Cutaneous Lymphocyte-associated Antigen Research Articles

Heterogeneous IL-9 Production by Circulating Skin-Tropic and Extracutaneous Memory T Cells in Atopic Dermatitis Patients.

Interleukin (IL)-9 is present in atopic dermatitis (AD) lesions and is considered to be mainly produced by skin-homing T cells expressing the cutaneous lymphocyte-associated antigen (CLA). However, its induction by AD-associated triggers remains unexplored. Circulating skin-tropic CLA+ and extracutaneous/systemic CLA- memory T cells cocultured with autologous lesional epidermal cells from AD patients were activated with house dust mite (HDM) and staphylococcal enterotoxin B (SEB). Levels of AD-related mediators in response to both stimuli were measured in supernatants, and the cytokine response was associated with different clinical characteristics. Both HDM and SEB triggered heterogeneous IL-9 production by CLA+ and CLA- T cells in a clinically homogenous group of AD patients, which enabled patient stratification into IL-9 producers and non-producers, with the former group exhibiting heightened HDM-specific and total IgE levels. Upon allergen exposure, IL-9 production depended on the contribution of epidermal cells and class II-mediated presentation; it was the greatest cytokine produced and correlated with HDM-specific IgE levels, whereas SEB mildly induced its release. This study demonstrates that both skin-tropic and extracutaneous memory T cells produce IL-9 and suggests that the degree of allergen sensitization reflects the varied IL-9 responses in vitro, which may allow for patient stratification in a clinically homogenous population.

Single-cell RNA sequencing reveals the expansion of circulating tissue-homing B cell subsets in secondary acute dengue viral infection

The roles of antibodies secreted by subsets of B cells in dengue virus (DENV) infection have been extensively studied, yet, the contribution of tissue-homing B cells to antiviral immunity remains unclear. In this study, we performed a comprehensive analysis of B cell subpopulations in peripheral blood samples from DENV-infected patients using single-cell RNA-sequencing (scRNA-seq) datasets and flow cytometry. We showed that plasma cells (PCs) and plasmablasts (PBs) were the predominant B cell populations during the acute phase of secondary natural DENV infection, but not in convalescent phase nor in healthy controls. Interestingly, these cells expressed proliferation, adhesion, and tissue-homing genes, including SELPLG, a homing marker of the skin, the initial infected site of DENV. Flow cytometry analysis confirmed a significant upregulation of cell surface expression of a cutaneous lymphocyte-associated antigen (CLA) encoded by SELPLG in PCs and PBs, compared to naive and memory B cells from the same patients. The analysis of an independent single-cell B-cell receptor sequencing (scBCR-seq) dataset of DENV-infected patients revealed that the peripheral blood PCs and PBs exhibited the highest clonal expansion in secondary DENV infection compared to other B cell subsets. These clonally expanded cells also expressed the highest levels of tissue-homing genes, including SELPLG. In addition, by utilizing a public scRNA-seq dataset of SARS-CoV2 infection, we demonstrated the upregulation of several tissue-homing genes in PCs and PBs. Our study provides evidence for the potential roles of tissue-homing B cell subsets in the context of immune responses against viral infections in humans.

CLA+ memory T cells in atopic dermatitis

Circulating skin-homing cutaneous lymphocyte-associated antigen (CLA)+ T cells constitute a small subset of human memory T cells involved in several aspects of atopic dermatitis: Staphylococcus aureus related mechanisms, the abnormal Th2 immune response, biomarkers, clinical aspects of the patients, pruritus, and the mechanism of action of targeted therapies. Superantigens, IL-13, IL-31, pruritus, CCL17 and early effects on dupilumab-treated patients have in common that they are associated with the CLA+ T cell mechanisms in atopic dermatitis patients. The function of CLA+ T cells corresponds with the role of T cells belonging to the skin-associated lymphoid tissue and could be a reason why they reflect different mechanisms of atopic dermatitis and many other T cell mediated skin diseases. The goal of this review is to gather all this translational information of atopic dermatitis pathology.

