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.