Cytolytic antibodies to melanocytes in vitiligo

A Hospital-Based Case-Control Study on Raised Homocysteine Level in Vitiligo Patients and Its Association With Disease Severity

Introduction Vitiligo is an acquired pigmentary disorder clinically manifested by circumscribed depigmented macules and often associated with leucotrichia. Not much is known about the biochemical abnormality occurring in vitiligo. Our study aims to determine whether serum homocysteine is raised in vitiligo patients and whether it can be used as a prognostic marker for vitiligo. Material and methods This study is a hospital-based, case-control, analytical study conducted on 70 patients of vitiligo patients. A total of 30 staff of the hospital served as control. Venous blood was withdrawn from the antecubital vein from all study participants using all aseptic precautions. Investigation of blood homocysteine levels was done in all the study participants. Scoring of vitiligo was done based on Vitiligo European Task Force (VETF) criteria which take into account body surface area, stage, and spread. Results Mean serum homocysteine level among vitiligo patients was 14.40± 5.80 micromoles/lit as compared to 10.33± 5.05 micromole/lit in control groups, and this difference was statistically significant (t-value = 3.19and p-value = 0.002). The correlation coefficient was statistically significant (correlation coefficient = 0.25 and p-value = 0.03) in between homocysteine level and stage of the disease. On multiple comparisons difference in serum homocysteine level of progressing category is significantly raised as compared to control, stable, and regressing categories. Conclusion The mean serum homocysteine level among all vitiligo patients was higher as compared to control groups. Moreover, the serum homocysteine level of active cases is significantly higher as compared to control, stable, and regressing categories. Also, serum homocysteine levels showed a positive correlation with the degree of depigmentation, i.e., stage of the disease.

Current Debates on Etiopathogenesis and Treatment Strategies for Vitiligo

Vitiligo is an acquired, chronic, and progressive depigmentation or hypopigmentation characterized by the destruction of melanocytes and the occurrence of white patches or macules in the skin, mucosal surface of eyes, and ears. Melanocytes are the melanin pigment-producing cells of the skin which are destroyed in pathological conditions called vitiligo. Approximately 0.5 - 2.0% of the population is suffering from vitiligo, and a higher prevalence rate of up to 8.8% has been reported in India. It is caused by various pathogenic factors like genetic predisposition, hyperimmune activation, increased oxidative stress, and alteration in neuropeptides level. Genetic research has revealed a multi- genetic inheritance that exhibits an overlap with other autoimmune disorders. However, melanocytes specific genes are also affected (such as DDR1, XBP1, NLRP1, PTPN22, COMT, FOXP3, ACE, APE, GSTP1, TLR, SOD, and CTLA-4). A number of therapeutic options are employed for the treatment of vitiligo. The topical corticosteroids and immunomodulators are currently in practice for the management of vitiligo. Phototherapies alone and in combinations with other approaches are used in those patients who do not respond to the topical treatment. The main focus of this review is on the etiopathological factors, pharmacological management (phototherapy, topical, systemic, and surgical therapy), and herbal drugs used to treat vitiligo.

Vitiligo: Mechanisms of Pathogenesis and Treatment

Vitiligo is an autoimmune disease of the skin that targets pigment-producing melanocytes and results in patches of depigmentation that are visible as white spots. Recent research studies have yielded a strong mechanistic understanding of this disease. Autoreactive cytotoxic CD8+ T cells engage melanocytes and promote disease progression through the local production of IFN-γ, and IFN-γ-induced chemokines are then secreted from surrounding keratinocytes to further recruit T cells to the skin through a positive-feedback loop. Both topical and systemic treatments that block IFN-γ signaling can effectively reverse vitiligo in humans; however, disease relapse is common after stopping treatments. Autoreactive resident memory T cells are responsible for relapse, and new treatment strategies focus on eliminating these cells to promote long-lasting benefit. Here, we discuss basic, translational, and clinical research studies that provide insight into the pathogenesis of vitiligo, and how this insight has been utilized to create new targeted treatment strategies.

Antimelanocyte Antibodies: A Possible Role in Patients with Vitiligo

Background:

Vitiligo is an acquired depigmenting skin disorder with multifactorial pathogenesis including genetic, autoimmune, and neuronal factors. Both humoral- and cell-mediated immunities are supposed to have a role in the pathogenesis of vitiligo. Patients with vitiligo have an increased concentration of circulating autoantibodies that are specific to melanocyte cytoplasm and surface antigens that related to the extent of the disease.

Aims and Objectives:

The aim of the present study was to evaluate the role of antimelanocyte antibodies (AMAs), complement 3 and 4 (C3 and C4), and antinuclear antibodies (ANAs) in the pathogenesis of vitiligo.

Materials and Methods:

This study included 49 patients with nonsegmental vitiligo and 36 healthy individuals as a control group. All participants were subjected to detailed history, general examination, and detailed dermatological examination of the skin, hair, nails, and oral mucosa. The severity of vitiligo was assessed according to the Vitiligo Area Scoring Index (VASI). AMA, C3 and C4, and ANA serum levels were measured for patients and controls.

Results:

ANA, AMA, and C4 levels were significantly higher in the sera of patients than in controls. ANA, AMA, and C4 serum levels showed significant positive correlations with VASI score.

Conclusion:

Our results support the role of AMA in the pathogenesis of nonsegmental vitiligo, correlating with the disease extent and severity. However, a longitudinal study in a large cohort of patients to evaluate the clinical and predictive value of AMA is warranted.

A cross-sectional study of spontaneous repigmentation in vitiligo

Background

Spontaneous regression is well documented in several chronic skin diseases such as psoriasis, alopecia areata, and atopic dermatitis. However, information on vitiligo is scarce.

Aims

We studied the frequency, extent, and factors affecting spontaneous repigmentation in vitiligo.

Methods

A cross-sectional descriptive study was undertaken in 167 patients with vitiligo with an emphasis on history of spontaneous repigmentation. Where available, photographs documenting spontaneous repigmentation were also obtained. Repigmentation was defined as spontaneous if it occurred when the patient was off treatment for at least 3 consecutive months.