Distinct Patterns in Treg and T-helper Subset Reconstitution After Autologous Hematopoietic Stem Cell Transplantation in Juvenile-onset Systemic Sclerosis Patients

Systemic sclerosis (SSc) is a refractory autoimmune disease. In recent years, autologous hematopoietic stem cell transplantation (ASCT) has been performed to treat SSc. However, the reconstitution of immune components post-ASCT in SSc have not been fully described.We tested a total of 13 samples from 4 consenting SSc patients (median age: 18.5-years-old, 3F/1M) receiving IRB-approved immunoablation (TBI 600cGy) with lung/kidney shielding and Cytoxan (n = 3) or Thiotepa (n = 1) +/– Alemtuzumab followed by ASCT (CD34+ selected). Peripheral blood samples were collected at baseline, and 3, 6, 12, 24-months post-ASCT. By flow cytometry, we focused on the FOXP3+Treg and T-helper subset reconstitution.All 4 subjects experienced significant improvement in several clinical and quality of life parameters, especially in their skin disease evident within weeks after ASCT. T-cell recovery was evident by 6-months reaching pre-ASCT levels by 2-years post-ASCT (Fig. 1A). There was an increased percentage of FOXP3+Tregs in total CD4+T cells from 3- to 6-months post-ASCT (Fig. 1B), leading to an increase in the ratio of Treg/Tcon (Fig. 1B). The higher proportions of proliferating Tregs (Fig. 1C) likely led to their increased numbers. This trend was sustained until the last evaluation at 2-years post-ASCT (Fig. 1C). In contrast, CD4+Tcons showed a relatively lower proliferation rate, leading to a higher ratio of Ki67+Treg/Ki67+Tcon compared to pre-ASCT values (Fig. 1C). Notably, there was an increased proportion of Tregs expressing the skin-homing marker cutaneous lymphocyte-associated antigen (CLA) at 3-months lasting until the last test at 2-years post-ASCT (Fig. 1D), whereas CLA+/CD4+Tcons were less plentiful.The reconstitutions of T-helper (Th) subsets were also examined according to their chemokine receptor expression. Gradually decreased numbers of Th2, Th9, and Th17 were observed in the peripheral pool (Fig. 1E,1F). Nevertheless, the absolute number of Th1 and Th22 cells returned to levels seen pre-ASCT without any recurrence or flare of SSc symptoms.In summary, an increased number of circulating FOXP3+Tregs was observed leading to an elevated Treg/Tcon ratio in the peripheral pool. Skin-homing CLA+Treg subset was further enriched correlating with improved skin scores in all patients. The decrease of the Th2/Th9/Th17 subsets in the peripheral pool post-ASCT possibly contributes to the clinically less severe autoimmune phenotype. [Display omitted]

Allergen sensitization stratifies IL-31 production by memory T cells in atopic dermatitis patients.

The role of allergen sensitization in IL-31 production by T cells and specifically in the clinical context of atopic dermatitis (AD) has not been characterized. The response to house dust mite (HDM) in purified memory T cells cocultured with epidermal cells from AD patients (n=58) and control subjects (n=11) was evaluated. AD-associated cytokines from culture supernatants, plasma proteins and mRNA expression from cutaneous lesions were assessed and related with the clinical features of the patients. HDM-induced IL-31 production by memory T cells defined two subsets of AD patients according to the presence or absence of IL-31 response. Patients in the IL-31 producing group showed a more inflammatory profile, and increased HDM-specific (sp) and total IgE levels compared to the IL-31 non-producing group. A correlation between IL-31 production and patient's pruritus intensity, plasma CCL27 and periostin was detected. When the same patients were analyzed based on sp IgE and total IgE levels, an increased IL-31 in vitro response, as well as type 2 markers in plasma and cutaneous lesions, was found in patients with sp IgE levels > 100 kUA/L and total IgE levels > 1000 kU/L. The IL-31 response by memory T cells was restricted to the cutaneous lymphocyte-associated antigen (CLA)+ T-cell subset. IgE sensitization to HDM allows stratifying IL-31 production by memory T cells in AD patients and relating it to particular clinical phenotypes of the disease.

