Neuroimmune mechanisms in patients with atopic dermatitis during chronic stress

Objective To identify pathoaetiological neuroimmune mechanisms in patients with atopic dermatitis (AD) and chronic stress, focusing at nerve density, sensory neuropeptides, and the serotonergic system. Methods Eleven patients with AD with histories of stress worsening were included. Biopsies from involved and non‐involved skin were processed for immunohistochemistry. Salivary cortisol test was done as a marker for chronic stress. Results There were more acanthosis and fewer nerve fibres in epidermis and papillary dermis of involved compared with non‐involved skin. Whereas there was no significant change in the number of substance P and calcitonin gene‐related peptide–positive nerve fibres between the involved and non‐involved skin, there was an increase in the epidermal fraction of 5‐hydroxtrytamine 1A (5‐HT1A) receptor and serotonin transporter protein (SERT) immunoreactivity in the involved skin. The number of 5‐HT2AR, CD3‐positive cells, and SERT‐positive cells, most of them being CD3 positive, was increased in involved skin. There was an increase in mast cells in the involved skin, and these cells were often located close to the basement membrane. There was a strong tendency to a correlation between 5‐HT2AR positive cells in the papillary dermis of involved skin and low cortisol ratios, being an indicator of chronic stress. Conclusion A changed innervation and modulation of the serotonergic system are indicated in chronic atopic eczema also during chronic stress.