Immunophenotypic Analysis Reveals Differences in Circulating Immune Cells in the Peripheral Blood of Patients with Segmental and Nonsegmental Vitiligo.

Accumulating studies have indicated immune-based destruction of melanocytes in both segmental vitiligo (SV) and non-SV (NSV). Whereas SV often occurs unilaterally during childhood and stabilizes after an initial period of activity, the disease course of NSV is usually slowly progressive, with new lesions occurring bilaterally during life. This suggests an involvement of distinct pathophysiology pathways, specifically increased systemic immune activation in patients with NSV but not in patients with SV. This research aimed to identify the differences in immune cells in the blood of patients with SV and NSV through immunophenotyping of circulating cells. Regulatory T cells were unaffected in patients with SV compared with that in healthy controls but decreased in patients with NSV. In patients with NSV, the reduction in regulatory T cells was associated with the presence of other systemic autoimmune comorbidities, which were less present in SV. Similarly, the absence of a melanocyte-specific antibody response in patients with SV suggests less involvement of B-cell immunity in SV. These data show that in contrast to patients with NSV, no increased systemic immunity is found in patients with SV, indicating that SV pathogenesis is associated with a localized cytotoxic reaction targeting epidermal melanocytes.

House dust mite allergens Der f and Der p induce IL-31 production by blood-derived T cells from atopic dermatitis patients.

Aero-allergens, such as house dust mite (HDM), have been suggested to play a role in the initiation of atopic dermatitis (AD)-related skin inflammation. Here, we analysed the proliferation and the cytokine expression of blood-derived T cells from AD and healthy individuals upon HDM-allergen stimulation. The proliferating cells from healthy individuals and AD patients had a significantly different, distinct cytokine profile: in AD blood, we found increased frequencies of HDM-reactive IL-31-producing T cells, as well as a decreased Th1/Th2 and Tc1/Tc2 ratio, suggesting that allergen-specific T cells in blood of chronic AD patients are subject to pre-existent Th2-Tc2 and "Th31-Tc31" programming.

The IL-17A-producing CD8+ T-cell population in psoriatic lesional skin comprises mucosa-associated invariant T cells and conventional T cells.

IL-17A is pivotal in the etiology of psoriasis, and CD8(+) T cells with the ability to produce this cytokine (Tc17 cells) are over-represented in psoriatic lesions. Here we demonstrate that the frequency of Tc17 cells in peripheral blood of psoriasis patients correlated with the clinical severity of the disease. Analysis of cutaneous-associated lymphocyte antigen expression showed that the blood Tc17 population contains a significantly higher proportion of cells with skin-homing potential compared with the CD8(+) T-cell population lacking IL-17A/IL-22 expression. IL-17A-producing CD8(+) T cells in blood have previously been reported to belong mainly to the mucosa-associated invariant T-cell (MAIT cell) lineage characterized by TCR Vα7.2 chain, CD161, IL-18Rα, and multidrug transporter ABCB1 expression. We demonstrate the presence of CD8(+) MAIT cells in the dermis and epidermis of psoriatic plaques, as well as healthy skin; however, IL-17A-producing CD8(+) MAIT cells were predominantly found in psoriatic skin. Notably, we observed IL-17A production in a large proportion of psoriatic plaque-derived CD8(+) T cells devoid of MAIT cell characteristics, likely representing conventional CD8(+) T cells. In conclusion, we provide supporting evidence that implicates Tc17 cells in the pathogenesis of psoriasis and describe the presence of innate CD8(+) MAIT cells in psoriatic lesions as an alternative source of IL-17A.