Results

Spontaneous repigmentation occurred in 36 (21.5%) patients with complete repigmentation in 6 (3.6%) patients. The extent varied from 0.5% to 100% (mean, 35.4 ± 37.9%) of vitiliginous skin. It occurred after 3 months to 47 years (mean, 8.7 ± 9.5 years) of onset of vitiligo and persisted for 2 months to 27 years (mean, 4.4 ± 6.2 years). Diffuse repigmentation was the most common pattern observed in 20 (55.6%) patients and there was a good color match in 26 (72.2%) patients. Likelihood of spontaneous repigmentation was 3.5 times greater in patients with more than 3 years of stable disease (P = 0.001).

Limitations

The chief limitation was the dependence on patient recall for the data, except when documented by images.

Conclusion

Spontaneous repigmentation occurs in one-fifth of patients with vitiligo. In some patients, the repigmentation is clinically significant and long-lasting. Considering its frequency and extent, spontaneous repigmentation should be taken into account both when evaluating novel interventions and counselling patients about the course of the disease.

Imbalance of peripheral follicular helper T lymphocyte subsets in active vitiligo

Vitiligo is an autoimmune disease characterized by the presence of several autoantibodies, some of which are directed against melanocyte components and have been shown to be associated with the progression of the disease. However, the mechanism involved in the production of autoantibodies remains unclear. Follicular helper CD4⁺ T cells (TFH) are specialized in B-cell activation and antibody production, especially the TFH cell subsets type 2 and type 17. To date, TFH cell subsets have not been studied in human vitiligo. This study in 44 vitiligo patients and 19 healthy controls showed an increase in circulating TFH cells associated with disease clinical progression. A more precise analysis of TFH cell phenotype demonstrated that vitiligo is characterized by populations of peripheral TFH cells responsible for helping B-cell function, such as TFH type 2 and type 17 which produce Th2- and TH17-related cytokines, respectively. These findings suggest a new mechanism involving TFH cell subsets in the pathogenesis of human vitiligo and leading to the production of autoantibodies and disease.

The convergence theory for vitiligo: A reappraisal

Vitiligo is characterized by progressive loss of skin pigmentation. The search for aetiologic factors has led to the biochemical, the neurologic and the autoimmune theory. The convergence theory was then proposed several years ago to incorporate existing theories of vitiligo development into a single overview of vitiligo aetiology. The viewpoint that vitiligo is not caused only by predisposing mutations, or only by melanocytes responding to chemical/radiation exposure, or only by hyperreactive T cells, but rather results from a combination of aetiologic factors that impact melanocyte viability, has certainly stood the test of time. New findings have since informed the description of progressive depigmentation. Understanding the relative importance of such aetiologic factors combined with a careful selection of the most targetable pathways will continue to drive the next phase in vitiligo research: the development of effective therapeutics. In that arena, it is likewise important to acknowledge that pathways affected in some patients may not be altered in others. Taken together, the convergence theory continues to provide a comprehensive viewpoint of vitiligo aetiology. The theory serves to intertwine aetiologic pathways and will help to define pathways amenable to disease intervention in individual patients.

Biomarkers of disease activity in vitiligo: A systematic review

The pathophysiology of vitiligo is complex although recent research has discovered several markers which are linked to vitiligo and associated with disease activity. Besides providing insights into the driving mechanisms of vitiligo, these findings could reveal potential biomarkers. Activity markers can be used to monitor disease activity in clinical trials and may also be useful in daily practice. The aim of this systematic review was to document which factors have been associated with vitiligo activity in skin and blood. A second goal was to determine how well these factors are validated in terms of sensitivity and specificity as biomarkers to determine vitiligo activity. Both in skin (n=43) as in blood (n=66) an adequate number of studies fulfilled the predefined inclusion criteria. These studies used diverse methods and investigated a broad range of plausible biomarkers. Unfortunately, sensitivity and specificity analyses were scarce. In skin, simple histopathology with or without supplemental CD4 and CD8 stainings can still be considered as the gold standard, although more recently chemokine (C-X-C motif) ligand (CXCL) 9 and NLRP1 have demonstrated a good and possibly even better association with progressive disease. Regarding circulating biomarkers, cytokines (IL-1β, IL-17, IFN-γ, TGF-β), autoantibodies, oxidative stress markers, immune cells (Tregs), soluble CDs (sCD25, sCD27) and chemokines (CXCL9, CXCL10) are still competing. However, the two latter may be preferable as both chemokines and soluble CDs are easy to measure and the available studies display promising results. A large multicenter study could make more definitive statements regarding their sensitivity and specificity.

Clinicopathologic Analysis of Stable and Unstable Vitiligo: A Study of 66 Cases

Vitiligo is an acquired skin disorder characterized by milky-white macules and absence of functioning melanocytes. The cornerstone of its management is the correct categorization of a case into its 2 broad types-stable and unstable vitiligo. This distinction is at present based mainly on clinical criteria because the histopathological features are not fully established. This study was thus undertaken to examine histopathological features of vitiligo and to come up with a reliable and systematic approach toward this diagnostic challenge. All patients presenting with clinical features of vitiligo at our institution were included in the study. A 3-mm punch biopsy was taken from 3 sites-lesional, perilesional, and normal skin. Histopathological examination was primarily focused on evaluating 5 histopathological variables-spongiosis, epidermal lymphocytes, basal cell vacuolation, dermal lymphocytes, and melanophages. A total number of 66 patients were included in the study. There were 30 patients in stable and 36 in unstable vitiligo groups. It was observed that all 5 histopathological pattens were associated with unstable vitiligo. All the cases were then scored using a scoring system devised by the authors and the scores obtained were correlated with clinical categorization. It was observed that while there is a definite overlap in histological findings in the 2 groups, adoption of a systematic reporting system brings more consistency and objectivity in the diagnosis. The authors have recommended diagnoses that should be reported for the various scores. This in turn will help us to more reliably and confidently manage these patients.

