DEFB1 and systemic sclerosis: In contrast, β-defensin 1 (DEFB1), an AMP produced by epithelial cells, is expressed across all samples; however, these levels are significantly lower is SSc lesional skin compared to healthy controls (p < 0.001 by unpaired t-test), as well as in lesional forearm compared to non-lesional back skin (p = 0.007 by paired t-test) (Additional file 3: Table S3).