053 SEB-induced IL-13 production in CLA+ memory T cells defines Th2 high and Th2 low responders in atopic dermatitis

There is currently no clear in vitro model to study the Th2 status in atopic dermatitis (AD). Staphylococcus aureus, skin-homing cutaneous lymphocyte-associated antigen (CLA)+ memory T cells and IL-13 are key players in AD. Circulating CLA+ memory T cells reflect the cutaneous abnormalities in AD. We have studied the CLA+/- memory T-cell response to staphylococcal enterotoxin B (SEB) when cocultured with autologous lesional epidermal cells from adult non-treated moderate-to-severe AD patients. Also, plasma and mRNA expression from the lesional skin biopsies were analysed.

Distinct Patterns in the Reconstitutions of Treg and T-Helper Subsets after Autologous Hematopoietic Stem Cell Transplantation in Juvenile-Onset Systemic Sclerosis Patients

Systemic sclerosis (SSc) is a refractory autoimmune disease characterized by diffuse fibrosis and vasculopathy affecting the skin, joints, and internal organs. Most immunosuppressive drugs have failed to show long-term benefit in randomized trials. In recent years, autologous hematopoietic stem cell transplantation (ASCT) has been performed to treat multiple sclerosis and SSc, however, the reconstitutions of immune components post-ASCT in SSc have not been fully described. Subjects and Methods: We tested a total of 13 samples from 4 consenting SSc patients (3 females, 1 male) receiving IRB-approved immunoablation (TBI 600cGy) with lung shielding and Cytoxan (n=3) or Thiotepa (n=1) +/- Alemtuzumab followed by autologous CD34+ selected, cryopreserved peripheral blood hematopoietic stem cells transplantation. Their median age was 18.5-years-old (range 15.2- to 21.4-years-old). Peripheral blood samples were collected at baseline pre-ASCT, and 3, 6, 12, 24-months post-ASCT. By flow cytometry, we examined lymphocyte and monocyte subset recovery with additional focus on the FOXP3+Treg and T-helper subset reconstitution. Results and Discussion: All 4 subjects experienced significant improvement in several clinical and quality of life parameters, especially in their skin disease evident within weeks after ASCT. T-cell lymphopenia was profound at 3-months; however, the recovery was evident by 6-months reaching pre-ASCT levels by 2-years post-ASCT (Fig 1A). Natural killer (NK) lymphocytes and monocytes attained the normal values by 3-months and after (Fig 1A). The FOXP3+Tregs that appeared post-ASCT displayed distinct features. There was an increased percentage of FOXP3+Tregs in total CD4+T cells during the early stage (3- to 6-months) post-ASCT (Fig 1B), leading to an increase in the ratio of Treg/Tcon (Fig 1B). The higher proportions of proliferating Tregs as measured by Ki67+FOXP3+CD4+/CD25+/CD127- T cells (Fig 1C) likely led to their increased numbers. This trend was sustained until the last evaluation at 2-years post-ASCT (Fig 1C). In contrast, CD4+Tcons showed a relatively lower proliferation rate, leading to a higher ratio of Ki67+Treg/Ki67+Tcon compared to pre-ASCT values (Fig 1C). Notably, there was an increased proportion of Tregs expressing the skin homing marker cutaneous lymphocyte-associated antigen (CLA) at 3-months lasting until the last test at 2-years post-ASCT (Fig 1D), whereas CLA+/CD4+Tcons were less plentiful. The reconstitutions of T-helper (Th) subsets were also examined. Due to lymphopenia at the early stage post-ASCT, Th subsets were identified according to their chemokine receptor expression (Mahnke et alCytometry 2013;83(5):439-440). Gradually decreased numbers of Th2, Th9, and Th17 were observed in the peripheral pool (Fig 1E) contributing to a decline of their proportions in total CD4+T (Fig 1F). Nevertheless, absolute number of Th1 and Th22 cells returned to levels seen pre-ASCT without any recurrence or flare of SSc symptoms. The CD45RO+ memory phenotype was dominant during the early stages post-ASCT in all subsets (data not shown). Summary: Successful reconstitution of lymphocytes and monocytes post-ASCT was observed in available SSc patients. Post-ASCT circulating FOXP3+Tregs displayed distinct features where the increased number led to an elevated Treg/Tcon ratio in the peripheral pool. Amongst Tregs, the skin homing CLA+ subset was further enriched correlating with improved skin scores in all patients. Improved peripheral proliferation and increased expression of CLA+ Tregs may provide protection from skin disease recurrence despite parallel Tcon reconstitution. The decrease of the Th2/Th9/Th17 subsets in the peripheral pool post-ASCT possibly contributes to the clinically less autoimmune phenotype. These results need to be validated in future patients. Acknowledgements: We thank all participating patients, nurses, physicians, and scientists in this study for their contributions. The study was supported by the "Idea Development Award" from the Department of Defense - Scleroderma Research Program (Award number W81XWH-21-1-0782 and W81XWH-21-1-0783). Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Human CLA+ Memory T Cell and Cytokines in Psoriasis.