Detection of auto antibodies and transplantation of cultured autologous melanocytes for the treatment of vitiligo

The aim of the present study was to establish an immunofluorescence method of antibody detection to identify melanocytes in the serum of vitiligo patients. Furthermore, we aimed to establish a method for the culture and proliferation of autologous pure melanocytes and to observe the effect of their transplantation for the treatment of vitiligo. Suspension of epidermal cells with melanocytes was performed using trypsin digestion of normal epiderm from eyelid operation and melanocytes were selectively cultured and proliferated in serum-free M2 medium. FITC-labeled rabbit anti-human antibody was used to detect the relative fluorescence intensity of the melanocytes. After identification with immunological and biological examinations, the melanocytes were transplanted to depigmented areas of vitiligo. Repigmentation was observed continuously. The results indicated that melanocytes could be selectively proliferated in the medium. Subsequently, pure melanocytes without contamination of fibroblast and keratinocyte were harvested. A total of 34 patients suffering vitiligo for between 3 months and 20 years with depigmented area (between 4 cm² and 70% of body surface) were divided into 19 cases of developing stage and 15 cases of stable stage, according to the change of depigmentation. A total of 15 developing cases were positive for the antibody against melanocytes, with the positive rate of 79%. The titers of serum was >1:50 in 10 patients at the developing stage, and 5 developing patients were 1:10. Among the 15 stable cases, four were positive, with a positive rate of 27%. Fluorescence of antibody was localized in the cytoplasm of the melanocytes. Autologous melanocytes of vitiligo patients could be selectively proliferated in the medium. Next, pure melanocytes without contamination with fibroblasts and keratinocytes were harvested. A total of 16 vitiligo patients with 28 depigmented areas (2–200 cm²) were treated with transplantation of melanocytes. Repigmentation of the transplanted areas appeared as red coloration after one month. All the vitiligous areas received transplantation were repigmented significantly with hypo- or hyper-pigmentation after 3–5 months. After 6–8 months, 87.5% of lesions showed repigmentation of >50% of the lesion area. No scarring or other side-effects occurred. After follow-up of 5 years, no relapse was observed in transplantation area. Thus, an immunofluorescence method for the test of antibody to melanocytes in the serum of vitiligo patients was established. Transplantation of cultured autologous melanocytes was an effective and safe measure for treatment of vitiligo, particularly for patients with a large depigmented area.

Systemic Steroids Suppress Antimelanocyte Antibodies in Vitiligo

Background:

Vitiligo is associated with autoantibodies to melanocytes. The role of these antibodies in the pathogenesis of the disease is still unknown.

Objective:

The purpose of this study was to examine the role of vitiligo antibodies in the pathogenesis of the disease by studying whether or not there is a correlation between changes in their level and response to therapy with systemic steroid.

Methods:

Antibodies to the 40 to 45 kD, 75 kD, and 90 kD vitiligo antigens were measured prior to and following systemic steroid therapy in 10 patients with active vitiligo.

Results:

Four months following initiation of therapy, seven (78%) of nine patients with good clinical response to steroid treatment had a significant decrease in the level of vitiligo antibodies. By contrast, one patient who had no response to treatment had a slight increase in antibody levels.

Conclusion:

These findings suggest that one mechanism by which corticosteroids can cause repigmentation in vitiligo is by decreasing the level of vitiligo antibodies, and support the notion that vitiligo antibodies are involved in the pathogenesis of this disease.

The role of systemic steroids and phototherapy in the treatment of stable vitiligo: a randomized controlled trial

Pathogenesis of vitiligo is believed to be multifactorial disease with a wide variety of therapeutic modalities. The aim of this work is to assess the efficacy of oral mini-pulse steroids (OMP) plus Nb-U.V.B in comparison to OMP alone and Nb-U.V.B alone in treating stable vitiligo. A prospective randomized controlled study including 45 patients categorized into three groups receiving therapy for 3 months; Group A received Nb-U.V.B plus OMP, Group B received OMP alone while Group C received Nb-U.V.B alone. Clinical assessment and PCR evaluation of bFGF, ICAM1, and ELISA for AMA were done. Patients receiving Nb-U.V.B plus OMP and using Nb-U.V.B alone gave statistically significant clinical response than those treated with OMP alone. Statistically significant rise of BFGF was noticed after treatment with Nb-U.V.B plus OMP and with Nb-U.V.B alone. Patients treated with OMP alone and with Nb-U.V.B alone showed statistically significant drop of ICAM-1 after therapy. NB-U.V.B plus OMP and Nb-U.V.B alone were found to be clinically superior over OMP alone in treating stable vitiligo patients, hence suggesting that adding OMP to Nb-U.V.B can maintain clinical and laboratory success for a longer period of time and with less relapse.

Low-Dose Oral Mini-Pulse Dexamethasone Therapy in Progressive Unstable Vitiligo

Background:

The course of vitiligo is unpredictable. If the disease is spreading rapidly, the progression can be controlled with the use of systemic steroids daily or in pulsed form. The present study was planned to assess the efficacy of low-dose dexamethasone oral mini-pulse therapy in progressive unstable vitiligo.

Materials and Methods:

In this retrospective study, the case records of patients with vitiligo during the period from January 2006 to December 2010 were studied. Patients who had progressive unstable disease were included. These patients were administered oral dexamethasone 2.5 mg per day on 2 consecutive days after breakfast in a week. The patients were asked to come for regular follow-up to assess the arrest of disease activity, relapse of disease activity, and adverse effects.

Results:

A total of 444 patients were analyzed. In 408 (91.8%) patients, arrest of disease activity was achieved at a mean duration of 13.2 ± 3.1 weeks. In addition, some repigmentation of the lesions was seen in all patients after a mean of 16.1 ± 5.9 weeks. During the follow-up, 50 of 408 (12.25%) patients experienced one or two episodes of relapse in disease activity, which were treated with reinstitution of low-dose dexamethasone oral mini-pulse therapy. The mean disease-free survival (DFS) until the first relapse was 55.7 ± 26.7 weeks, and the mean DFS until the second relapse was 43.8 ± 7.2 weeks. Adverse reactions such as weight gain, lethargy, and acneiform eruptions were observed in 41 (9.2%) patients.

Conclusion:

Low-dose oral mini-pulse dexamethasone therapy is a good option for arresting progressive unstable vitiligo with minimal adverse effects.

