Analysis of major histocompatibility antigens and the mononuclear cell infiltrate in halo nevi

A similar local immune and oxidative stress phenotype in vitiligo and halo nevus

BACKGROUND

Vitiligo and halo nevus are two common T-cell-mediated skin disorders. Although autoimmunity has been suggested to be involved in both diseases, the relationship between vitiligo and halo nevus is not fully understood.

OBJECTIVE

The aim of the current study was to investigate whether vitiligo and halo nevus share the same immunological and oxidative stress response.

METHODS

Infiltrations of T cells, and expressions of chemokine receptors (CXCR3, CCR4, CCR5) and cytotoxic markers (Granzyme B, Perforin) in the lesions of vitiligo and halo nevus were examined by immunohistochemistry. Enzyme-linked immunosorbent assay was performed to analyze the expressions of chemokines in the serum samples and cytotoxic markers secreted by CD8⁺ T cells which were sorted from the peripheral blood mononuclear cells in healthy donors, vitiligo and halo nevus patients. Tissue levels of chemokine receptors and CXCR3 ligands in healthy controls, vitiligo patients and halo nevus patients were determined by qRT-PCR analysis. The percentages of CXCR3⁺ CD4⁺ T and CXCR3⁺ CD8⁺ T cells from the peripheral blood samples were examined by flow cytometry. Tissue and serum hydrogen peroxide (H₂O₂) concentrations were measured using H₂O₂ assay kit.

RESULTS

Immunohistochemistry revealed a significant T-cell response, with pronounced dermal infiltrates of CD8⁺ T cells in vitiligo and halo nevus. The inflammatory cytotoxic markers such as Granzyme B and Perforin were also elevated in vitiligo and halo nevus, suggesting inflammatory responses in situ. By qRT-PCR and ELISA assay, we found significantly increased expressions of the chemokine receptor CXCR3 and its ligands, especially the accumulated CXCL10 in the skin lesions of vitiligo and halo nevus. Moreover, the level of H₂O₂, a key player involved in regulation of the immune response was significantly upregulated in the skin lesions of vitiligo and halo nevus. In addition, the increased H₂O₂ concentration correlated positively with CXCL10 level in skin lesions of vitiligo and halo nevus.

CONCLUSIONS

These results demonstrate a H₂O₂-involved autoimmune phenotype in vitiligo and halo nevus, characterized by increased level of IFN-γ-inducible chemokine pair CXCL10-CXCR3, as well as a dense CD8⁺ T infiltration in the skin lesions, thus suggesting a similar pathogenesis of the two diseases.

Foxp3(+) regulatory T cells are increased in the early stages of halo nevi: clinicopathological features of 30 halo nevi

BACKGROUND

There have been few clinical studies of the role of regulatory T cells (Tregs) in halo formation of halo nevus.

OBJECTIVE

To evaluate the clinicopathologic features and the presence of Tregs in halo nevi.

METHODS

We analyzed 30 halo nevi and performed immunohistochemical analysis using antibodies against CD4, CD8, CD25 and Foxp3. We also performed double immunohistochemical staining for Foxp3 and CD25.

RESULTS

We found significant increases in Foxp3(+) Tregs, and the shorter the halo nevus duration, the more Foxp3(+) Tregs were detected. Also, the ratio of Foxp3 to CD8 T cells was increased in early stages of halo nevi. Double immunohistochemical staining suggested that the Tregs in the halo nevi were CD25(+)Foxp3(+) T cells.

CONCLUSIONS

Foxp3(+) Tregs were greatly increased in the halo nevi. The shorter the halo nevi duration, the more Foxp3(+) Tregs were involved in the earlier developmental stages of halo nevi.

HLA antigen expression in melanocytic lesions: is acquisition of HLA antigen expression a biomarker of atypical (dysplastic) melanocytes?

BACKGROUND

Although criteria are established for the histologic diagnosis of atypical nevi (AN), consensus about the criteria in the diagnosis of and in the definition of AN is limited. Moreover, intraobserver and interobserver differences in the application of these criteria for the diagnosis of AN have been observed.

