Re-epithelialization of normal human excisional wounds is associated with a switch from αvβ5 to αvβ6 integrins

Summary During cutaneous wound repair, keratinocytes move laterally across the wound surface. For this lateral movement epidermal cells must disassemble their tenacious connections to the basement membrane and their neighbouring cells, and express surface receptors that permit translocation over the wound surface extracellular matrix. If the basement membrane is disrupted, the epidermis migrates over a provisional matrix that contains fibrinogen, fibronectin, vitronectin and tenascin. Although α5β1 integrin, a fibronectin receptor, is expressed by human epidermis during reepithelialization of excisional and incisional wounds, the spatial and temporal patterns of vitronectin, tenascin, and other fibronectin receptors are less clear. Other potential receptors include αvβ5 for vitronectin and αvβ6 for fibronectin and tenascin. To study provisional matrix integrin expression during human wound healing, full-thickness 4-mm punch biopsies were performed on the inner surface of the upper arm in adult volunteers. At 3, 7 and 14 days after injury wound sites were excised, bisected, quick frozen in liquid nitrogen, and examined for the expression of α5, β1, αv, β5 and β6. At 3 days, α5β1 and αvβ5, but not αvβ6, appeared around the basal and suprabasalar cells of the migrating epidermis. At 7 days, α5β1, αvβ5, and αvβ6 appeared around the perimeter of the basal cells of the migrating epidermis. By 14 days, when re-epithelialization was complete, all basal and suprabasalar cells overlying the wound expressed α5β1 and αvβ6, but not αvβ5. Thus, αv appeared to switch its heterodimeric association from β5 to β6 subunit during re-epithelialization.     

Lack of intrinsic polarity in the ligandbinding ability of keratinocyte β1 integrins

Abstract: Within the basal layer of the epidermis the β1 integrins have a pericellular distribution. Two monoclonal antibodies, 15/7 and 12G10, that detect a conformation of the β1 integrin subunit that is induced following cation or ligand occupancy selectively recognized β1 integrins at the basement membrane zone in vivo and in focal adhesions of cultured keratinocytes; they did not recognize integrins on the apical and upper lateral membranes of basal keratinocytes nor integrins on the suprabasal keratinocytes of hyperproliferative epidermis. Inhibition of intercellular adhesion did not induce the 15/7 epitope on the lateral and apical membrane domains. The surface distribution of the epitopes was consistent with the antibodies acting as reporters of ligand-binding; in addition, the 15/7 epitope was exposed on unglycosylated, immature β1 integrins. Although the apical membrane of basal keratinocytes is not normally in contact with extracellular matrix proteins, we found that it was capable of binding fibronectin-coated beads and that the 15/7 epitope was exposed on plasma membrane in contact with the beads. When a chimeric molecule consisting of the extracellular domain of CD8 and the cytoplasmic domain of the β1 integrin subunit, used to mimic a constitutively active β1 heterodimer, was introduced into keratinocytes it localized to the basal, lateral and apical membrane domains. We conclude that although the conformation of the keratinocyte β1 integrins differs between the basal and the lateral/apical membrane domains there is no intrinsic polarity in the ligand binding potential of the receptors.     

Expression of integrins in human nail matrix

Summary The aim of this study was to characterize cell-cell and cell-matrix interaction by evaluating the expression of different integrins in the nail matrix.
Nail biopsies were obtained from two cadaver lingers, and eight patients with ingrowing toenails. Frozen sections were stained by indirect immunofluorescence using anti-α, anti-α2, anti-α3 anti-α4, anti-α5, anti-α6, anti-αv, anti-β. anti-β4 and anti-ICAM-1 monoclonal antibodies. Biopsies from normal human foreskin were evaluated as controls, α. α4 and α5 subunits were absent from both nail matrix and normal human skin. α2, α3 and β1 subunits were expressed in the basal and suprabasal layers of nail matrix, but only in the basal layer of skin epidermis, α6 and β4 subunits were strongly expressed in the basement membrane zone and in the basal layer of both nail matrix and epidermis. The αv subunit was expressed in the basal layer of nail matrix. ICAM-1 was not expressed in nail matrix epidermis.
Our findings show that despite the distinctive features of the nail apparatus, compared with the epidermis, the pattern of integrin expression Is similar, although some differences in the distribution of α2. α3 and β1 subunits are detectable. These are probably related to the peculiar differentiation and keratinization of the nail.     