Psoriasis is a common inflammatory skin condition resulting from the interplay between epidermal keratinocytes and immunological cellular components. This sustained inflammation is essentially driven by pro-inflammatory cytokines with the IL-23/IL-17 axis playing a critical central role, as proved by the clinical efficacy of their blockade in patients. Among all the CD45R0+ memory T cell subsets, those with special tropism for cutaneous tissues are identified by the expression of the Cutaneous Lymphocyte-associated Antigen (CLA) carbohydrate on their surface, that is induced during T cell maturation particularly in the skin-draining lymph nodes. Because of their ability to recirculate between the skin and blood, circulating CLA+ memory T cells reflect the immune abnormalities found in different human cutaneous conditions, such as psoriasis. Based on this premise, studying the effect of different environmental microbial triggers and psoriatic lesional cytokines on CLA+ memory T cells, in the presence of autologous epidermal cells from patients, revealed important IL-17 cytokines responses that are likely to enhance the pro-inflammatory loop underlying the development of psoriatic lesions. The goal of this mini-review is to present latest data regarding cytokines implicated in plaque and guttate psoriasis immunopathogenesis from the prism of CLA+ memory T cells, that are specifically related to the cutaneous immune system.

Immune changes beyond Th2 pathways during rapid multifood immunotherapy enabled with omalizumab.

Multifood oral immunotherapy (mOIT) with adjunctive anti-IgE (omalizumab, XOLAIR® ) treatment affords safe, effective, and rapid desensitization to multiple foods, although the specific immune mechanisms mediating this desensitization remain to be fully elucidated. Participants in our phase 2 mOIT trial (NCT02643862) received omalizumab from baseline to week 16 and mOIT from week 8 to week 36. We compared the immune profile of PBMCs and plasma taken at baseline, week 8, and week 36 using high-dimensional mass cytometry, component-resolved diagnostics, the indirect basophil activation test, and Luminex. We found (i) decreased frequency of IL-4+ peanut-reactive CD4+ T cells and a marked downregulation of GPR15 expression and CXCR3 frequency among γδ and CD8+ T-cell subsets at week 8 during the initial, omalizumab-alone induction phase; (ii) significant upregulation of the skin-homing receptor CCR4 in peanut-reactive CD4+ T and Th2 effector memory (EM) cells and of cutaneous lymphocyte-associated antigen (CLA) in peanut-reactive CD8+ T and CD8+ EM cells; (iii) downregulation of CD86 expression among antigen-presenting cell subsets; and (iv) reduction in pro-inflammatory cytokines, notably IL-17, at week 36 post-OIT. We also observed significant attenuation of the Th2 phenotype post-OIT, defined by downregulation of IL-4 peanut-reactive T cells and OX40 in Th2EM cells, increased allergen component-specific IgG4/IgE ratio, and decreased allergen-driven activation of indirectly sensitized basophils. This exploratory study provides novel comprehensive insight into the immune underpinnings of desensitization through omalizumab-facilitated mOIT. Moreover, this study provides encouraging results to support the complex immune changes that can be induced by OIT.