OBJECTIVE

We sought to determine the usefulness of HLA antigen expression as a biomarker of AN.

METHODS

The immunoperoxidase reaction was used to mark common nevi and AN with HLA class I heavy chain-, β2microglobulin (β2m)-, and HLA class II β chain-specific monoclonal antibodies.

RESULTS

HLA class I heavy chain, β2m, and HLA class II β chain were expressed in 5 (8.6%) of the 58 common nevi and in 46 (∼72%) of the 64 atypical melanocytic lesions. Among common lesions, only halo nevi expressed HLA class I heavy chain, β2m, and HLA class II β chain. The level of HLA class I heavy chain β2m and of HLA class II β chain expression correlated with the degree of cytologic atypia and architectural disorder.

LIMITATIONS

The number of lesions tested and the subjective nature of the analysis of immunohistochemical staining of tissue sections are both limitations.

CONCLUSIONS

The data presented suggest that HLA antigen expression is an objective biomarker that correlates well with the degree of cytologic atypia in AN and may: (1) be useful to distinguish common nevi from AN, and (2) represent a more objective measure to determine which AN should be excised.

Association of halo nevus/i and vitiligo in childhood: a retrospective observational study

BACKGROUND

Although halo nevus (HN) is frequently observed, the relationship between vitiligo and HN in children has rarely been investigated.

OBJECTIVES

To investigate the association between HN and vitiligo in children and understand if HN/HNi might be a risk factor for vitiligo.

METHODS

Ninety-eight patients with only HN/HNi and 27 with HN/HNi and vitiligo were investigated for number and localization of HN/HNi, family history for HN/HNi and vitiligo and personal and family history for autoimmune or other diseases. A follow-up telephone interview was performed to investigate the evolution of HN/HNi and the possible onset of vitiligo and/or other diseases.

RESULTS

In the HN/HNi and vitiligo group, HN/HNi and vitiligo had started almost simultaneously in 11 children; in nine, the onset of HN/HNi was followed by vitiligo after 6 months to 5 years; seven patients presented vitiligo first and HN/HNi after 3-9 years. Patients with associated vitiligo had, significantly more often, multiple HNi and a positive personal and/or family history of autoimmune thyroiditis compared with those with only HN/HNi. Follow-up longer than 5 years was available in 54/98 patients with only HN/HNi; two of them, both with multiple HNi, developed vitiligo. After follow-up, multiple HNi were noticed in 18/52 patients without vitiligo and in 9/11 of those in whom HN/HNi heralded vitiligo (s.s.).

CONCLUSIONS

In patients with multiple HNi, the risk of vitiligo and other autoimmune diseases seems to be higher than in pediatric patients with a single HN; clinicians should pay particular attention to children with multiple HNi and personal or family history of autoimmune diseases.

[Complete regression of melanocytic nevi: correlation between clinical, dermoscopic, and histopathologic findings in 13 patients]

BACKGROUND

The complete regression of melanocytic tumors, confirmed by histology, has rarely been reported in the literature. It is very difficult to determine the malignant or benign nature of a regressed tumor, and on occasions, the only indication of malignancy is the subsequent development of metastasis.

MATERIAL AND METHODS

We performed a descriptive study of melanocytic nevi that had undergone complete, histologically confirmed regression prior to excision in the dermatology department of our hospital over a period of 3 years. We included only lesions in which dermoscopy performed prior to regression showed features that suggested benignity. We assessed various clinical, dermoscopic, histologic, and immunohistochemical features.

RESULTS

The mean time to complete regression was 6.4 months. The main dermoscopic patterns observed were reticular and mixed reticular/globular. Unlike what is generally seen in melanomas, the main histologic finding was the presence of fine or lamellar fibrosis. In all cases, there was a predominance of CD8+ T cells.

CONCLUSIONS

The clinical, dermoscopic, and histologic features of the melanocytic nevi studied suggest the existence of a highly characteristic form of tumor regression characterized by very rapid regression and the involvement of a cytotoxic mechanism.