The role of the cutaneous cholinergic system in guttate psoriasis

In previous studies, high levels of acetylcholine (ACh) have been reported in psoriasis lesions. In addition, patients with guttate psoriasis respond to oral treatment with atropine. We wanted to know how the cutaneous cholinergic system could be involved in this process. Since mast cells (MC) are characteristic components of the inflammatory infiltrate of guttate psoriasis, we compared ACh receptor (AChR) composition and ACh production in both epidermis and mast cells of 10 patients with guttate psoriasis in involved and uninvolved skin on protein level using immunofluorescence and in a MC line (HMC-1) using PCR. We could confirm the presence of numerous MC in guttate psoriasis lesion. Both in vivo and in vitro , MC lacked expression of cholinacetyltransferase (ChAT), vesicular acetylcholintransorter (VAChT) and cholintransporter-1 (ChT-1) but contained high levels of acetylcholinesterase (AChE). In mast cells of both involved and uninvolved skin we found both nicotinic (α3, α5, α7, α9, α10, β2 and β4 subunits) and muscarinic (M1, M3, M4, M5) AChR. In HMC-1 cells all AChR subunits found in skin where present on mRNA level, except α7 and β2. In lesional epidermis both ACh production and AChR expression was shifted from the basal to the suprabasal layers especially the nicotinic α3, α5, α9, β2 and β4 and the muscarinic M3 and M5 AChR subunits. Our results exclude a role of the cholinergic system in the initiation of keratinocyte proliferation in the basal epidermal layer but point towards a role of epidermal AChR in suprabasal processes, most likely terminal differentiation and barrier formation as has been shown in other systems. Most importantly, mast cells are targets of paracrine and endocrine effects mediated by ACh and choline thus modulating inflammatory processes like guttate psoriasis and explaining the clinical efficacity of anticholinergic drugs like atropine.     

Analysis of cultured keratinocytes from a transgenic mouse model of psoriasis: effects of suprabasal integrin expression on keratinocyte adhesion, proliferation and terminal differentiation

Many important transgenic mouse models of benign and neoplastic skin diseases have been generated through the use of promoters that target transgene expression to the different epidermal layers. However, more mechanistic studies of the specific effects of the transgenes on keratinocytes have been hampered by difficulties in culturing keratinocytes from adult mouse epidermis and by the low differentiation potential of many established mouse keratinocyte lines. We have used the Rheinwald & Green technique to cultivate primary adult keratinocytes and to generate keratinocyte lines from transgenic mice which have a sporadic psoriatic phenotype due to expression of human integrin subunits under the control of the involucrin promoter. We show that the transgenes are induced when keratinocytes are placed in suspension and that the transgenic integrins are capable of clustering in focal adhesions and mediating cell adhesion and spreading. We also show that suprabasal integrin expression has no direct effect on proliferation of cells in the underlying basal layer, ruling this out as a possible explanation for the epidermal hyperproliferation observed in the transgenic mice.     

Antiepiligrin cicatricial pemphigoid represents an autoimmune response to subunits present in laminin 5 (α3β3γ2)

Sera from 20 patients with antiepiligrin cicatricial pemphigoid were studied to define the specific reactivity of their IgG autoantibodies. IgG from all patients bound exclusively to the dermal side of 1 mol/L NaCl split skin and immunoprecipitated laminin 5 (α3β3γ2) from extracts of human keratinocytes (HKs). Immunoblot studies on purified laminin 5 subunits demonstrated that patient IgG bound α3 alone in 16 patients. In two patients, IgG autoantibodies were directed predominantly to the γ2 subunit, yet showed trace reactivity to α3 as well. Sera from two patients did not immunoblot any laminin 5 subunits, their IgG presumably immunoprecipitating laminin 5 via a conformational epitope. Sera from patients with α3 subunit-specific IgG immunoprecipitated all subunits of laminin 5 as well as polypeptides of 190 and 200 kDa from the conditioned media of HKs. Preclearance studies and experiments utilizing affinity-purified patient IgG demonstrated that the latter signified laminin 6 (α3β1γ1) that was bound by cross-reactive α3 subunit-specific patient IgG. Sera from patients with γ2 subunit-specific IgG showed no reactivity to laminin 6, except for faint reactivity provided by low levels of their α3 subunit-specific IgG. Taken together, these findings indicate that antiepiligrin cicatricial pemphigoid signifies an autoimmune response to subunits present in laminin 5.     

VLA and α6β4 integrin expression in neuroendocrine carcinomas of the skin (their xenografts on nude mice and a corresponding primary culture)

Immunohistological expression of VLA1–5 and α6β4 integrins have been studied in 21 cases of primary neuroendocrine carcinomas of the skin (NECS), three xenografts on nude mice and one NECS cell culture. The phenotypic properties of NECS cells were largely maintained in NECS grafted on athymic nude-mice and in the corresponding cell line. Our results indicate that α1β1 and to a lesser extent α3β1,α5βl are the main integrins expressed in NECS. In addition, VLA2,4 and α6β4 are heteroge-neously expressed in the same group of tumors and very sparsely present. These data suggest that like neuroblastoma and primitive peripheral neuroectodermal tumor (pPNET) the absence or the heterogeneous distribution of such integrins is correlated with the aggressive behaviour of NECS although long-term follow-up was not available for our cases. On the other hand, the α1 expression could be regarded as a novel marker for differential diagnosis between NECS (α1+) and pPNET (α1−). The α1β1, α2β1, α3β1, α5βl heterodimers in the 21 NECS studied showed an uniform pericellular staining of both the peripheral cells and central cells of the tumor islands. The predominant expression of α1β1 is consistent with the hypothesis of a primitive epithelial totipotential origin in NECS.     

