Allergen sensitization stratifies IL-31 production by memory T cells in atopic dermatitis patients

Leveraging tissue-resident memory T cells for non-invasive immune monitoring via microneedle skin patches

Detecting antigen-specific lymphocytes is crucial for immune monitoring in the setting of vaccination, infectious disease, cancer, and autoimmunity. However, their low frequency and dispersed distribution across lymphoid organs, peripheral tissues, and blood pose challenges for reliable detection. To address this issue, we developed a strategy exploiting the functions of tissue-resident memory T cells (TRMs) to concentrate target circulating immune cells in the skin and then sample these cells non-invasively using a microneedle (MN) skin patch. TRMs were first induced at a selected skin site through initial sensitization with a selected antigen. Subsequently, these TRMs were restimulated by intradermal inoculation of a small quantity of the same antigen to trigger the "alarm" and immune recruitment functions of these cells, leading to accumulation of antigen-specific T cells from the circulation over several days. In mouse models of vaccination, we show that application of MN patches coated with an optimized hydrogel layer for cell and fluid sampling to this skin site allowed effective isolation of thousands of live antigen-specific lymphocytes as well as innate immune cells. In a human subject with allergic contact dermatitis, stimulation of TRMs with allergen followed by MN patch application allowed the recovery of diverse lymphocyte populations that were absent from untreated skin sites. These results suggest that TRM restimulation coupled with microneedle patch sampling can be used to obtain a window into both local and systemic antigen-specific immune cell populations in a noninvasive manner that could be readily applied to a wide range of disease or vaccination settings.

Heterogeneous IL-9 Production by Circulating Skin-Tropic and Extracutaneous Memory T Cells in Atopic Dermatitis Patients

Interleukin (IL)-9 is present in atopic dermatitis (AD) lesions and is considered to be mainly produced by skin-homing T cells expressing the cutaneous lymphocyte-associated antigen (CLA). However, its induction by AD-associated triggers remains unexplored. Circulating skin-tropic CLA+ and extracutaneous/systemic CLA- memory T cells cocultured with autologous lesional epidermal cells from AD patients were activated with house dust mite (HDM) and staphylococcal enterotoxin B (SEB). Levels of AD-related mediators in response to both stimuli were measured in supernatants, and the cytokine response was associated with different clinical characteristics. Both HDM and SEB triggered heterogeneous IL-9 production by CLA+ and CLA- T cells in a clinically homogenous group of AD patients, which enabled patient stratification into IL-9 producers and non-producers, with the former group exhibiting heightened HDM-specific and total IgE levels. Upon allergen exposure, IL-9 production depended on the contribution of epidermal cells and class II-mediated presentation; it was the greatest cytokine produced and correlated with HDM-specific IgE levels, whereas SEB mildly induced its release. This study demonstrates that both skin-tropic and extracutaneous memory T cells produce IL-9 and suggests that the degree of allergen sensitization reflects the varied IL-9 responses in vitro, which may allow for patient stratification in a clinically homogenous population.

CLA+ memory T cells in atopic dermatitis

Circulating skin-homing cutaneous lymphocyte-associated antigen (CLA)+ T cells constitute a small subset of human memory T cells involved in several aspects of atopic dermatitis: Staphylococcus aureus related mechanisms, the abnormal Th2 immune response, biomarkers, clinical aspects of the patients, pruritus, and the mechanism of action of targeted therapies. Superantigens, IL-13, IL-31, pruritus, CCL17 and early effects on dupilumab-treated patients have in common that they are associated with the CLA+ T cell mechanisms in atopic dermatitis patients. The function of CLA+ T cells corresponds with the role of T cells belonging to the skin-associated lymphoid tissue and could be a reason why they reflect different mechanisms of atopic dermatitis and many other T cell mediated skin diseases. The goal of this review is to gather all this translational information of atopic dermatitis pathology.

Itch: from the skin to the brain - peripheral and central neural sensitization in chronic itch

Similar to chronic pain, chronic itch is frequently linked to neural sensitization, a phenomenon wherein the nervous system becomes hypersensitive to stimuli. This process of neural sensitization of chronic itch is orchestrated by various signaling pathways and mediators in both the peripheral and central nervous systems. At the level of the peripheral nervous system, inflammation and neuroimmune interactions induce plastic changes to peripheral nerve fibers, thereby amplifying the transmission of itch signaling. Neural sensitization in the central nervous system occurs at both the spinal cord and brain levels. At the level of the spinal cord, it involves hyperactivity of itch-activating spinal pathways, dysfunction of spinal inhibitory circuits, and attenuation of descending supraspinal inhibitory pathways. In the brain, neural sensitization manifests as structural and functional changes to itch-associated brain areas and networks. Currently, we have a diverse array of neuroimmune-modulating therapies targeting itch neural sensitization mechanisms to help with providing relief to patients with chronic itch. Itch research is a dynamic and continually evolving field, and as we grow in our understanding of chronic itch mechanisms, so will our therapeutic toolbox. Further studies exploring the peripheral and central neural sensitization mechanisms in the context of chronic itch are needed.