The Translational Relevance of Human Circulating Memory Cutaneous Lymphocyte-Associated Antigen Positive T Cells in Inflammatory Skin Disorders.

Circulating memory T cells are heterogeneous in their tissue tropism. The skin-seeking T cell subset expresses the cutaneous lymphocyte-associated antigen (CLA) on their surface. CLA+ memory T cells not only migrate from blood to skin but also recirculate between blood and skin. Studying CLA+ memory T cells in cutaneous diseases has allowed a better understanding of immune-inflammatory mechanisms that take place. The analysis of the phenotypical features of these cells, their antigen specificity, cytokine production profile, and changes in relationship to clinical status and therapies among other characteristics have led to the concept that they constitute peripheral cellular biomarkers in T cell-mediated cutaneous conditions. CLA+ memory T cells are of relevance in the pathogenesis of several cutaneous diseases, such as psoriasis (PSO), atopic dermatitis, vitiligo, and drug-induced allergic reactions, to name a few. The interaction of circulating CLA+ T cells with skin-resident cells has been investigated in different ex vivo coculture models made out of clinical samples. Interestingly, microbes that are present in the skin or related with human skin diseases are preferentially recognized by CLA+ T cells. Thus, the interaction of Streptococcus pyogenes with CLA+ T cells in PSO is providing novel concepts that help to understand disease immunopathogenesis. The goal of this review is to present latest results in the field of CLA+ T cells in T cell-mediated inflammatory skin diseases and their translational relevance for human immunodermatology.

Memory T helper cells identify patients with nickel, cobalt, and chromium metal allergy.

Patch testing is the gold standard for identifying culprit allergens in allergic contact dermatitis; however, it is laborious and positive reactions are difficult to quantitate. Development of complementary in vitro tests is, therefore, of great importance. This study aimed to improve the in vitro lymphocyte proliferation test (LPT) to detect allergic responses to nickel (Ni), cobalt (Co), and chromium (Cr). Twenty-one metal allergic patients with a positive patch test to Ni (n=16), Co (n=8), and Cr (n=3) and 13 controls were included. All were tested by a flow cytometric LPT. Metal-reactive cells were identified as T helper (Th) cells with high expression of the memory marker CD45RO. Skin-homing (cutaneous lymphocyte-associated antigen positive [CLA+]) Ni-reactive memory Th (Thmem hi ) cells identified individuals with a positive patch test for Ni with 100% sensitivity (95% confidence interval [CI] 81%-100%) and 92% specificity (95% CI 67%-100%). Moreover, Co-specific Thmem hi cells expressing CCR6 identified patients with a positive patch test for Co with 63% sensitivity (95% CI 31%-86%) and 100% specificity (95% CI 77%-100%). In Cr allergic individuals, Cr-reactive Thmem hi cells tended to increased CLA and CCR6 expression. Metal-reactive Th cells with high expression of CD45RO and coexpression of CLA and CCR6 improved the LPT, making it an attractive supplement to the patch test.

Metabolic reprogramming augments potency of human pSTAT3-inhibited iTregs to suppress alloreactivity.

Immunosuppressive donor Tregs can prevent graft-versus-host disease (GVHD) or solid-organ allograft rejection. We previously demonstrated that inhibiting STAT3 phosphorylation (pSTAT3) augments FOXP3 expression, stabilizing induced Tregs (iTregs). Here we report that human pSTAT3-inhibited iTregs prevent human skin graft rejection and xenogeneic GVHD yet spare donor antileukemia immunity. pSTAT3-inhibited iTregs express increased levels of skin-homing cutaneous lymphocyte-associated antigen, immunosuppressive GARP and PD-1, and IL-9 that supports tolerizing mast cells. Further, pSTAT3-inhibited iTregs significantly reduced alloreactive conventional T cells, Th1, and Th17 cells implicated in GVHD and tissue rejection and impaired infiltration by pathogenic Th2 cells. Mechanistically, pSTAT3 inhibition of iTregs provoked a shift in metabolism from oxidative phosphorylation (OxPhos) to glycolysis and reduced electron transport chain activity. Strikingly, cotreatment with coenzyme Q10 restored OxPhos in pSTAT3-inhibited iTregs and augmented their suppressive potency. These findings support the rationale for clinically testing the safety and efficacy of metabolically tuned, human pSTAT3-inhibited iTregs to control alloreactive T cells.