Vitiligo

Vitiligo, an acquired pigmentary disorder of unknown origin, is the most frequent cause of depigmentation worldwide, with an estimated prevalence of 1%. The disorder can be psychologically devastating and stigmatising, especially in dark skinned individuals. Vitiligo is clinically characterised by the development of white macules due to the loss of functioning melanocytes in the skin or hair, or both. Two forms of the disease are well recognised: segmental and non-segmental vitiligo (the commonest form). To distinguish between these two forms is of prime importance because therapeutic options and prognosis are quite different. The importance of early treatment and understanding of the profound psychosocial effect of vitiligo will be emphasised throughout this Seminar.

Elevated Serum Antimelanocyte Antibody Level in Cerebriform Intradermal Nevus with Vitiligo

We describe a rare, but typical case of cerebriform intradermal nevus associated with vitiligo. A 45-year-old man had a patch of alopecia over his vertex scalp for 15 years. The microscopic findings of the biopsy revealed a typical deep-seated intradermal nevus and neuroid differentiation with a few pigments. Three hypopigmented patches developed on the forehead, cheek and index finger five years after the scalp lesion, with loss of both melanocytes and melanins. In addition, no dopa reactions were present. Compared to normal controls, the serum anti-melanocyte antibody level in the patient was elevated as determined by cellular enzyme-linked immunosorbent assay (cellular ELISA). This is the first reported case with elevation of serum antimelanocyte antibody level of cerebriform intradermal nevus with vitiligo. This antibody's presence may be related to the occurrence of the vitiligo in patient with cerebriform intradermal nevus.

Profile of vitiligo in kumaun region of uttarakhand, India

Background:

Vitiligo is a common, acquired, pigmentary disorder characterized by loss of melanocytes resulting in white spots. This disease carries a lot of social stigma in India.

Objective:

To study the clinico-epidemiological profile of vitiligo patients in Kumaun region of Uttarakhand state in India.

Materials and Methods:

The clinical presentation of vitiligo was examined and analyzed in 762 vitiligo patients attending the Dermatology outdoor of Government Medical College, Haldwani, which is a referral centre for Kumaun region of Uttarakhand state in India.

Results:

Male and female patients were found to be affected almost equally. It was observed that onset of vitiligo was most common in 0-10 years age group, as evidenced by 336 cases out of 762 cases. Acrofacial type of vitiligo (339 cases out of 762) was most commonly observed, followed by vitiligo vulgaris, focal, segmental, mucosal, mixed, and universal vitiligo. The most common site of onset was the lower limbs followed by head and neck, upper limbs, trunk, genitalia, and mucasae. Leucotrichia was observed in 33.5%, Koebner's phenomenon in 26.3%, and a positive family history in 19% of the vitiligo patients. The other common conditions associated were thyroid disorders (8.9%), diabetes (5.3%), and atopic dermatitis (4.9%).

Conclusion:

The study indicates that acrofacial vitiligo is the most common clinical type observed in Kumaun region of Uttarakhand in India. Onset of vitiligo is most common in first decade of life.

Whole Transcriptome Analysis (RNA Sequencing) of Peripheral Blood Mononuclear Cells of Vitiligo Patients

Vitiligo is an idiopathic disorder characterized by depigmented patches on the skin due to a loss of melanocytes. The cause of melanocyte destruction is not fully understood. The aim of this study was to detect the potential pathways involved in the vitiligo pathogenesis to further understand the causes and entity of vitiligo. For that the transcriptome of peripheral blood mononuclear cells of 4 vitiligo patients and 4 control subjects was analyzed using the SOLiD System platform and whole transcriptome RNA sequencing application. Altogether 2,470 genes were expressed differently and GRID2IP showed the highest deviation in patients compared to controls. Using functional analysis, altogether 993 associations between the gene groups and diseases were found. The analysis revealed associations between vitiligo and diseases such as lichen planus, limb-girdle muscular dystrophy type 2B, and facioscapulohumeral muscular dystrophy. Additionally, the gene groups with an altered expression pattern are participating in processes such as cell death, survival and signaling, inflammation, and oxidative stress. In conclusion, vitiligo is rather a systemic than a local skin disease; the findings from an enormous amount of RNA sequencing data support the previous findings about vitiligo and should be further analyzed.

Stability in Vitiligo: Is there a Perfect Way to Predict it?

Stability is a hard-to-define concept in the setting of vitiligo, but is nonetheless extremely crucial to the planning of treatment regimens and also in prognosticating for the patient. There are several ways to judge stability in vitiligo, which include clinical features and, recently, many biochemical, cytological and ultrastructural correlates of the same. These recent advances help in not only in prognosticating individual patients but also in elucidating some of the mechanisms for the pathogenesis of vitiligo, including melanocytorrhagy and oxidative damage to melanocytes.

When are laboratory tests indicated in patients with vitiligo?

Background: Vitiligo has been associated with multiple endocrine and immune conditions. Several laboratory tests have been assessed in this disease with controversial results.

Objective: The aim of this study is to analyze the levels autoantibodies, basal glycaemia, vitamin B12, folic acid and thyroid function and its association with the diagnosis and outcome of vitiligo patients through a case-control study.

Material and methods: This case-control study was performed on 196 consecutive patients with vitiligo referred to our Dermatology Department. As a control group, 160 healthy individuals without vitiligo or known history of immunologic/endocrine disease were included. Data were analyzed using the SPSS 17.0 statistical software package.

Results: Clinical, analytical and demographic data have been recorded. Our results showed that anti-thyroid peroxidase antibody and anti-parietal gastric cell antibody could be useful laboratory markers in a subpopulation of vitiligo patients. However, testing anti-nuclear antibody, anti-thyroglobulin antibody, folic acid and vitamin B12 seems to have limited clinical implication and diagnostic relevance in our routine clinical practice.

Limitations: This study addressed a selected population of vitiligo patients in Spain and may not generalize to different clinical settings or regions. The study of a wider sample would confirm these findings and allow a detailed analysis of the above factors as a function of the clinical subtype of vitiligo.

Conclusion: We have determined the more efficient serological markers to order in vitiligo patients. Our findings suggest that anti-thyroid peroxidase antibody and anti-parietal gastric cell could be useful tests for the characterization of specific subpopulations of vitiligo patients in terms of severity and co-morbidity, so their determination could have a prognostic value.

