CXCR5 and systemic lupus erythematosus: The analysis of methylation levels at the CXCR5 cg19599951 locus across the different groups indicated median methylation levels of 0.817 (interquartile range [IQR]: 0.781–0.841) in HC, 0.839 (IQR: 0.814–0.868) in RA, 0.811 (IQR: 0.788–0.844) in AS, 0.864 (IQR: 0.811–0.900) in SLE, 0.834 (IQR: 0.802–0.850) in PsA, and 0.816 (IQR: 0.784–0.883) in SS.