Evaluation of Stress Systems by Applying Noninvasive Methodologies: Measurements of Neuroimmune Biomarkers in the Sweat, Heart Rate Variability and Salivary Cortisol

The two main arms of the stress system include the autonomic nervous system (ANS) and the hypothalamic-pituitary-adrenal (HPA) axis. These two neural stress systems coordinate the response of many other physiological systems to a stressor, including the immune and cardiovascular systems, bringing the body back to homeostasis. The nervous and immune systems communicate with each other in a bidirectional manner. In this review, we will discuss the use of noninvasive methods to evaluate the immune system, ANS and HPA axis. Collection of sweat and saliva, and measurement of heart rate variability are noninvasive methods that can be applied to evaluate neuroimmune interactions. Recently, we validated a new methodology to simultaneously evaluate a large array of neural and immune biomarkers in sweat, collected through cutaneous sweat patches and measured by recycling immunoaffinity chromatography. Noninvasive and ambulatory methodologies of biomarker collection can overcome several limitations intrinsic to invasive methods, such as reducing the stress triggered by collection itself and allowing a wider application to field and community-based settings. Ultimately, simultaneous evaluation of neural and immune systems with noninvasive techniques will help elucidate the underlying interactions of these systems and their role in disease susceptibility and progression of stress-related disorders.