Specific IgA and CLA+ T-Cell IL-17 Response to Streptococcus pyogenes in Psoriasis

Streptococcus pyogenes tonsillar infection is well known to trigger and exacerbate psoriasis lesions in both guttate and plaque forms of the disease. Although mucosal and cutaneous tissues are closely involved in psoriasis pathology, the interaction between their specific immune responses has not been deeply explored. This work aims to address and characterize the presence of humoral responses against S.pyogenes in patients with psoriasis and its putative association with cytokine responses detected invitro in our psoriasis exvivo model, based on the coculture of cutaneous lymphocyte-associated antigen+/- T cells with autologous epidermal cells. Patients with psoriasis presented increased IgA response to S.pyogenes when compared with control subjects. In patients with plaque psoriasis, despite being negative for anti-streptolysin O antibody titer, IgA plasma levels against S.pyogenes correlated with cutaneous lymphocyte-associated antigen+ T-cell-dependent IL-17F response invitro. No association is observed for IgG levels in plaque psoriasis. Similar association is observed for IgA anti-S.pyogenes extract and IL-17A in patients with guttate psoriasis. We propose S.pyogenes-specific IgA as a potential new perspective for better understanding the role of S.pyogenes in psoriasis development.

CLA+ T Cell Response to Microbes in Psoriasis.

Streptococcus pyogenes throat infection is a clinically relevant trigger of both guttate and chronic plaque psoriasis, and it provides an ideal context in which to study the pathogenesis of these diseases using an antigen-dependent approach. Circulating cutaneous lymphocyte-associated antigen (CLA) positive (+) memory T cells are a subset of peripheral lymphocytes whose phenotype and function are related to immunological mechanisms in the skin. These cells are considered peripheral biomarkers of T-cell-mediated skin diseases. The coculture of autologous epidermal cells with CLA+ T cells from psoriasis patients activated by S. pyogenes allows the reproduction of the ex vivo initial molecular events that occur during psoriatic lesion formation. With cooperation of autologous epidermal cells, S. pyogenes selectively activates CLA+ T cells both in guttate and plaque psoriasis, inducing key mediators, including an IL-17 response. Here, we explore potential new mechanisms of psoriasis development including the influence of HLA-Cw6 on S. pyogenes CLA+ T cell activation in guttate psoriasis, the relevance of IL-9 on microbe induced IL-17 response in guttate and plaque psoriasis, and novel effector functions of Candida albicans. This review will summarize recent knowledge of psoriatic mechanisms elicited by microbes that have been studied through an innovative translational perspective based on CLA+ T cell-mediated cutaneous immune response.

The psoriasis-protective TYK2 I684S variant impairs IL-12 stimulated pSTAT4 response in skin-homing CD4+ and CD8+ memory T-cells