HLA antigen and NK cell activating ligand expression in malignant cells: a story of loss or acquisition

Malignant transformation of cells is often associated with changes in classical and non-classical HLA class I antigen, HLA class II antigen as well as NK cell activating ligand (NKCAL) expression. These changes are believed to play a role in the clinical course of the disease since these molecules are critical to the interactions between tumor cells and components of both innate and adaptive immune system. For some time, it has been assumed that alterations in the expression profile of HLA antigens and NKCAL on malignant cells represented loss of classical HLA class I antigen and induction of HLA class II antigen, non-classical HLA class I antigen and/or NKCAL expression. In contrast to these assumptions, experimental evidence suggests that in some cases dysplastic and malignant cells can acquire classical HLA class I antigen expression and/or lose the ability to express HLA class II antigens. In light of the latter findings as well as of the revival of the cancer immune surveillance theory, a reevaluation of the interpretation of changes in HLA antigen and NKCAL expression in malignant lesions is warranted. In this article, we first briefly describe the conventional types of changes in HLA antigen and NKCAL expression that have been identified in malignant cells to date. Second, we discuss the evidence indicating that, in at least some cell types, classical HLA class I antigen expression can be acquired and/or the ability to express HLA class II antigens is lost. Third, we review the available evidence for the role of immune selective pressure in the generation of malignant lesions with changes in HLA antigen expression. This information contributes to our understanding of the role of the immune system in the control of tumor development and to the optimization of the design of immunotherapeutic strategies for the treatment of cancer.

Fibrosis in regressing melanoma versus nonfibrosis in halo nevus upon melanocyte disappearance: could it be related to a different cytokine microenvironment?

BACKGROUND

It is not clear why melanocyte disappearance occurs without fibrotic evolution in halo nevus and with fibrotic evolution in regressing melanoma.

METHODS

Six halo nevi, seven regressing primary melanomas, and seven primary melanoma (PM) without regression were studied using immunohistochemistry for the phenotype of inflammatory infiltrate and the expression of cytokines involved in fibrogenesis or macrophage regulation. Melanocytes were also evaluated using electron microscopy.

RESULTS

CD8(+) lymphocytes predominated in halo nevus, whereas CD4(+) lymphocytes prevailed in melanoma; a few macrophages were only found in melanoma. Fibrogenic cytokines, IL-6, platelet-derived growth factor, and transforming growth factor-beta were only expressed in melanoma, whereas basic fibroblastic growth factor was also expressed in halo nevus. Antifibrotic cytokine tumor necrosis factor (TNF)-alpha was expressed at a higher degree in halo nevus. Cytokines involved in macrophage regulation were only expressed in melanoma.

CONCLUSIONS

Fibrogenic cytokines were more frequently expressed in melanoma than in halo nevus, irrespective of regression. At ultrastructural level, melanocytes showed a more activated status in regressing melanoma than in halo nevus, in compliance with a milieu richer in cytokines. Although the cytokine microenvironment does not completely justify the fibrotic evolution in regressing PM, the higher TNF-alpha expression in halo nevus suggests a possible role in nonfibrotic evolution of this lesion.

Completely regressed primary cutaneous malignant melanoma with nodal and/or visceral metastases: a report of 5 cases and assessment of the literature and diagnostic criteria

BACKGROUND

Partial regression of primary cutaneous malignant melanoma is not uncommon and may predict a higher likelihood of metastasis and decreased survival. Complete histologic regression of a primary cutaneous melanoma is a rarer occurrence, with only 34 cases reported in the English-language or English language-summarized literature.

OBSERVATION

We detail 4 cases of complete histologic regression of primary cutaneous melanoma, discovered at presentation with metastatic disease. A pigmented lesion or its remnant, coupled with historical information, was strongly suggestive of cutaneous melanoma. Histologic examination of the lesions, using multiple levels and immunohistochemical stains, failed to reveal residual melanoma. Our cases are typified by the presence of metastasis of melanoma to regional lymph nodes, with the absence of other suspect skin lesions or malignancies. In addition, we present a fifth case involving a completely regressed lesion on the scalp in a patient with cerebral melanoma metastasis and comment on the implications of this case to accepted diagnostic criteria, proposing that consideration of modification to the criteria be entertained.