Revised classification/nomenclature of vitiligo and related issues: the Vitiligo Global Issues Consensus Conference

During the 2011 International Pigment Cell Conference (IPCC), the Vitiligo European Taskforce (VETF) convened a consensus conference on issues of global importance for vitiligo clinical research. As suggested by an international panel of experts, the conference focused on four topics: classification and nomenclature; definition of stable disease; definition of Koebner's phenomenon (KP); and 'autoimmune vitiligo'. These topics were discussed in seven working groups representing different geographical regions. A consensus emerged that segmental vitiligo be classified separately from all other forms of vitiligo and that the term 'vitiligo' be used as an umbrella term for all non-segmental forms of vitiligo, including 'mixed vitiligo' in which segmental and non-segmental vitiligo are combined and which is considered a subgroup of vitiligo. Further, the conference recommends that disease stability be best assessed based on the stability of individual lesions rather than the overall stability of the disease as the latter is difficult to define precisely and reliably. The conference also endorsed the classification of KP for vitiligo as proposed by the VETF (history based, clinical observation based, or experimentally induced). Lastly, the conference agreed that 'autoimmune vitiligo' should not be used as a separate classification as published evidence indicates that the pathophysiology of all forms of vitiligo likely involves autoimmune or inflammatory mechanisms.

The concept of stability of vitiligo: a reappraisal

Stability is taken as the most important parameter before opting for any transplantation technique to treat vitiligo. But, simultaneous donor site repigmentation and depigmentation of grafts at the recipient site has been noted. Similarly donor site depigmentation with complete repigmentation of the recipient area with pigment growing out from each graft has been observed. Successful repigmentation after regrafting in previous punch failure cases has also been reported. Koebner's phenomenon from history (Kp-h) and test grafting were the only available indicators to assess stability. It is quite ironic to note that even after four decades of experience in vitiligo surgery, there seems to be little consensus among workers regarding the optimal required period of stability. Moreover, the exact concept of stability in vitiligo is itself still not transparent and defined beyond doubt Overdependence on KpH or TG may be sometimes misleading in vitiligo. These two reveal the apparent clinical stability only and that may not be the true reflection of stability status of the disease at the molecular level. Antimelanocyte cytotoxic reactivity was observed among CD8+ TCC isolated from perilesional biopsies of patients with vitiligo. An attempt should be made to clearly fathom and define stability, not merely only on clinical ground but along with electron microscopy and histoenzymological analysis of the perilesional and nonlesional skin of vitiligo patients. Probably some growth factors which are responsible for both mitogenic and melanogenic stimulation of melanocytes should also be taken into account. Some serological test(s) could guide us to measure these growth factors.

IFN-γ, IL-21, and IL-10 co-expression in evolving autoimmune vitiligo lesions of Smyth line chickens

The Smyth line (SL) of chicken is an excellent animal model for human autoimmune vitiligo. In SL vitiligo (SLV), postnatal loss of melanocytes in feathers appears to be due to cell-mediated immunity. In this study, leukocyte infiltration and associated expression (RNA) of immune function-related cytokines in growing feathers were investigated throughout SLV development and progression. Both leukocyte infiltration and cytokine expression levels started to increase near visible SLV onset (early SLV), reached peak levels during active SLV, and decreased to near pre-vitiligo levels after complete loss of melanocytes. Specifically, significant increases were noticed in relative proportions of T cells, B cells, and major histocompatibility complex (MHC) II-expressing cells during active SLV. Levels of T-cell infiltration were higher than those of B cells, with more CD8+ than CD4+ cells throughout SLV. Elevated leukocyte infiltration in early and active SLV was accompanied by increased levels of cytokine expression, especially in IFN-γ, IL-10, and IL-21. Low expression of IL-4 and IL-17 did not suggest important roles of Th2 and Th17 cells in SLV pathogenesis. Taken together, SLV appears to be a Th1-polarized autoimmune disease, whereby IFN-γ expression is strongly associated with parallel increases in IL-10 and IL-21, particularly during early and active stages of SLV.

An uncommon presentation of the co-existence of morphea and vitiligo in a patient with chronic hepatitis B virus infection: is there a possible association with autoimmunity?

A 30-year-old man presented with indurated violaceous plaques all over his body that had been present for 7 months. The patient had also had vitiligo for 3.5 years, and hepatitis B virus (HBV) infection and cirrhosis for a 2-year period. Histopathologic examination of the indurated plaques confirmed the diagnosis of morphea. Localized scleroderma and vitiligo have only rarely been reported to occur simultaneously. Although the etiologies of vitiligo and morphea are both uncertain, their association with autoimmune diseases favors an autoimmune hypothesis. Both vitiligo and morphea might have appeared coincidentally. However, this association could be significant because it may be related to the presence of HBV and alterations in the immune system that are caused by this virus. Therefore, this rare combination of vitiligo and morphea in a patient with chronic HBV infection warrants attention because it suggests a possible immunologic association, which may merit future study.

The Double Strike Hypothesis of the vitiligo pathomechanism: new approaches to vitiligo and melanoma

Based on current research, we present a consolidated set of theses which explain the pathomechanisms of vitiligo- and melanoma-associated hypopigmentation. The main thesis is the Double Strike Hypothesis, i.e. vitiligo is caused by at least two different major pathomechanisms: an antibody-based pathomechanism and a T-cell-based pathomechanism. The antibody-based pathomechanism is dominant in diffuse vitiligo, while the T-cell based pathomechanism is dominant in localised vitiligo. Based on this main thesis we derive new therapeutical approaches to vitiligo and melanoma by using the different pathomechanisms. Finally we explain why melanoma-associated hypopigmentation as a natural immunotherapy is still in statu nascendi.

Psoralen and ultraviolet A and narrow-band ultraviolet B in inducing stability in vitiligo, assessed by vitiligo disease activity score: an open prospective comparative study

BACKGROUND

Vitiligo is a common pigmentary disorder with great cosmetic and psychological morbidity and an unpredictable course. No treatment available is a definitive cure. Systemic psoralen and ultraviolet A (PUVA) has been the mainstay of treatment. Narrow-band UVB (NBUVB) was later introduced. In this study, we have compared the phototherapy modalities PUVA and NBUVB in inducing stability in vitiligo, assessed by using vitiligo disease activity score (VIDA), for the first time.

AIMS

To investigate the position of NBUVB vis-à-vis PUVA in terms of stability achieved during therapy as indicated by the VIDA scores.