Tyrosine kinase 2 (TYK2) belongs to the Janus kinase (JAK) family of tyrosine kinases, which transmit signals from activated cytokine receptors. GWAS have consistently implicated TYK2 in psoriasis susceptibility. We performed an in-depth association analysis of TYK2 using GWAS and resequencing data. Strong genetic association of three nonsynonymous variants in the exonic regions of the TYK2 gene (rs34536443, rs12720356, and rs2304256) were found. rs12720356 encoding I684S is predicted to be deleterious based on its location in the pseudokinase domain. We analyzed PBMCs from 29 individuals representing the haplotypes containing each of the significantly associated signals. STAT4 phosphorylation was evaluated by phospho-flow cytometry after CD3/CD28 activation of cells followed by IL-12 stimulation. Individuals carrying the protective I684S variant manifested significantly reduced p-STAT4 levels in CD4 + CD25 + CD45RO+ (mean Stimulation Index (S.I.) 48.08, n = 10) and CD8 + CD25 + CD45RO + cells (S.I. 55.71, n = 10), compared to controls homozygous for the ancestral haplotype (S.I. 68.19, n = 10 (p = 0.002) and 76.76 n = 10 (p = 0.0008) respectively). Reduced p-STAT4 levels were also observed in skin-homing, cutaneous lymphocyte associated antigen (CLA)-positive CD4 and CD8 cells from I684S carriers. No significant changes in p-STAT4 for the psoriasis-associated variant rs34536443 was found. These data establish the functional significance of the TYK2 I684S variant in psoriasis susceptibility.

Anti-epileptic drugs induce cutaneous lymphocyte-associated antigen downregulation leading to potential human herpes virus-7 reactivation in clinically asymptomatic patients

Anti-epileptic drugs induce cutaneous lymphocyte-associated antigen downregulation leading to potential human herpes virus-7 reactivation in clinically asymptomatic patients

Selective Expression of CCR10 and CXCR3 by Circulating Human Herpes Simplex Virus-Specific CD8 T Cells

Herpes simplex virus (HSV) infection is restricted to epithelial cells and neurons and is controlled by CD8 T cells. These cells both traffic to epithelial sites of recurrent lytic infection and to ganglia and persist at the dermal-epidermal junction for up to 12 weeks after lesion resolution. We previously showed that cutaneous lymphocyte-associated antigen (CLA), a functional E-selectin ligand (ESL), is selectively expressed on circulating HSV-2-specific CD8 T cells. CLA/ESL mediates adhesion of T cells to inflamed vascular endothelium. Later stages in T-cell homing involve chemokines (Ch) and lymphocyte chemokine receptors (ChR) for vascular wall arrest and diapedesis. Several candidate ChR have been implicated in skin homing. We measured cell surface ChR on HSV-specific human peripheral blood CD8 T cells and extended our studies to HSV-1. We observed preferential cell surface expression of CCR10 and CXCR3 by HSV-specific CD8 T cells compared to CD8 T cells specific for control viruses, Epstein-Barr virus (EBV) and cytomegalovirus (CMV), and compared to bulk memory CD8 T cells. CXCR3 ligand mRNA levels were selectively increased in skin biopsy specimens from persons with recurrent HSV-2, while the mRNA levels of the CCR10 ligand CCL27 were equivalent in lesion and control skin. Our data are consistent with a model in which CCL27 drives baseline recruitment of HSV-specific CD8 T cells expressing CCR10, while interferon-responsive CXCR3 ligands recruit additional cells in response to virus-driven inflammation.IMPORTANCE HSV-2 causes very localized recurrent infections in the skin and genital mucosa. Virus-specific CD8 T cells home to the site of recurrent infection and participate in viral clearance. The exit of T cells from the blood involves the use of chemokine receptors on the T-cell surface and chemokines that are present in infected tissue. In this study, circulating HSV-2-specific CD8 T cells were identified using specific fluorescent tetramer reagents, and their expression of several candidate skin-homing-associated chemokine receptors was measured using flow cytometry. We found that two chemokine receptors, CXCR3 and CCR10, are upregulated on HSV-specific CD8 T cells in blood. The chemokines corresponding to these receptors are also expressed in infected tissues. Vaccine strategies to prime CD8 T cells to home to HSV lesions should elicit these chemokine receptors if possible to increase the homing of vaccine-primed cells to sites of infection.

The Skin-Brain Connection Hypothesis, Bringing Together CCL27-Mediated T-Cell Activation in the Skin and Neural Cell Damage in the Adult Brain.

