Eccrine Sweat as a Biofluid for Profiling Immune Biomarkers

Purpose: Sweat is a relatively unexplored biofluid for diagnosis and monitoring of disease states. In this study, the proteomic profiling of immune-related biomarkers from healthy individuals are presented. Experimental Design: Eccrine sweat samples are collected from 50 healthy individuals. LC-MS/MS is performed on two pools of sweat samples from five male and female participants. Individual sweat samples are analyzed by antibody isotyping microarrays (n = 49), human cytokine arrays (n = 30), and quantitative ELISAs for interleukin-1α (n = 16), epidermal growth factor (n = 6), and angiogenin (n = 7). Results: In sweat, 220 unique proteins are identified by shotgun analysis. Detectable antibody isotypes include IgA (100% positive; median 1230 ± 28 700 pg mL ⁻¹ ), IgD (18%; 22.0 ± 119 pg mL ⁻¹ ), IgG1 (96%; 1640 ± 6750 pg mL ⁻¹ ), IgG2 (37%; 292 ± 6810 pg mL ⁻¹ ), IgG3 (71%; 74.0 ± 119 pg mL ⁻¹ ), IgG4 (69%; 43.0 ± 42.0 pg mL ⁻¹ ), and IgM (41%; 69.0 ± 1630 pg mL ⁻¹ ). Of 42 cytokines, three are readily detected in all sweat samples (p < 0.01). The median concentration for interleukin-1α is 352 ± 521 pg mL ⁻¹ , epidermal growth factor is 86.5 ± 147 pg mL ⁻¹ , and angiogenin is 38.3 ± 96.3 pg mL ⁻¹ . Multiple other cytokines are detected at lower levels. Conclusions and Clinical Relevance: Sweat can be used for profiling antibodies and innate immune biomarkers.