SUBJECTS AND METHODS

It was an open, prospective study of 50 patients divided equally in PUVA and NBUVB groups. The study period was from January 2004 to June 2005. This study was done as a part of a larger project to compare the efficacy of mentioned modalities in degree of repigmentation.

RESULTS

In the NBUVB group, disease activity was present in 40% patients before commencement of therapy, which was reduced to 16% at the end of therapy (statistically significant, P = 0.049). In the PUVA group, similar figures were 20% and 16%, respectively. In the NBUVB group, 50% of patients whose disease was active prior to commencement of therapy had less than 50% repigmentation, whereas an equal number of patients had repigmentation of more than 50%. Almost an equal number of stable patients had less than and more than 50% repigmentation. In the PUVA group, 4 of the 5 (80%) patients who had active disease had less than 50% repigmentation, whereas only 1 patient (20%) with active disease obtained more than 50% repigmentation. The time to attain stability was 3.6 +/- 2.1 months in the NBUVB group and 3.22 +/- 3.1 months in the PUVA group. Eight of the 10 (80%) patients with unstable disease in the NBUVB group achieved stability, whereas 2 of the 5 (40%) patients of similar pre-treatment status in the PUVA group achieved stability.

CONCLUSION

NBUVB was in a more statistically advantageous position vis-à-vis PUVA, in respect to stability achieved and efficacy in both active and stable disease in a comparable time period.

Effects of psoralen plus ultraviolet A irradiation on cultured epidermal cells in vitro and patients with vitiligo in vivo

BACKGROUND

Both psoralen plus ultraviolet (UV) A (PUVA) and narrowband UVB (NB-UVB) irradiation are effective treatments for vitiligo vulgaris. However, the mechanisms of PUVA and NB-UVB in repigmentation are not thoroughly clarified. Our previous results showed that NB-UVB irradiation directly promotes melanocyte (MC) migration and stimulates MC proliferation via keratinocytes (KCs).

OBJECTIVES

In the present study, we used NB-UVB as a reference for comparison to investigate the immediate effects of PUVA on MC proliferation and migration.

METHODS

Cultured MCs and KCs were treated with PUVA or irradiated with NB-UVB. The direct impact of PUVA treatment on MCs was assessed in terms of its effect on MC proliferation and migration. The indirect effect of PUVA treatment and NB-UVB irradiation on MC proliferation via KCs was also investigated. The activities of matrix metalloproteinase (MMP)-2 and MMP-9, known for their influence on cell migration, were evaluated in the PUVA-treated MC and KC supernatants. The concentrations of MC mitogens/growth factors in the PUVA-treated KC supernatants were also determined. In addition, the serum levels of MC mitogens/growth factors in healthy controls, in patients with active vitiligo and in patients with repigmenting vitiligo after PUVA treatment were determined to elucidate the mechanisms of how PUVA induces vitiligo repigmentation in vivo.

RESULTS

Our results demonstrated that PUVA treatment did not significantly stimulate the release of MC mitogens/growth factors from KCs. The migration of MCs was also not enhanced after PUVA treatment. The expression of MMP-2 activity in supernatants derived from PUVA-treated MCs was significantly increased as compared with the control group. However, neither MMP-2 nor MMP-9 activity in KC supernatants was stimulated by PUVA treatment. In contrast to NB-UVB, immediate effects of PUVA on MC proliferation and migration were not observed in this study. Sera from patients with repigmenting vitiligo after PUVA treatment contained higher levels of basic fibroblast growth factor, stem cell factor and hepatocyte growth factor as compared with healthy controls and patients with active vitiligo.

CONCLUSIONS

Our results indicate that in addition to immune suppression, PUVA treatment creates a favourable milieu for promoting the growth of MCs in patients with vitiligo instead of directly stimulating the regrowth of MCs. Based on our results, we propose that in the active stage of vitiligo, PUVA treatment is the therapy of choice to slow down the destruction of MCs and to create a favourable environment for MCs to survive. In the stable stage of vitiligo, NB-UVB irradiation should be used to stimulate the proliferation and migration of MCs directly.

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.

The effect of antisense tyrosinase-related protein 1 on melanocytes and malignant melanoma cells

BACKGROUND

Tyrosinase-related proteins (TRPs) include tyrosinase, TRP-1 and TRP-2. The functions of tyrosinase and TRP-2 have been determined, but the biological role of TRP-1 is still controversial and is not well known in humans.

OBJECTIVES

To study further the biological role of the human TRP-1 gene in melanocytes and melanoma cells.

METHODS

TRP-1 cDNA was subcloned into eukaryotic expression vector pcDNA3.1 in the reverse direction, and antisense recombinant vector was transfected into melanocytes and a melanoma cell line using Lipofectamine 2000. Positive cells were selected by geneticin. TRP-1 mRNA level was measured by reverse transcription-polymerase chain reaction (RT-PCR), and TRP-1 protein level by Western blot. Cell cycles were determined by flow cytometry, and the activity of tyrosinase was evaluated by L-DOPA reaction. Light microscopy, electron microscopy and flow cytometry were used to observe cell morphology and apoptosis. For in vivo assays, the antitumour activity of antisense TRP-1 against the malignant melanoma (MM) cell line, Libr, was evaluated in an animal-tumour model of subcutaneous tumours.

RESULTS

Positive transfected cells steadily expressed TRP-1 antisense RNA. RT-PCR and Western blot showed a low level of TRP-1 mRNA and TRP-1 protein, respectively. Cell cycles were blocked in the G1 stage, and the activity of tyrosinase decreased significantly (P < 0.01). Light and electron microscopy showed abnormal cell morphology, and apoptosis was detected. The neoplasia activity of antisense TRP-1-transfected MM cells was significantly lower than that of MM cells (P < 0.01).

CONCLUSIONS

TRP-1 plays an important role in the proliferation, morphology and tyrosinase activity of melanocytes and melanoma cells.

