Natural cell-mediated cytotoxicity in vitiligo

How Does Vitamin D Affect Immune Cells Crosstalk in Autoimmune Diseases?

Vitamin D is a secosteroid hormone that is highly involved in bone health. Mounting evidence revealed that, in addition to the regulation of mineral metabolism, vitamin D is implicated in cell proliferation and differentiation, vascular and muscular functions, and metabolic health. Since the discovery of vitamin D receptors in T cells, local production of active vitamin D was demonstrated in most immune cells, addressing the interest in the clinical implications of vitamin D status in immune surveillance against infections and autoimmune/inflammatory diseases. T cells, together with B cells, are seen as the main immune cells involved in autoimmune diseases; however, growing interest is currently focused on immune cells of the innate compartment, such as monocytes, macrophages, dendritic cells, and natural killer cells in the initiation phases of autoimmunity. Here we reviewed recent advances in the onset and regulation of Graves' and Hashimoto's thyroiditis, vitiligo, and multiple sclerosis in relation to the role of innate immune cells and their crosstalk with vitamin D and acquired immune cells.

Transcriptome analysis reveals markers of aberrantly activated innate immunity in vitiligo lesional and non-lesional skin

BACKGROUND

Vitiligo is characterized by the death of melanocytes in the skin. This is associated with the presence of T cell infiltrates in the lesional borders. However, at present, there is no detailed and systematic characterization on whether additional cellular or molecular changes are present inside vitiligo lesions. Further, it is unknown if the normal appearing non-lesional skin of vitiligo patients is in fact normal. The purpose of this study is to systematically characterize the molecular and cellular characteristics of the lesional and non-lesional skin of vitiligo patients.

METHODS AND MATERIALS

Paired lesional and non-lesional skin biopsies from twenty-three vitiligo patients and normal skin biopsies from sixteen healthy volunteers were obtained with informed consent. The following aspects were analyzed: (1) transcriptome changes present in vitiligo skin using DNA microarrays and qRT-PCR; (2) abnormal cellular infiltrates in vitiligo skin explant cultures using flow cytometry; and (3) distribution of the abnormal cellular infiltrates in vitiligo skin using immunofluorescence microscopy.

RESULTS

Compared with normal skin, vitiligo lesional skin contained 17 genes (mostly melanocyte-specific genes) whose expression was decreased or absent. In contrast, the relative expression of 13 genes was up-regulated. The up-regulated genes point to aberrant activity of the innate immune system, especially natural killer cells in vitiligo. Strikingly, the markers of heightened innate immune responses were also found to be up-regulated in the non-lesional skin of vitiligo patients.

CONCLUSIONS AND CLINICAL IMPLICATIONS

As the first systematic transcriptome characterization of the skin in vitiligo patients, this study revealed previously unknown molecular markers that strongly suggest aberrant innate immune activation in the microenvironment of vitiligo skin. Since these changes involve both lesional and non-lesional skin, our results suggest that therapies targeting the entire skin surface may improve treatment outcomes. Finally, this study revealed novel mediators that may facilitate future development of vitiligo therapies.

Estudo comparativo entre vitiligo, nevo halo e lúpus eritematoso vitiligóide por meio de métodos imunológicos, histológicos e imuno-histoquímicos

FUNDAMENTOS: O estudo compara o vitiligo, o nevo halo (NH) e lúpus eritematoso vitiligóide (LEV) do ponto de vista imunológico, histológico e histoquímico. OBJETIVOS: Avaliar diferenças imuno-histoquímicas entre essas doenças e investigar se a despigmentação do LEV deve-se à destruição pós-inflamatória ou à agressão imunológica aos melanócitos. MÉTODOS: Foram avaliados 20 pacientes com vitiligo, 17 com vitiligo e NH, cinco com NH isolado e 15 com LEV. Detecção de anticorpos: IF direta e indireta com células névicas e de melanoma. Citotoxicidade: atividade NK contra células de melanoma. Estudo anátomo-histoquímico: exame histológico com hematoxilina e eosina, Fontana-Masson, Dopa e Dopa mais prata (D+P) e exame histoquímico com proteína S-100. RESULTADOS: Doentes com vitiligo, NH e LEV apresentaram anticorpos antimelanócitos. Tanto no vitiligo e NH, como no LEV, demonstrou-se a presença de fatores de risco favorecedores da citotoxicidade celular. A coloração com D+P foi superior às colorações tradicionais e à proteína S-100 na detecção de melanócitos e melanina nas lesões de vitiligo, NH e LEV. CONCLUSÕES: Demonstrou-se a existência de anticorpos antimelanócitos no vitiligo e NH. É possível que a despigmentação no LEV se deva a fenômenos imunológicos semelhantes aos do vitiligo e NH. A detecção de melanócitos nas lesões de vitiligo sugere mais inibição funcional do que destruição dessas células.

