Eccrine Sweat as a Biofluid for Profiling Immune Biomarkers

Purpose Experimental Design 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. 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-1 alpha (n = 16), epidermal growth factor (n = 6), and angiogenin (n = 7). Results Conclusions and Clinical Relevance 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-1 alpha 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. Sweat can be used for profiling antibodies and innate immune biomarkers.