Skin-homing Cutaneous Lymphocyte Antigen Research Articles

Homing of Regulatory T Cells to Human Skin Is Important for the Prevention of Alloimmune-Mediated Pathology in an In Vivo Cellular Therapy Model

Regulatory T cell (Treg) therapy for immune modulation is a promising therapeutic strategy for the treatment and prevention of autoimmune disease and graft-versus-host disease (GvHD) after bone marrow transplantation. However, Treg are heterogeneous and express a variety of chemokine receptor molecules. The optimal subpopulation of Treg for therapeutic use may vary according to the pathological target. Indeed, clinical trials of Treg for the prevention of GvHD where the skin is a major target of the anti-host response have employed Treg derived from a variety of different sources. We postulated that for the effective treatment of GvHD-related skin pathology, Treg must be able to migrate to skin in order to regulate local alloimmune responses efficiently. To test the hypothesis that different populations of Treg display distinct efficacy in vivo based on their expression of tissue-specific homing molecules, we evaluated the activity of human Treg derived from two disparate sources in a model of human skin transplantation. Treg were derived from adult blood or cord blood and expanded in vitro. While Treg from both sources displayed similar in vitro suppressive efficacy, they exhibited marked differences in the expression of skin homing molecules. Importantly, only adult-derived Treg were able to prevent alloimmune-mediated human skin destruction in vivo, by virtue of their improved migration to skin. The presence of Treg within the skin was sufficient to prevent its alloimmune-mediated destruction. Additionally, Treg expressing the skin homing cutaneous lymphocyte antigen (CLA) were more efficient at preventing skin destruction than their CLA-deficient counterparts. Our findings highlight the importance of the careful selection of an effective subpopulation of Treg for clinical use according to the pathology of interest.

Cutaneous lymphocyte antigen and α4β7 T‐lymphocyte responses are associated with peanut allergy and tolerance in children

It is unclear whether the initial route of allergen exposure in early life could influence the subsequent development of allergy, with cutaneous sensitization leading to peanut allergy (PA), and tolerance induced by oral exposure. The skin- and gastrointestinal (GI)-homing markers, cutaneous lymphocyte antigen (CLA) and α4β7 integrin, are used to determine whether the state of PA correlates with peanut-specific CLA responses, with tolerance associated with predominant α4β7 responses. CLA+ and α4β7+ memory T cells were isolated and cultured with peanut extract to assess their proliferation. Stimulation indices were compared in peanut allergic and non-allergic (NA) groups, and peanut-specific cytokine production was measured. In peanut allergic patients, peanut-specific proliferation predominates in the skin-homing CLA+ subset, whilst peanut-tolerant groups have a mixed CLA/α4β7 response (P = 0.008). Comparison with a control food antigen (ovalbumin) showed that these differences are allergen specific. Cytokine responses showed trends towards Th1 skewing in the GI-homing α4β7+ cells of peanut-tolerant groups and Th2 skewing in the skin-homing CLA+ cells of peanut allergic patients. The predominance of the CLA+ response to peanut in peanut allergic patients is consistent with the hypothesis that allergic sensitization occurs through the skin. The predominant α4β7+ response in peanut-tolerant groups suggests that allergen exposure through the GI tract induces tolerance.

IL-31 is associated with cutaneous lymphocyte antigen–positive skin homing T cells in patients with atopic dermatitis