Topical tacrolimus for repigmentation of vitiligo

We describe 6 patients with generalized vitiligo who responded to treatment with tacrolimus ointment. Moderate to excellent repigmentation was achieved in 5 patients. Although the number of cases in this noncontrolled, nonblinded series is small, tacrolimus ointment may be an efficacious and safe treatment option for vitiligo.

Inflammatory vitiligo in Vogt-Koyanagi-Harada disease

Vogt-Koyanagi-Harada disease is a rare disease characterized by uveitis, meningitis, dysacusis, alopecia, poliosis, and vitiligo. We describe a 48-year-old patient with Vogt-Koyanagi-Harada disease associated with thin inflammatory raised erythema and plaque-type inflammatory erythema superimposed on vitiligo. Interestingly, inflammatory raised erythema was separated from the perfect vitiligo, and the incomplete vitiligo lay between them initially. Thereafter, incomplete vitiligo became completely depigmented with diminution of inflammatory raised erythema. This is the second case of vitiligo with inflammatory raised borders associated with Vogt-Koyanagi-Harada disease. Our results of immunohistochemical and electron microscopic studies suggested the involvement of T-cell-mediated cytotoxicity and apoptosis in the development of skin lesions.

Cytomegalovirus DNA identified in skin biopsy specimens of patients with vitiligo

BACKGROUND

Viral infections have been implicated in the pathogenesis of a variety of autoimmune diseases.

OBJECTIVE

This investigation was undertaken to determine the presence or absence of viral genomes in the depigmented and uninvolved skin of patients with vitiligo.

METHODS

A polymerase chain reaction assay was used to detect viral genomes in paraffin-embedded skin biopsy specimens. Twenty-nine patients with vitiligo and 22 control subjects were included. Biopsy specimens were screened in a blinded fashion for a panel of DNA and RNA viruses including herpes simplex, varicella-zoster, cytomegalovirus (CMV), Epstein-Barr, HIV, and human T-cell lymphotropic virus.

RESULTS

CMV DNA was identified in 38% of the patients studied. Twenty-one percent had indeterminate results. Results in all control subjects were negative. Polymerase chain reaction screening for identification of other viral genomes was negative. Although not statistically significant, data trends suggested a correlation between the presence of CMV DNA in biopsy specimens and active vitiligo of relatively brief duration. In addition, CMV-positive patients had a statistically significant increased frequency of other concurrent autoimmune diseases.

CONCLUSION

CMV DNA in the depigmented and uninvolved skin of some patients with vitiligo and its absence in control subjects suggest that vitiligo may indeed be triggered by a viral infection in select patients.

Natural killer cell and lymphokine-activated killer cell activity against melanocytes in vitiligo

BACKGROUND

Vitiligo is a common disease of unknown cause. Previous studies have shown abnormalities in natural killer (NK) cell cytotoxicity in patients when NK-sensitive erythroleukemic cell lines were used as target cells.

OBJECTIVE

The purpose of this study was to use melanocytes directly as target cells to determine NK and lymphokine-activated killer (LAK) cell cytotoxicity in patients with vitiligo and to determine whether NK or LAK cells can be implicated in any destructive mechanism for melanocyte cytotoxicity in vitro in this disease.

METHODS

Twenty-one patients with vitiligo were compared with a control group by studying NK cell activity (NKCA) and LAK cell activity (LAKCA) on several target cells. These included K562 cells, neonatal melanocytes, and malignant melanoma cells for NKCA and neonatal melanocytes and malignant melanoma cells for LAKCA. Cytotoxicity was measured with the standard chromium 51-release assay.

RESULTS

No significant differences were found between vitiligo patients and control subjects in NKCA against K562 cells or in NKCA and LAKCA against melanocytes.

CONCLUSION

NK cells and LAK cells are probably not responsible for melanocyte destruction in vitiligo.