CONCLUSION

The concept of completely regressed primary cutaneous melanoma is reviewed and the literature critically appraised. When one considers a diagnosis of completely regressed primary cutaneous melanoma, cases must be well documented and biopsy proven. Patients with metastatic melanoma and an occult primary lesion require a thorough skin examination, with serious consideration given to the possibility of completely regressed cutaneous melanoma.

Unusual inflammatory and hyperkeratotic halo naevus in children

Although the classic halo naevus (HN) is a melanocytic naevus with a surrounding rim of depigmentation, these naevi can present unusual features. We describe an unusual and previously unreported variety of HN in children. Between March 1999 and September 2002, 14 children (11 boys and three girls, age range 6-14 years) were referred to us for evaluation of one or more 'inflamed' naevi. All the affected naevi showed the same clinical development: (i) after an initial inflammatory stage their surfaces gradually became thickened and rough, then (ii) verrucous and raised, and finally (iii) scaly crusted. A marked halo of depigmentation subsequently developed in all lesions, with simultaneous disappearance of the hyperkeratotic surface appearance. Lesions were multiple in five cases and single in nine, and were mainly located on the back (nine cases). Excisional biopsy was performed in eight cases. The biopsies were all taken in the 'prehalo phase'. In each case, histopathology revealed a compound melanocytic naevus, with additional features that varied depending on the clinical stage of the lesion. Immunohistochemical staining of the dense inflammatory infiltrate showed a predominance of CD3(+)/CD8(+) T lymphocytes, as usually occurs in HN. On the basis of these observations, we believe that the described naevi represent an unusual variety of HN in children. Knowledge of this possible clinical evolution of HN is important to avoid unnecessary surgical excision in these young patients.

Proliférations mélanocytaires de l’enfant

Melanocytic nevi in children can be acquired or congenital. The vast majority are benign but diagnosis can be difficult. Nevi in newborns and nodular proliferations in giant congenital nevi can display histological features that lend to their misdiagnosis as melanoma. Acquired melanocytic nevi in children are often Spitz nevi or related nevi. These lesions are too often misdiagnosed as melanoma. On the other hand, clinicians and pathologists must be aware that melanoma does occur in childhood, albeit very rarely. It is exceptionally rare in prepubescent individuals. It can be associated with the following risk factors: giant congenital nevus, family history of melanoma, xeroderma pigmentosum, and immunosuppression. Melanoma in children younger than 10 years of age is extremely rare and has different clinical and histopathological features than those that arise in postpubescents, often being confused with a Spitz's nevus. Consequently, the diagnosis is often made too late. It should be emphasized that thickness is the main prognostic parameter in childhood melanoma and that early diagnosis is also crucial in this age group. The lesion must therefore be examined in a complete excision and not in a partial biopsy, and if atypical features are present it must be reviewed by an expert. On the other hand extreme caution should be exercised when diagnosing melanoma in children, as some benign lesions exhibit similar histologic features.

Difference in Pathogenesis Between Vitiligo Vulgaris and Halo Nevi Associated with Vitiligo is Supported by an HLA Association Study