IL-31 is a newly discovered T-cell cytokine that, when overexpressed in mice, results in pruritus and skin dermatitis resembling human atopic dermatitis (AD). We sought to investigate the expression of IL-31 and IL-31 receptor A (IL-31RA) in skin biopsy specimens and peripheral blood cells from patients with AD and healthy individuals. Expression of IL-31 and IL-31RA was evaluated in skin biopsy specimens from patients with AD and healthy individuals by means of immunohistochemistry and RT-PCR. IL-31 protein production by skin-homing cutaneous lymphocyte antigen (CLA)-positive T cells was also assessed. IL-31RA protein was expressed by keratinocytes and infiltrating macrophages in skin biopsy specimens from patients with AD. Comparisons between skin from patients with AD and healthy skin showed IL-31RA expression at higher levels on epidermal keratinocytes in AD samples. Infiltrating cells, more numerous in skin from patients with AD compared with that of healthy individuals, expressed IL31 mRNA. Histomorphometric analysis of these cells indicated they were of the lymphocytic lineage, with the majority of cells staining positive for CLA and CD3. IL31 mRNA and protein expression is largely restricted to CD45RO(+) (memory) CLA(+) T cells in peripheral blood of patients with AD and healthy volunteers. Moreover, circulating CLA(+) T cells from patients with AD, but not from patients with psoriasis, are capable of producing higher levels of IL-31 compared with CLA(+) T cells from healthy individuals. However, the average levels of IL-31 were not significantly different between patients with AD and healthy individuals. We provide evidence that IL-31 expression is associated with CLA(+) T cells and might contribute to the development of AD-induced skin inflammation and pruritus.

Absence of CD26 expression on skin-homing CLA+ CD4+ T lymphocytes in peripheral blood is a highly sensitive marker for early diagnosis and therapeutic monitoring of patients with Sezary syndrome

Patients with Sézary syndrome (SS) show clonal expansion in the peripheral blood of skin-homing CD4+ T-helper cells expressing cutaneous lymphocyte antigen (CLA). However, an increase of CLA+ CD4+ T cells can also be observed in various inflammatory dermatoses. To facilitate early diagnosis and therapeutic monitoring of SS using flow cytometry, we evaluated the expression of CD7 and CD26 on the CLA+ CD4+ lymphocyte subset. Peripheral lymphocytes from 7 patients with SS, 16 patients with mycosis fungoides (MF) and 11 healthy controls were analysed by flow cytometry for the expression of CD4, CD7, CD26, CLA and CCR4. In addition, a longitudinal study was performed over 16 months in two patients with SS. Absence of CD7 and CD26 on CLA+ CD4+ T cells was highly specific for SS. Importantly, the absence of CD26 on CLA+ CD4+ T cells was very sensitive for SS, at 100% in our patient cohort. The number of CD26- CLA+ CD4+ T cells closely correlated with therapeutic interventions in the longitudinal analysis of two patients over more than 1 year. We conclude that the absence of CD26 expression on skin-homing CLA+ CD4+ T-helper cells is a very sensitive and highly specific parameter for early diagnosis and therapeutic monitoring of patients with SS.

Cutaneous lymphocyte antigen expression on activated lymphocytes and its association with IL-12R (β1 and β2), IL-2Rα, and CXCR3

The majority of T lymphocytes that infiltrate psoriatic lesions express cutaneous lymphocyte antigen (CLA), a skin homing receptor involved in the influx of memory T cells to cutaneous sites. We investigated CLA expression on normal human peripheral blood mononuclear cells (PBMCs) and evaluated its association with IL-12 receptors, chemokine receptor, CXCR3, and IL-2Rα. PBMCs were stimulated in vitro with or without polyclonal activators (mitogen, or superantigens, or anti-CD3 + anti-CD28) in the presence or absence of exogenous rhIL-12. The percentage of CLA+ T lymphocytes increased significantly after superantigen stimulation compared to anti-CD3 + anti-CD28 or mitogen activation. The majority of activation induced CLA+ T lymphocytes co-expressed IL-12Rβ1, IL-12Rβ2, CXCR3, and CD25 in the presence of rhIL-12. Our results indicate that CLA expression on activated T lymphocytes is IL-12 and activation dependent and correlates with the expression of IL-12 receptors, IL-2Rα, and CXCR3. Monitoring the levels of Th1 differentiation markers such as CXCR3 and IL-12Rβ2 along with activation marker, CD25 on skin homing CLA+ T lymphocytes may provide insight into the mechanism of action of immunotherapies directed against Th1 type skin inflammatory diseases.