Introduction

Diagnosis of celiac disease (CeD) is dependent on serological markers like IgA antibodies against transglutaminase 2 (TG2) and IgG antibodies against deamidated gluten peptides (DGP) caused by dietary gluten. The underlying immunological drivers of antibody response are however still poorly characterized. Clarifying these drivers may improve serology-based diagnostics and offer valuable immunobiological insight for CeD.

Aims & Methods

In this project, we aimed to identify new serum factors that are associated with celiac disease and serological response. A total of 224 serum samples (161 untreated and 63 treated) from patients with CeD were selected from Oslo University Hospital’s Intestinal Disease Biobank collected between 2018 to 2024. Data on serological response and treatment status were collected and the samples were compared with 40 healthy individuals. Serum samples from treated CeD were paired samples of untreated CeD. Serum was analyzed using the Olink® Target 96 Inflammation panel, which uses PCR-amplified dual-antibody proximity extension. Analyses were performed at the Proteomic Core Facility at Oslo University Hospital and statistics were performed in R-based with the OlinkAnalyze package.

Results

Thirty-one proteins differed significantly across all comparisons (p < 0.05) and were more abundant in CeD than in healthy controls. When untreated CeD was compared with controls, 24 proteins were elevated, namely CXCL9, CXCL10, CXCL11 (all ligands for CXCR3), CCL25 (ligand for CCR9), IFN-gamma, IL12B, IL17A, IL7, IL8, IL10, IL15RA, LIF, CCL11, CCL20, CCL28, PD-L1, TNFRSF9, CD40, VEGFA, ARTN, MMP10, ADA, ST1A1 and STAMBP. In treated CeD, 9 proteins were elevated compared to controls, namely CXCL10, CXCL11, IL12B, IL7, CD40, TNFRSF9, CSF1, VEGFA and ST1A1. Paired comparisons of treated and untreated samples showed that CXCL9, CXCL11, CCL11, CCL25, IL17A, TNFRSF9 and ADA were significantly higher in the untreated group. The proteins CXCL11 and TNFRSF9 were significant in all 3 comparisons. No significant differences were noted when comparing IgA-TG2 and IgG-DGP responses; however, IL-17A and CXCL11 were significantly lower among those with only a TG2 response compared to double positives.

Conclusion

We here report that multiple serum proteins are significantly elevated in untreated and treated CeD patients compared to healthy individuals. Many of the same serum proteins have previously been reported in serum taken hours after gluten challenge. Of particular interest, IL7, which is upregulated in intestinal CeD mucosa, was significantly upregulated in serum compared to controls. Both CXCL11 and TNFRSF9 which were found to be significant in all comparisons are immunological proteins relevant for T-cell activation and regulations. Future analyses will incorporate clinical data, including Marsh grades and serological levels, to deepen our understanding of the immunological landscape in CeD.