Modulation of the outcome and severity of hepadnaviral hepatitis in woodchucks by antibodies to hepatic asialoglycoprotein receptor

Viral hepatitis is frequently accompanied by humoral autoimmune responses toward both organ-nonspecific and liver-specific antigens, but contribution of these reactivities to liver injury remains unrecognized. Infection with woodchuck hepatitis virus (WHV) has been identified as a potent inducer of autoantibodies against asialoglycoprotein receptor (anti-ASGPR), a molecule essentially unique to hepatocytes that mediates clearance of desialylated serum proteins. In this study, we applied the WHV-woodchuck model of hepatitis B to examine the effect of experimentally elicited anti-ASGPR on the progression and the severity of WHV hepatitis in initially healthy animals immunized with the receptor and then infected with WHV and in woodchucks with ongoing chronic WHV hepatitis. The results implied that the induction of anti-ASGPR prior to WHV infection tends to modulate acute viral hepatitis toward chronic outcome and, in animals with established chronic WHV infection, exacerbates histologic severity of liver lesions. The findings also suggest that the liver compromised by chronic hepadnavirus infection might be prone to anti-ASGPR-directed complement-mediated hepatocellular injury and that this is associated with formation of the ASGPR-anti-ASGPR immune complexes on hepatocyte surface. In conclusion, the host's immune response mounted against a hepatocyte-specific autoantigen may modulate both the outcome and the severity of liver injury in viral hepatitis.

Epidemiology of vitiligo and associated autoimmune diseases in Caucasian probands and their families

Generalized vitiligo is an autoimmune disorder characterized by acquired white patches of skin and overlying hair, the result of loss of melanocytes from involved areas. The most common disorder of pigmentation, vitiligo occurs with a frequency of 0.1-2.0% in various populations. Family clustering of cases is not uncommon, in a non-Mendelian pattern suggestive of multifactorial, polygenic inheritance. We surveyed 2624 vitiligo probands from North America and the UK regarding clinical characteristics, familial involvement, and association with other autoimmune disorders, the largest such survey ever performed. More than 83% of probands were Caucasians, and the frequency of vitiligo appeared approximately equal in males and females. The frequency of vitiligo in probands' siblings was 6.1%, about 18 times the population frequency, suggesting a major genetic component in disease pathogenesis. Nevertheless, the concordance of vitiligo in monozygotic twins was only 23%, indicating that a non-genetic component also plays an important role. Probands with earlier disease onset tended to have more relatives affected with vitiligo, suggesting a greater genetic component in early onset families. The frequencies of six autoimmune disorders were significantly elevated in vitiligo probands and their first-degree relatives: vitiligo itself, autoimmune thyroid disease (particularly hypothyroidism), pernicious anaemia, Addison's disease, systemic lupus erythematosus, and probably inflammatory bowel disease. These associations indicate that vitiligo shares common genetic aetiologic links with these other autoimmune disorders. These results suggest that genomic analysis of families with generalized vitiligo and this specific constellation of associated autoimmune disorders will be important to identify the mechanisms of genetic susceptibility to autoimmunity.

Evidence for an autoimmune pathogenesis of vitiligo

Vitiligo is a depigmenting disorder characterized by the development of white patches in various distributions, which are due to the loss of melanocytes from the epidermis. A variety of arguments from clinical observations to research findings in human and animal models support the hypothesis of autoimmunity and are reviewed in this article. The association with autoimmune diseases and organ-specific autoantibodies is well known. Various effective treatment options have an immunosuppressive effect. Today the autoimmune pathogenesis of the disease has become a rapidly evolving field of research. Detection of circulating melanocyte antibodies in human and animal models implicates a possible role of humoral immunity. Histological and immunohistochemical studies in perilesional skin suggest the involvement of cellular immunity in vitiligo. Recently, T-cell analyses in peripheral blood further support this hypothesis. Interestingly, new insights in the association of vitiligo and melanoma may help to clarify the role of autoimmunity in the development of vitiligo.

Vitiligo: a manifestation of apoptosis?

Vitiligo is a common cutaneous disorder that has significant biological and social consequences for those affected. It is characterized by a loss of melanocytes from the epidermis, which results in the absence of melanin, i.e. depigmentation. There are numerous hypotheses about the etiology of vitiligo, but no data to definitively prove one theory over another. It is likely that there are numerous causes for the loss of these melanocytes. One way to approach the identification of the etiology is to determine the mechanism by which the melanocytes are destroyed. The two known mechanisms for the destruction of cells are necrosis and apoptosis. One purpose of this paper is to review the extant data that might suggest which of the two mechanisms is operative against melanocytes in patients with vitiligo. The histological data, and some laboratory data, support apoptosis, rather than necrosis, as the mechanism for removal of melanocytes. Apoptosis can be induced by a variety of factors, including immune cytokines, some environmental chemicals (for example substituted hydroquinones such as monobenzone) or other molecular mechanisms. Current therapies, such as corticosteroids and ultraviolet light, do affect apoptosis in a variety of ways. Confirmation of apoptosis as a mechanism, and identification of how apoptosis is initiated to produce vitiligo, can serve as a basis for devising medications that might stop the progression of the disorder. The problem of vitiligo would be essentially solved if there was a medication that is well tolerated in children, adults and pregnant women, and that would halt the progression of the depigmentation. The study of apoptosis, mechanisms of its induction, and the ways to block apoptosis, is one possible way to find both the causes of depigmentation and medications to prevent its progression.

Vitiligo. Pathogenesis and treatment

Vitiligo is an acquired skin disorder caused by the disappearance of pigment cells from the epidermis that gives rise to well defined white patches which are often symmetrically distributed. The lack of melanin pigment makes the lesional skin more sensitive to sunburn. Vitiligo can be cosmetically disfiguring and it is a stigmatizing condition, leading to serious psychologic problems in daily life. It occurs worldwide in about 0.5% of the population and it occurs as frequently in males as it does in females. The cause is unknown, but might involve genetic factors, autoimmunity, neurologic factors, toxic metabolites, and lack of melanocyte growth factors. Since a causative (gene) treatment is not (yet) available, current modalities are directed towards stopping progression and to achieving repigmentation in order to repair the morphology and functional deficiencies of the depigmented skin areas. Many treatments have been used for some time; however; there are some new developments: narrowband ultraviolet (UV) B (311 nm) therapy, the combination of corticosteroid cream + UVA therapy, and the transplantation of autologous pigment cells in various modalities. In widespread vitiligo, residual pigment can be removed by depigmentation agents. Sunscreens, camouflage products, and good guidance may help the patient cope better with the disease.

