Pain-induced skin autoimmunity

The nerve injuries attenuate the persistence of psoriatic lesions

BACKGROUND

The involvement of the nerve in psoriasis development was suggested by sporadic case reports.

OBJECTIVES

To provide multiple evidence for the nerve in psoriasis development with a retrospective case review, a literature review and a mouse-based experimental experiment.

METHODS

Psoriatic patients who had concomitant nerve injuries and such cases from literatures were reviewed. And, on wild-type mouse level, unilateral denervation surgery was performed on the dorsal skin before and after the induction of psoriasiform dermatitis, respectively. Lesion visual scores were calculated, and biopsies were taken for hematoxylin-eosin (HE) staining, immunofluorescence analysis, and RNA sequencing & bioinformatics analysis before denervation surgery and the 2^nd, 4^th, 6^th, 8^th day after the surgery.

RESULTS

All clinical cases (20/20) showed that local lesions under the control of injured nerves relieved spontaneously or even cleared/spared, and only about 1/3 experienced partial recurrence. Next, mouse psoriasiform experiments demonstrated that unilateral denervation prior to imiquimod application attenuated the enhancement of inflammatory reactions (e.g. adaptive immune response and Th17 cell differentiation pathway) and the induction of ipsilateral psoriasiform dermatitis. On the other hand, unilateral denervation after psoriasiform dermatitis induction promoted the regression of inflammatory reactions (e.g. T cell activation, TNF signaling, and Th17 cell differentiation pathway) and ipsilateral dermatitis recovery.

CONCLUSION

Our study based on both retrospective clinical case review and wild-type mouse experiments provides multiple evidence for the involvement of the nerve in psoriasis development. Regulation of immune events, including TNF signaling and Th17 cell differentiation, may be the mechanisms of the nerve in psoriasis.

Organization of the Skin Immune System and Compartmentalized Immune Responses in Infectious Diseases

The skin is an organ harboring several types of immune cells that participate in innate and adaptive immune responses. The immune system of the skin comprises both skin cells and professional immune cells that together constitute what is designated skin-associated lymphoid tissue (SALT). In this review, I extensively discuss the organization of SALT and the mechanisms involved in its responses to infectious diseases of the skin and mucosa. The nature of these SALT responses, and the cellular mediators involved, often determines the clinical course of such infections. I list and describe the components of innate immunity, such as the roles of the keratinocyte barrier and of inflammatory and natural killer cells. I also examine the mechanisms involved in adaptive immune responses, with emphasis on new cytokine profiles, and the role of cell death phenomena in host-pathogen interactions and control of the immune responses to infectious agents. Finally, I highlight the importance of studying SALT in order to better understand host-pathogen relationships involving the skin and detail future directions in the immunological investigation of this organ, especially in light of recent findings regarding the skin immune system.