CD40 Ligand Is Increased in Mast Cells in Psoriasis and Actinic Keratosis but Less So in Epithelial Skin Carcinomas.

The expression of CD40 ligand (CD40L) in mast cells was investigated in biopsies from lesional and non-lesional skin samples of patients with psoriasis, actinic keratosis (AK), basal cell carcinoma, and squamous cell carcinoma using a sequential double-staining technique. The percentage of CD40L mast cells was higher in the lesional than in the non-lesional skin (p < .003).

Mast cell chymase in experimentally induced psoriasis.

Mast cell chymase can have a pro-inflammatory or an immunosuppressive function in psoriasis, but the outcome may depend on the level of chymase activity. Therefore, mast cells showing chymase activity (Chyact ) and immunoreactivity (Chyprot ) were studied during the Köbner reaction (0 days, 2 h, 1 day, 3 days and 7 days) of psoriasis induced by the tape-stripping technique. Also, the effect of recombinant human chymase (rh-chymase) or human LAD2 mast cells (LAD2) on the (3) H-thymidine uptake of psoriatic peripheral blood mononuclear cells (PBMC) or total T cells was studied.

Epidermal Expression of Filaggrin/Profilaggrin Is Decreased in Atopic Dermatitis: Reverse Association With Mast Cell Tryptase and IL-6 but Not With Clinical Severity.

Background: A decrease in filaggrin expression contributes to the pathogenesis of atopic dermatitis (AD) and can be modified by inflammatory factors.

Objectives: The aim of this study was to determine the correlation of (pro)filaggrin (filaggrin and profilaggrin) expression with clinical severity in AD and with mast cell (MC) tryptase, chymase, and IL-6.

Methods: Punch biopsies were collected from 17 patients with moderate-to-severe AD and from 10 psoriatic patients.

Experimentally induced psoriatic lesions associate with rapid but transient decrease in interleukin-33 immunostaining in epidermis.

A slight epidermal damage can induce the Köbner reaction in psoriasis, and the “alarmin”, interleukin-33 (IL-33), may be involved in this process. Therefore, the uninvolved psoriatic skin was tape-stripped, and skin biopsies were collected at 0 day, 2 h and 3 days or at 0 day, 1 day and 7 days for immunohistochemistry. Eight patients out of 18 with the positive Köbner reaction showed a decrease in epidermal thickness and revealed transient reduction in epidermal nuclear immunostaining of IL-33 in 2-h, 1-day, 3-day biopsies compared to the 10 Köbner-negative patients.

Is there a role for mast cells in psoriasis?

Mast cells have traditionally been considered as effector cells in allergy but during the last decade it has been realized that mast cells are essentially involved in the mechanisms of innate and acquired immunity. Upon activation by anaphylactic, piecemeal degranulation or degranulation-independent mechanisms mast cells can secrete rapidly or slowly a number of soluble mediators, such as serine proteinases, histamine, lipid-derived mediators, cytokines, chemokines and growth factors. Mast cells can express cell surface co-stimulatory receptors and ligands, and they can express MHC class II molecules and thereby present antigens.