Specific cytotoxic T lymphocyte responses against Melan-A/MART1, tyrosinase and gp100 in vitiligo by the use of major histocompatibility complex/peptide tetramers: the role of cellular immunity in the etiopathogenesis of vitiligo

Vitiligo is a common skin disease characterized by the presence of well circumscribed, depigmented, milky white macules devoid of identifiable melanocytes. Although the detection of circulating anti-melanocytic antibodies and of infiltrating lymphocytes at the margin of lesions supports the view that vitiligo is an autoimmune disorder, its etiology remains unknown. In particular, it is still a matter of debate whether the primary pathogenic role is exerted by humoral or cellular abnormal immune responses. In this study, the presence of specific cytotoxic T lymphocyte responses against the melanocyte differentiation antigens Melan-A/MART1, tyrosinase, and gp100 in vitiligo patients have been investigated by the use of major histocompatibility complex/peptide tetramers. High frequencies of circulating melanocyte-specific CD8+ T cells were found in all vitiligo patients analyzed. These cells exerted anti-melanocytic cytotoxic activity in vitro and expressed skin-homing capacity. In one patient melanocyte-specific cells were characterized by an exceptionally high avidity for their peptide/major histocompatibility complex ligand. These findings strongly suggest a role for cellular immunity in the pathogenesis of vitiligo and impact on the common mechanisms of self tolerance.

Vitiligo melanocytes in long-term culture show normal constitutive and cytokine-induced expression of intercellular adhesion molecule-1 and major histocompatibility complex class I and class II molecules

The aetiology of vitiligo remains unclear. An autoimmune involvement has been suggested and, in this study, we examine whether melanocytes cultured from unaffected regions of the skin of vitiligo patients are more susceptible to immune attack by investigating constitutive and cytokine-stimulated expression of intercellular adhesion molecule-1 (ICAM-1) (under three media variants) and major histocompatibility complex (MHC) class I and class II (under one medium). Both normal and vitiligo melanocytes had similarly low constitutive expression of ICAM-1 and MHC class II molecules, whereas > 95% of cells had high constitutive expression of MHC class I. Normal and vitiligo melanocytes showed similar and significant increases in the expression of all three immune-related molecules in response to the cytokine, interferon-gamma. The expression of ICAM-1 was also similarly increased by the cytokine, tumour necrosis factor-alpha in both cells. Additionally, it was noted that, once the melanocyte cultures were established under experimental conditions, the rate of proliferation of vitiligo melanocytes did not differ significantly from that of normal melanocytes. In conclusion, we suggest that vitiligo melanocytes, once in culture, do not have intrinsic differences from normal melanocytes with respect to the expression of immune-related molecules.

Complement-mediated cytotoxicity and inhibition of ligand binding to hepatocytes by woodchuck hepatitis virus-induced autoantibodies to asialoglycoprotein receptor

Hepadnavirus invasion in woodchucks has been identified as a potent inducer of autoantibodies against asialoglycoprotein receptor (anti-ASGPR), a molecule essentially unique to hepatocytes that mediate clearance of desialylated serum proteins. We evaluated the possible pathogenetic importance of anti-ASGPR triggered by woodchuck hepatitis virus (WHV), using anti-ASGPR-reactive serum immunoglobulins (Igs) from five animals with different stages of WHV hepatitis or self-limited WHV infection and isolated woodchuck hepatocytes or HepG2 cells as targets. The results revealed that WHV-induced anti-ASGPR can specifically inhibit asialoglycoprotein recognition by both homologous and heterologous liver cells, as tested in an asialofetuin (ASFN)-binding radioassay. However, the extent of the interference significantly varied (from 85% inhibition to none) for anti-ASGPR with similar titer from different animals, indicating a high degree of heterogeneity in the ASGPR epitope specificity and in the potential biological effects of these autoantibodies. The WHV-triggered anti-ASGPR also induced complement-mediated hepatocytolysis in a microculture tetrazolium (MTT) assay, which ranged from 8.9% +/- 0.3% to 33.6% +/- 3.6% (mean +/- SD) for different animals and target cell numbers. This cytopathic effect was strictly ASGPR-specific, complement-dependent, and was not related to the anti-ASGPR ability to inhibit ligand-hepatocyte binding. Our findings indicate that among pathways by which anti-ASGPR autoimmunity could cause liver damage, hepadnavirus-induced anti-ASGPR might impair hepatocytes by both disrupting clearance of desialylated proteins and activation of the complement-mediated cytolysis. These cytopathic effects might contribute to the pathogenesis, aggravate severity, and prolong recovery from liver injury in viral hepatitis.

Relative contributions of decay accelerating factor (DAF), membrane cofactor protein (MCP) and CD59 in the protection of melanocytes from homologous complement

Complement regulatory molecules, membrane cofactor protein (MCP), decay accelerating factor (DAF) and CD59, protect body cells from autologous complement. They have wide tissue distribution but nothing is known about the expression of these molecules on human melanocytes. Since melanocytes are lysed in the lesional skin of patients with a depigmentary disorder vitiligo, it is important to compare the protection offered by complement regulatory molecules to melanocytes present in normal and vitiligo epidermis, against autologous complement. From this point of view, we investigated the differential expression of MCP, DAF and CD59 on normal cultured human melanocytes and assessed their individual contribution in the protection of these cells against complement-mediated damage. Flow cytometric analysis showed that MCP and DAF but not CD59 were expressed on cultured melanocytes. When heat inactivated sera of patients with vitiligo were used as a source of anti-melanocyte antibody to sensitize melanocytes, and guinea pig serum (GpS) or normal human serum (NHS) as a source of complement, GpS was found to be more effective in causing the lysis of melanocytes than NHS. When melanocytes were sensitized with autoantibody as well as F(ab')2 fragment of either anti-MCP or anti-DAF and subsequently incubated with NHS or GpS, both antibody fragments increased the killing of melanocytes by NHS as well as by GpS. F(ab')2 fragment of anti-DAF was much more effective in causing enhancement of lysis than that of anti-MCP. Thus, cultured normal human melanocytes express functionally active MCP and DAF but not CD59. Contribution of DAF in protecting melanocytes against complement attack was much more than that of MCP.