Coexistence and relationship of antikeratinocyte and antimelanocyte antibodies in patients with non-segmental-type vitiligo

To test for autoantibodies in patients with vitiligo, skin biopsies from 16 patients with active vitiligo and 12 patients with stable vitiligo were examined by direct immunofluorescence. In periodate-lysine-paraformaldehyde-fixed biopsy specimens, the presence of IgG deposits in keratinocytes and the number of keratinocytes with focal IgG in active vitiligo were significantly greater than in stable vitiligo. To test whether the antibodies to normal human keratinocytes or melanocytes are present in vitiligo, we used an indirect immunofluorescent test and enzyme-linked immunosorbent assay to test the serum of 43 patients. With unfixed viable melanocytes, we found a granular pattern of IgG staining on the plasma membrane of melanocytes incubated with patients' sera but not in cells incubated with the control sera. With methanol-fixed melanocytes, however, we found a homogeneous pattern of IgG staining in the cytoplasm of melanocytes. With unfixed viable keratinocytes as targets, there was no deposit of IgG on the cells. A homogeneous pattern of IgG binding in the cytoplasm of methanol-fixed keratinocytes suggested the presence of antikeratinocyte autoantibodies to cytoplasmic keratinocyte components. The fluorescence staining for IgG binding was more prominent in active or extensive vitiligo. Vitiligo sera were cytotoxic for melanocytes but not for keratinocytes in vitro. Antimelanocytic antibodies may play a role in melanocytotoxicity, whereas antikeratinocyte antibodies may occur secondary to cellular damage.

Vitiligo: where do we stand?

Vitiligo is a puzzling disorder characterized by a disappearance of epidermal and/or follicular melanocytes by unknown mechanisms. This very common disorder involving 1-4% of the world population is thus of great importance for the practicing dermatologist. The cellular and molecular mechanisms leading to the destruction of melanocytes in this disorder have not yet been elucidated, making it of major interest for the cell biologist involved in melanocyte research. Recent advances in this field, due largely to the availability of techniques for culturing normal human melanocytes, opened new perspectives in the understanding of vitiligo. Although vitiligo has long been considered a disorder confined to the skin, there is now good evidence that it also involves the extracutaneous compartment of the "melanocyte organ." It is also clear that vitiligo is not only a melanocyte disorder, but that it also involves cells, such as keratinocytes and Langerhans cells, found in the epidermis and follicular epithelium. The three prevailing theories of the pathogenesis of vitiligo are the immune hypothesis, the neural hypothesis, and the self-destruct hypothesis. New hypotheses suggest that vitiligo may be due to (1) a deficiency in an unidentified melanocyte growth factor, (2) an intrinsic defect of the structure and function of the rough endoplasmic reticulum in vitiligo melanocytes, (3) abnormalities in a putative melatonin receptor on melanocytes and (4) a breakdown in free radical defense in the epidermis. None of these hypotheses has been demonstrated, and according to the available data, it is likely that the loss of epidermal and follicular melanocytes in vitiligo may be the result of several different pathogenetic mechanisms.

Nonsegmental vitiligo: decrease of the CD45RA+ T-cell subset and evidence for peripheral T-cell activation

Peripheral T-lymphocytes from 16 randomly selected patients with nonsegmental vitiligo were labeled with monoclonal antibodies recognizing T-cell receptor (TCR) alpha/beta, TCR gamma/delta, CD3, CD4, CD8, CD45RA, CD45RO, CD11b, CD11c, CD16, CD56, CD25, CD54, and HLA-DR antigens. In comparison with matched controls, a significant decrease of the CD45RA+ subset (P less than 0.03) together with significant increase of the circulating HLA-DR+ cells (P less than 0.02) was found. No other alterations were detected. These findings may point to some autoimmune phenomena involved in the pathogenesis of the disease. The increased HLA-DR expression indicates the presence of activated peripheral T-cells. Thus, our data provide new and further evidence for T-cell dysregulation in nonsegmental vitiligo.