Human leukocyte antigen (HLA) class II associations with two subtypes of vitiligo: vitiligo vulgaris and halo nevi associated with vitiligo were investigated. In previous studies associations between vitiligo and HLA antigens have been reported but these two subtypes have never been taken into account. However from a clinical and histological point of view, a difference in (auto)-immune pathogenesis can be expected. This difference might be reflected in an association with different HLA alleles. Seventy-six unrelated Dutch Caucasians, 40 with vitiligo vulgaris and 36 with halo nevi associated with vitiligo were included. A panel of randomly chosen HLA typed healthy Dutch blood donors (n = 2400) served as control population. HLA-DR and -DQ typing was carried out on blood samples by amplifying genomic DNA using polymerase chain reaction followed by dot blot hybridization with sequence specific oligonucleotides. The main outcome measures were odds ratio (OR), uncorrected P-value (P(u)) and corrected P-value. There were distinct differences in the clinical manifestations between vitiligo vulgaris and halo nevi associated with vitiligo with respect to precipitating factors, extent and progress of the disease and the association with other auto-immune diseases in the two subtypes and their respective first degree family members. Our stratification reveals differences in HLA class II between both subtypes and between subtypes and controls. A case-control association study showed a significant positive association of HLA-DR4 (OR = 2.787, P(u) = 0.0022) and DR53 (OR = 2.249, P(u) = 0.0153) and a negative association of HLA-DR3 (OR = 0.195, P(u) = 0.0024) with vitiligo vulgaris. The group with halo nevi associated with vitiligo did not show these associations, but had a significant negative association with HLA-DR11 (OR = 0.083, P(u) = 0.0067). In conclusion, the differences in HLA association within clinical subtypes of vitiligo support our suggestion that vitiligo vulgaris and halo nevi associated with vitiligo have distinct pathogenic mechanisms.

The immune response in halo nevi

The mechanism(s) responsible for halo nevus presents a provocative link with the immune response to melanoma. Although no direct demonstration of melanocyte killing has been observed by the immune effector cells found within the halo, the abundance of antigen-presenting cells in the regressing nevus and the presence of T lymphocytes at the site of depigmentation suggest that these cells participate in the halo phenomenon. Within the latter population of cells, evidence points to the involvement of CD8+ T cells as potential effectors in the destruction of nevomelanocytes. The break in tolerance that triggers migration and the presumed activation of these and other lymphocytes in the nevus in the apparent absence of disease remains unexplained. This brief overview reviews the evidence for the participation of the immune response in the genesis of the halo nevus.

Eczematous halo reaction in atypical nevi

Meyerson's nevus has been described as a melanocytic nevus with an associated eczematous halo reaction. We describe four patients with eczematous halos developing around atypical nevi, a finding not previously reported. Biopsy specimens revealed eosinophilic spongiosis in addition to the previously reported spongiotic dermatitis.

Halo nevus or halo phenomenon? A study of 142 cases

One hundred and forty-two (142) halo nevi were reviewed. For 66 cases the diagnosis of halo nevus was made both clinically and pathologically, and for 76 cases the diagnosis was based on histological grounds alone. The nevi were classified by type and by degree of atypia. Of the 142 nevi, all were compound, junctional, or intradermal nevi except for one case of a Spitz nevus and two cases that could not be further classified. For those with a clinicopathological diagnosis of halo nevus, 11% exhibited moderate atypia; 16% exhibited minimal atypia to only focally moderate atypia; 24% minimal atypia; and 49% exhibited no significant atypia. For those cases where the diagnosis was pathological only, there was also a broad spectrum of atypia identified, with 8% exhibiting focally severe or severe atypia. This study supports the concept that the halo nevus should not be regarded as a single clinicopathological entity, but rather that the halo phenomenon occurs in a wide spectrum of nevus types exhibiting a wide spectrum of histological atypia. The pathologist is therefore encouraged to classify halo nevi on the basis of the nevus cell population alone, using whatever classification normally utilized.

Characterization of the mononuclear infiltrate involved in regression of halo nevi