Recent discovery of an association of low serum melatonin levels with relapse in multiple sclerosis (MS) opens a new horizon in understanding the pathogenesis of this disease. Skin is the main organ for sensing seasonal changes in duration of sunlight exposure. Level of melatonin production is dependent on light exposure. The molecular mechanisms connecting peripheral (skin) sensing of the light exposure and developing brain inflammation (MS) have not been investigated. We hypothesize that there is a connection between the reaction of skin to seasonal changes in sunlight exposure and the risk of MS and that seasonal changes in light exposure cause peripheral (skin) inflammation, the production of cytokines, and the subsequent inflammation of the brain. In skin of genetically predisposed individuals, cytokines attract memory cutaneous lymphocyte-associated antigen (CLA+) T lymphocytes, which then maintain local inflammation. Once inflammation is resolved, CLA+ lymphocytes return to the circulation, some of which eventually migrate to the brain. Once in the brain these lymphocytes may initiate an inflammatory response. Our observation of increased CC chemokine ligand 27 (CCL27) in MS sera supports the involvement of skin in the pathogenesis of MS. Further, the importance of our data is that CCL27 is a chemokine released by activated keratinocytes, which is upregulated in inflamed skin. We propose that high serum levels of CCL27 in MS are the result of skin inflammation due to exposure to seasonal changes in the sunlight. Future studies will determine whether CCL27 serum level correlates with seasonal changes in sunlight exposure, MS exacerbation, and skin inflammation.

Circulating CLA+ T cells in atopic dermatitis and their possible role as peripheral biomarkers.

Cutaneous lymphocyte-associated antigen (CLA+ ) T cells are specialized for skin homing and represent the main T-cell population in atopic dermatitis (AD) lesions. CLA+ is expressed on the surface of circulating CD45RO+ memory T cells and most skin-infiltrating T cells. Mechanistic studies and thus treatment advancements are limited by the need of large number of skin biopsies. Circulating CLA+ T cells may be a reliable surrogate marker of the inflammatory events occurring in the skin, and thus, the evaluation of CLA+ T cells in the blood may eliminate the need for skin biopsies. Preliminary work in AD has established that disease-associated T-cell abnormalities can be approached by either a study of skin lesions or activated CLA+ T-cell subsets in peripheral blood. Future studies in adults and children, across different skin disorders, correlating blood and skin phenotypes and determining skin-homing T-cell functional properties are needed to establish whether CLA+ memory subsets can be used as biomarkers and a substitute for skin biopsies. This review summarizes the latest advancements reached on circulating CLA+ in AD and the great potential they harbor in understanding AD mechanisms.

MCPIP1 RNase Is Aberrantly Distributed in Psoriatic Epidermis and Rapidly Induced by IL-17A

ZC3H12A, which encodes the RNase monocyte chemotactic protein-induced protein 1 (MCPIP1), is up-regulated in psoriatic skin and reduced to normal levels after clinical treatments with anti-IL-17A/IL-17R neutralizing antibodies. In IL-17A-stimulated keratinocytes, MCPIP1 is rapidly increased at the transcript and protein levels. Also, IL-17A was found to be the main inducer of ZC3H12A expression in keratinocytes treated with supernatants derived from a Streptococcus pyogenes-activated psoriatic exvivo model based on the co-culture of psoriatic cutaneous lymphocyte-associated antigen (CLA(+)) T cells and lesional epidermal cells. Moreover, MCPIP1 was aberrantly distributed in the suprabasal layers of psoriatic epidermis. In psoriatic samples, IL-17A-stimulated epidermal cell suspensions showed an increased MCPIP1 expression, especially in the mid-differentiated cellular compartment. The knockdown of ZC3H12A showed that this RNase participates in the regulation of the mRNAs present in suprabasal differentiated keratinocytes. Furthermore, JAK/STAT3 inhibition prevented the IL-17A-dependent induction of MCPIP1. In the mouse model of imiquimod-induced psoriasis, Zc3h12a expression was abrogated in Il17ra(-/-) mice. These results support the notion that IL-17A-mediated induction of MCPIP1 is involved in the regulation of local altered gene expression in suprabasal epidermal layers in psoriasis.