Identification of CD49a+ CD8+ resident memory T cells in vitiligo-like lesions associated with nivolumab treatment for melanoma

Tissue-Resident Memory T Cells in Skin Diseases: A Systematic Review

In health, the non-recirculating nature and long-term persistence of tissue-resident memory T cells (TRMs) in tissues protects against invading pathogens. In disease, pathogenic TRMs contribute to the recurring traits of many skin diseases. We aimed to conduct a systematic literature review on the current understanding of the role of TRMs in skin diseases and identify gaps as well as future research paths. EMBASE, PubMed, SCOPUS, Web of Science, Clinicaltrials.gov and WHO Trials Registry were searched systematically for relevant studies from their inception to October 2020. Included studies were reviewed independently by two authors. This study was conducted in accordance with the PRISMA-S guidelines. This protocol was registered with the PROSPERO database (ref: CRD42020206416). We identified 96 studies meeting the inclusion criteria. TRMs have mostly been investigated in murine skin and in relation to infectious skin diseases. Pathogenic TRMs have been characterized in various skin diseases including psoriasis, vitiligo and cutaneous T-cell lymphoma. Studies are needed to discover biomarkers that may delineate TRMs poised for pathogenic activity in skin diseases and establish to which extent TRMs are contingent on the local skin microenvironment. Additionally, future studies may investigate the effects of current treatments on the persistence of pathogenic TRMs in human skin.

Resident Memory T Cells in Autoimmune Skin Diseases

Tissue resident memory T cells (TRM) are a critical component of the immune system, providing the body with an immediate and highly specific response against pathogens re-infecting peripheral tissues. More recently, however, it has been demonstrated that TRM cells also form during autoimmunity. TRM mediated autoimmune diseases are particularly destructive, because unlike foreign antigens, the self-antigens are never cleared, continuously activating self-reactive TRM T cells. In this article, we will focus on how TRMs mediate disease in autoimmune skin conditions, specifically vitiligo, psoriasis, cutaneous lupus erythematosus, alopecia areata and frontal fibrosing alopecia.

Vitiligo and Melanoma-Associated Vitiligo: Understanding Their Similarities and Differences

BACKGROUND

There has been a significant increase in the number and efficacy of therapies for advanced melanoma. Immunotherapies, such as anti-cytotoxic T-lymphocyte antigen-4 and programmed cell death-1 inhibitors, have improved the prognosis for patients with advanced melanoma. While spontaneous melanoma-associated vitiligo is a known phenomenon, the occurrence of melanoma-associated vitiligo following melanoma therapy is now recognized to associate with favorable outcomes.

OBJECTIVE

The objective of this article is to provide a comprehensive literature review of melanoma-associated vitiligo and explore the insights these findings provide about the pathobiology of vitiligo and mechanisms underlying melanoma therapies.

METHODS

PubMed and Science Direct databases were searched for studies pertaining to melanoma-associated vitiligo. The 36 studies reviewed included meta-analyses (n = 2), prospective cohort studies (n = 4), prospective observational studies (n = 3), retrospective studies (n = 12), case series (n = 2), and case reports (n = 13).

RESULTS

The basic mechanisms underlying melanoma-associated vitiligo and vitiligo may be shared. Characterization of these mechanisms will identify new biomarkers and therapeutic targets for both melanoma and vitiligo.

CONCLUSIONS

Co-opting the immune system to target tumor antigens highlights the potential overlap between anti-tumor immunity and autoimmunity. The development of vitiligo-like depigmentation in association with immunotherapy for melanoma may provide insights into both the immune response against melanoma as well as the pathogenesis of vitiligo.