Halo nevi are characterized by progressive degeneration of nevus cells surrounded by a mononuclear cell infiltrate. We studied the morphological features of the nevus cells and the composition of the mononuclear cell infiltrate in 15 cases of halo nevi using immunohistochemical techniques and a battery of antibodies to different subsets of lymphocytes and histiocytes. Regression could be divided into four more or less identifiable stages, associated with different subsets of lymphocytes and monocyte-macrophage lineage cells. Stage I (preregression): nests of unremarkable nevus cells were surrounded by a moderate number of T lymphocytes (relatively small percentage of helper inducer T cells), occasional B cells and macrophages. Stage II (early regression): large number of T lymphocytes and FXIIIa-positive cells were in close contact with nevus cell clusters which showed ragged edges. Lysozyme-positive cells and epidermal Langerhans cells were mildly increased. Stage III (late regression): single nevomelanocytes showing mild atypia were present. Numerous T lymphocytes and macrophages positive for lysozyme, KP1 and/or FXIIIa were interspersed between the nevus cells. Increased numbers of epidermal Langerhans cells were present. Stage IV (complete regression): no nevus cells were observed and moderate numbers of T lymphocytes only remained. These results suggest that T cells, especially T-suppressor cells, and different subsets of macrophages participate in the regression of the nevi.

Halo dermatitis in children

Halo dermatitis is a pruritic, eczematous eruption on pigmented nevi and halo nevi in young adults. It may be mistaken for nummular eczema, psoriasis, or fungal skin infection. Awareness of halo dermatitis will possibly reveal more cases in children, which have been reported only rarely.

Congenital melanocytic nevi with halo phenomenon: report of two cases and a review of the literature

Verrucous congenital nevocellular nevi surrounded by a depigmented halo occurring in a 7-year-old boy and a 13-year-old girl were excised and the wounds closed primarily. Histopathologic studies revealed a striking arrangement of the inflammatory infiltrate in these halo nevi. A dense, band-like, lymphohistiocytic infiltrate was found only around and intermingled with A- and B-type nevomelanocytes in the upper dermis, whereas inflammatory infiltrates were completely absent from type C-nevomelanocytes in the lower parts of the reticular dermis. The literature is reviewed with particular consideration of congenital halo nevi.

Beta 2 microglobulin expression in normal melanocytes, nevocellular nevi, and malignant melanomas

Expression of beta 2 microglobulin (beta 2M), a light chain of class 1 HLA antigen, was studied in normal melanocytes and in benign and malignant melanocytic tumors by use of immunohistochemical methods. By immunoelectron microscopy, normal melanocytes were shown to express beta 2M on the cell surface. In lentigo maligna melanomas and acral lentiginous melanomas, the mean percentages of beta 2M-positive tumor cells were significantly lower in thick (greater than 1.50 mm) primary lesions and metastases than in thin (less than or equal to 1.50 mm) primary lesions. The evidence suggests that melanocyte-derived melanoma clones with a low grade of malignancy preserve class 1 HLA expression, and that the clones with a high grade of malignancy tend to lose the antigen expression. Nevus cells in common nevi have little or no expression of beta 2M. In halo nevi, however, beta 2M were detected on nevus cells in the lesions associated with inflammatory infiltration. Immunohistochemical analyses of the cellular composition of the inflammatory cells in halo nevi demonstrated the presence of cytotoxic T cells together with helper/inducer T cells, Langerhans cells, and macrophages. It appears that nevus cells of halo nevi are destroyed by cytotoxic T cells and that class 1 HLA antigens expressed on nevus cells play an important role in the target cell recognition and lysis by specific cytotoxic T cells.

Phenotypic expression of histocompatibility antigens in human primary tumours and metastases

HLA class I and II expression was studied on 244 (177 primary and 67 metastatic) solid human tumours of different origin. Alkaline immunophosphatase (APAAP) and immunoperoxidase were used on cryostatic sections to stain MHC antigens. Monomorphic MoAbs were used against class I heavy chain, beta 2-microglobulin, DR, DQ and DP molecules. Class I expression was homogeneous on colon, melanoma and epidermoidal primitive tumours. Loss of HLA class I antigens was more frequent on basal cell carcinomas and sarcomas and was related to tumour differentiation on larynx carcinoma. Class I expression was heterogeneous on breast, larynx and stomach primitive neoplasias. Class I negative tumours were more frequent on metastatic than on primitive melanomas. Divergence of class I between primary tumours and autologous metastases was observed on melanomas, larynx and colorectal carcinomas. Class II expression was heterogeneous on all tumours and in a large number of cases was associated with high intensity of leukocytic infiltrate. HLA-DR expression was higher than HLA-DP and HLA-DQ (DR greater than DP greater than DQ) and was related to tumour progression. Four human tumour cell lines were modulated with recombinant interferon-gamma for HLA class I and II antigens. Different HLA profiles were obtained: increased class I and II expression, increased class II or a low response. Finally, class I genes from 22 tumours were compared with autologous normal cells by Southern blot analysis: 12 tumours were class I positive and 10 negative. No clear differences in RFLP were observed that could be associated with class I rearrangement. The results are discussed in relation to the role that histocompatibility antigens may play in tumour progression and invasiveness.

