07), as was the difference between UC and CD patients (p = 5.7e-05). In women, while UC patients showed higher absorbance (mean = 0.71) than controls (mean = 0.45), the difference was less pronounced and only significant when comparing UC to controls (p = 0.023). Replacement of native EPCR with delipidated EPCR in the ELISA procedure dropped detection and eliminated the UC-CD discrimination power (p = 0.784). Conclusion These findings indicate a role for the bound lipid as key determinant of male-biased, anti-EPCR reactivity, and support the diagnostic potential of this biomarker when assay conditions preserve the physiological lipid-bound state of EPCR. References: 1. Mutoh T, Shirai T, Ishii T, et al. Identification of two major autoantigens negatively regulating endothelial activation in Takayasu arteritis. Nat Commun 2020;11:1253.5. 2. Kakuta Y, Shirai T, McGovern DPB, et al. Novel Diagnostic Autoantibodies Against Endothelial Protein C Receptor in Patients With Ulcerative Colitis. Clinical Gastroenterology and Hepatology 2023;21:844–846.6. 3. Erausquin E, Morán-Garrido M, Sáiz J, et al. Identification of a broad lipid repertoire associated to the endothelial cell protein C receptor (EPCR). Sci Rep 2022;12:15127.9. 4. Lopez-Sagaseta J, Puy C, Tamayo I, et al. sPLA2-V inhibits EPCR anticoagulant and antiapoptotic properties by accommodating lysophosphatidylcholine or PAF in the hydrophobic groove. Blood 2012;119:2914–2921.10. Conflict of interest: Dr. López-Sagaseta, Jacinto: I am inventor and I declare that a patent application has been filed concerning a ELISA method for detecting anti-EPCR autoantibodies recognizing both lipid-dependent and lipid-independent epitopes. Ugidos-Damboriena, Nerea: Nerea Ugidos-Damboriena is listed as an inventor on a patent related to the work described, but holds no ownership or financial interest. Jaime-Gomez, Llucia: Llucia Jaime Gomez is inventor and holds ownership on a patent application concerning the ELISA method described in this study for detecting anti-EPCR autoantibodies recognizing both lipid-dependent and lipid-independent epitopes Rodríguez Gutiérrez, Cristina: Cristina Rodriguez Gutierrez declares no conflicts of interest Lucia, Zabalza Sanmartin: Lucia Zabalza Sanmartin declares no conflicts of interest Nantes Castillejo, Oscar: Oscar Nantes declares no conflicts of interest Dichiara Rodriguez, Maria Gilda: Maria Gilda Dichiara Rodriguez is inventor and holds ownership on a patent application concerning the ELISA method described in this study for detecting anti-EPCR autoantibodies recognizing both lipid-dependent and lipid-independent epitopes
López-Sagaseta et al. (Thu,) studied this question.