Depletion and repopulation of Langerhans cells in nonsegmental type vitiligo

The role of Langerhans cells in the pathogenesis of nonsegmental type vitiligo is still unknown. In this study, biopsies were taken from 26 patients at various stages of nonsegmental type vitiligo and morphometrically observed to investigate the kinetics of Langerhans cells in patients at various stages of the disease. A marked depletion of OKT6-positive and ATPase-positive epidermal dendritic cells was noted in patients with active nonsegmental type vitiligo. A repopulation of both OKT6-positive and ATPase-positive epidermal dendritic cells was noted in patients with stable nonsegmental type vitiligo. Profound depletion of epidermal OKT6-positive and ATPase-positive dendritic cells was noted in patients with repigmenting nonsegmental type vitiligo receiving treatments involving topical use of 0.05% Fluocinonide cream or PUVA photochemotherapy. Transmission electron microscopy confirmed the absence of epidermal dendritic cells (Langerhans cells and intermediate cells) in patients with active and repigmenting nonsegmental type vitiligo. In active nonsegmental type vitiligo, two possible explanations are proposed for the depletion of OKT6-positive and ATPase-positive epidermal dendritic cells (presumptive Langerhans cells): 1) the cells are destroyed by cytotoxic factors released during the course of destruction of melanocytes in active vitiligo, and/or 2) they leave the epidermis and migrate to regional lymph nodes to present certain antigens which are released from certain destroyed epidermal cells (keratinocytes or melanocytes) during the course of active vitiligo. The repopulated epidermal Langerhans cells may result from phenotypically transformed dermal dendritic cells in the depigmented lesions of patients with stable vitiligo. Since various therapies which result in repigmentation deplete the density of epidermal Langerhans cells markedly, it is suggested that depletion of epidermal Langerhans cells in stable vitiligo may aid in repigmentation. It is also proposed that the repopulated epidermal Langerhans cells may play a role in inhibiting the proliferation of epidermal melanocytes in depigmented lesions of stable vitiligo, thus various methods of treatment which deplete the Langerhans cells may eventually aid in the repigmentation of nonsegmental type vitiligo.

Repigmentation of vitiliginous skin by cultured cells

Epidermal cells from pigmented areas of a patient with vitiligo were cultured in MCDB-153 medium, which supports the clonal growth of undifferentiated keratinocytes and melanocytes. The cells were grown on collagen-coated substrata. After the cells reached semiconfluence, the composite of substratum and cells was emplaced onto dermabraded vitiliginous areas as a graft. Re-epithelialization of the grafted areas was complete after 2 weeks. Repigmentation was evident after 1 month and continued over the observation period of several months. There was complete and normal differentiation of the graft, including a normal distribution of melanocytes in the basal layer. Ultrastructural studies showed a normal distribution of melanosomes in the melanocytes and showed keratinocytes that were indistinguishable from the uninvolved skin.

Abrogated NK-cell lysis of human papillomavirus (HPV)-16-bearing keratinocytes in patients with pre-cancerous and cancerous HPV-induced anogenital lesions

Natural-cell-mediated cytotoxicity against K-562 erythroleukemic cells and human papillomavirus (HPV)-16 harboring Sk-v keratinocytes was tested in 38 age- and sex-matched healthy volunteers and in patients with HPV-induced benign and malignant anogenital lesions: 9 persons with HPV-16-induced bowenoid papulosis (BP), 8 with anogenital carcinomas (5 with HPV-16- or 33-associated squamous-cell carcinomas of Bowen's type and 3 with HPV-6-associated Buschke-Loewenstein verrucous carcinomas) and 12 with HPV-6-induced condylomata acuminata. Both K-562 and Sk-v cells were killed by a non-adherent CD16+ subset of PBMC as revealed by cell fractionation on the basis of their adherence to plastic and by treatment with Leu-IIb monoclonal antibody (MAb) and complement. "Cold" target competitive assays demonstrated that both cell types inhibited lysis of labelled Sk-v cells. In patients with BP and anogenital carcinomas induced by HPV-16 or 33, there was a significant (at least at p less than 0.01) decrease of Sk-v cell lysis as compared with the healthy control group. Anti-K-562 activity was not affected. In patients with anogenital carcinomas the degree of Sk-v lysis was decreased in proportion to the duration of lesions (correlation coefficient-r = -0.79). Neither anti-K-562 nor anti-Sk-v cytotoxicities were significantly affected in patients with condylomata and with HPV-6 associated verrucous carcinomas. Short-term (3 hr) pre-incubation of normal PBMC with sera from patients with BP and HPV-16-associated anogenital carcinomas resulted in significant inhibition of their ability to lyse Sk-v cells. Lysis of K-562 cells remained unaffected. In patients with carcinomas, the suppressive effect of sera was associated with a lowering of the ability of their PBMC to lyse Sk-v cells (r = -0.79). In patients with longer tumor persistence, the suppressive effect of serum was proportionally higher (r = 0.86).