Melanocytic atypia in dysplastic nevi. Immunohistochemical and cytophotometrical analysis

In a double-blind study a correlation was found between the histologically assessed degree of nevomelanocytic atypia in 58 dysplastic nevi (DN) and the presence of two markers associated with malignant transformation. The markers included a marked expression of histocompatibility locus Class I antigens on nevomelanocytes (P less than 0.01) and abnormalities in the nuclear DNA content as measured by DNA cytophotometry (P = 0.01). Both markers were present in most of the markedly atypical DN, in about half of the moderately atypical DN, and in less than 30% of the mildly atypical DN. These findings suggest that a DN with marked or moderate melanocytic atypia indicates a premalignant condition and identifies a patient at risk for melanoma.

Clinical features and course of type A and type B vitiligo

Four hundred and eighty one cases of vitiligo (acquired idiopathic depigmentation) were studied clinically. They were divided into two types, type B, in which depigmented patches are confined to a definite dermatome in the same manner as herpes zoster, and type A, which included all cases of vitiligo not classified as type B. The ratio of type A:type B was approximately 3:I. Onset of type A vitiligo could occur at any age, whereas type B generally affected the young. The activity of type B vitiligo usually ceased after one year, following rapid spread over the particular dermatomal area. However, in type A vitiligo new depigmented patches continued to appear throughout the patients' lives. Association with halo naevus and Köbner's phenomenon were observed exclusively in type A. Association with diseases with a proven or suggested allergic or immunological aetiology was more often found in type A. These findings support our hypothesis that type A and type B vitiligo have a different pathogenesis and that autoimmune mechanisms play a role only in type A.

Multiple agminate Spitz naevi: review of the literature and report of a case with distinctive immunohistological features

We describe a 13-year-old girl with multiple pigmented nodules and plaques arranged in a cluster in the right lumbar region, which had developed since infancy. Eleven of 15 lesions which were examined histologically were found to be Spitz naevi. The remaining four lesions were compound naevocellular naevi, and two of them showed focal dysplasia. Eight Spitz naevi were investigated immunohistologically with monoclonal antibodies against HLA-antigens and malignancy-associated melanocytic antigens which are rarely present in common naevi. Naevus cells in all lesions expressed HLA-ABC antigens, but lacked HLA-DR antigens in seven of the eight lesions. All naevi were positive for 'constitutive' (KG-6-56) and 'early' (K-1-2) markers of naevomelanocytic cells. In five of the eight Spitz naevi, at least one of the three malignancy-associated melanocytic antigens PAL-M1, A-1-43 and A-10-33 was found. The expression of malignancy-associated antigens in multiple agminate Spitz naevi is at variance with their benign clinical course.

Expression and susceptibility to modulation by interferons of HLA class I and II antigens on melanoma cells. Immunohistochemical analysis and clinical relevance

Immunohistochemical analysis for non-polymorphic determinants of HLA class I or class II antigens has been greatly facilitated by the use of monoclonal antibodies. Studies on the distribution of these antigens in tumour lesions emphasize their role in the tumour-host interaction and in tumour histopathology, especially as additional markers in the assessment of prognosis of melanoma patients. Changes in the expression of HLA antigens on tumour cells in vitro as induced by gamma-interferon may also occur in vivo as a result of local production by the T lymphocytic infiltrate in tumours.