Study of phenotype and dynamic of T-cell mediated antifungal immune in the skin

BECCACECE, IGNACIO; BURSTEIN VL; GUASCONI, LORENA; ALMEIDA, MARIEL; MENA, CRISTIAN J.; CERVI L; PRINZ I; GRUPPI A; CHIAPELLO L S

Córdoba

Congreso; 19th Meeting of Expert in Clinical Mycology-INFOCUS 2021; 2021

INFOCUS Latam ISHAM Working Group y Círculo Médico de Córdoba

The skin is a physical barrier with a dynamic resident immune system that is crucial to control infection, resolve damage or maintain tissue homeostasis. In the last few years it has been discovered that tissue-resident T lymphocytes play a central role in the immunity against pathogens in barrier organs. Dermatophytes are a highly prevalent cause of human disease worldwide, however, the phenotype and dynamic of skin immune cell subsets controlling dermatophyte infection remains poorly understood.We have previously demonstrated that IL-17-mediated immunity (IL-17A and IL-17F) is important in controlling fungal overgrowth in the skin in an experimental model of dermatophytosis in C57BL/6 mice (Microsporum canis or Nannizzia gypsea epicutaneous infection). In this study, we aimed to investigate the immune cell subsets that produce IL-17A in the skin and the role of tissue-resident cells in the antifungal immunity during experimental dermatophytosis with N. gypsea.By employing transgenic IL-17A-GFP-reporter mice and flow cytometry (FC) analysis of epidermal cell suspensions, we observed a significant increase in the frequency of IL-17A-producing CD45+CD3+ T cells at 6 and 8 days of N. gypsea infection in back skin, compared to saline-treated mice (uninfected control, P<0.0001). We demonstrated that IL-17A in the skin is mainly produced by two distinct populations of leukocytes: conventional βTCR+ and γδTCR-expressing (T) CD3+ T cells.To study the in vivo role of γδT cells in the anti-dermatophytic response we infected TCRd-GDL transgenic mice, which can be depleted of γδT cells by diphtheria toxin treatment. After N. gypsea infection (8dpi), γδT-depleted mice showed similar levels of skin fungal burden and IL-17-producing CD45+ skin cell frequency compared to γδT-competent infected controls. In addition, IL-17A production in γδT-depleted animals is produced not only by CD45+CD3+βTCR+ T lymphocytes but also by CD45+CD3- leukocytes after N. gypsea infection suggesting that, in the abscence of γδT cells, IL-17A production is compensated by different cell populations in the skin.We also investigated the role of skin resident T cells by treating IL-17A-GFP-mice with Fingolimod (FTY720, 2μg/g, intraperitoneal daily dose), a drug that prevents the egress of lymphocytes from skin-draining lymph nodes (sdLNs). Flow cytometry analysis revealed that infected FTY-treated mice showed a diminished number of βTCR+ T cells infiltrating the skin compared to infected untreated animals (P<0.05). However, infected FTY-treated mice maintained a subset of skin resident βTCR+ T and T cells (CD103+CD69+ T cells) that produced IL-17A after infection. Furthermore, no differences in the skin fungal burden were observed between FTY-treated vs. untreated mice, suggesting that skin resident IL-17A-producing βTCR+ T and T cells are sufficient to control dermatophyte infection in a context of impaired influx of T lymphocytes from sdLNs.Taking together, these data provides new insights about the dynamic of the skin-specific antifungal T cell-mediated response in dermatophytosis showing that IL-17A cytokine is produced by conventional migratory and resident βTCR+ T and T cell. However, the antifungal immunity in the skin is conserved in the absence of T cell or migratory lymphocytes from skin-draining lymph nodes.