The distribution of α6β4 integrins in lesional and non-lesional skin in bullous pemphigoid

The alpha 6 beta 4 integrin is associated ultrastructurally with the hemidesmosomes of the basal keratinocytes and with the bullous pemphigoid antigen (BPA), suggesting an important role in adhesion of epidermal cells to the basement membrane. Using an immunofluorescence technique with chain-specific monoclonal antibodies to the alpha and beta subunits we have investigated the distribution of the alpha 6 beta 4 integrin in normal skin (n = 3) and in BP skin (uninvolved, perilesional and lesional) [n = 11]). The findings have been compared with other types of subepidermal blisters and with normal skin split by chemical means (n = 2) and by suction (n = 2). The distribution of alpha 6 beta 4 integrin was compared with that of bullous pemphigoid antigen (BPA) and with other basement membrane zone (BMZ) macromolecules, laminin, collagen type IV, collagen type VII and the BM600 antigen. In uninvolved, perilesional and early pre-blistered lesional BP skin the distribution of both the alpha 6 and beta 4 integrin subunits, BPA laminin, collagen types IV and VII and the BM600 antigen was identical to normal skin, i.e. a linear band in the BMZ. Within BP blisters, both alpha 6 and beta 4 integrin subunits and BPA were absent, except in two blisters in which the integrin expression was retained in the blister roof, despite loss of BPA. The other BMZ components were expressed on the blister floor.(ABSTRACT TRUNCATED AT 250 WORDS)     

Modulation of integrins and filaggrin expression by <Emphasis Type="Italic">Propionibacterium acnes</Emphasis> extracts on keratinocytes

Propionibacterium acnes plays an important role in the pathogenesis of acne and it is established that this bacteria is involved in the induction and maintenance of the inflammatory phase of acne. The aim of our work was to determine if P. acnes extracts could modulate integrins and filaggrin in vitro expression by keratinocytes. Integrins and filaggrin expression was examined using immunohistochemistry technique both on Normal Human Epiderminal Keratinocytes (NHEK) and on deep-frozen sections of normal human skin explants incubated with three different P. acnes extracts. In addition, the expression of filaggrin was investigated on biopsies of acne lesions and by western-blot associated with its precursor profilaggrin. We demonstrated that P. acnes extracts induced β1 integrin expression significantly on both proliferating keratinocytes and differentiated keratinocytes. In addition, P. acnes induced α3, α6s and αVβ6 integrin expression and filaggrin expression on differentiated keratinocytes. Finally P. acnes extracts increased filaggrin expression by suprabasal layer of epidermis of explants. Western-blot confirmed that total amount of filaggrin was increased. These results indicate that P. acnes extracts are directly able to modulate the differentiation of keratinocytes suggesting that this bacteria play a role not only in the development of inflammatory acne lesions but also in the formation of the microcomedo.     

The expression of integrin α2β1 and attachment to type I collagen of melanoma cells are preferentially induced by tumour promoter, TPA (12-O-tetradecanoyl phorbol-13-acetate)

Summary The adhesion of melanoma cells to the extracellular matrix (ECM) protein is likely to be essential in their invasive metastatic processes. Treatment with 12- O -tetradecanoyl phorbol-13-acetate (TPA), a potent protein kinase C (PKC) activator, preferentially induced the expression of α2β1 integrin, the receptor for collagen/laminin. The number of cells attached to type I collagen, but not laminin, was increased by treatment with TPA. Prior exposure to PKC inhibitors such as H-7 (20 μmol/1) and calphostin C (50μmol/1) had no effect on TPA-induced α2β1 integrin expression and cell attachment to type I collagen, whereas prior exposure to the calmodulin antagonist W-7(50 μmol/1) inhibited these TPA-induced events. The augmented adhesion was also inhibited by anti-α2 antibody. These data suggest that the increased attachment of melanoma cells to type I collagen appears to be mediated by the preferential augmentation of integrin α2β1, and the activation of calmodulin kinase, but not via the activation of PKC. Analysis of the expression of integrins and of cell attachment to ECMs is important in elucidating the mechanisms involved in the progression and metastasis of malignant melanoma.     

Altered expression of the α2 laminin chain in psoriatic skin: the effect of treatment with cyclosporin

The histopathological pattern of psoriasis is characterized by dermal inflammatory reaction and hyperproliferation of the epidermis. The mechanism of the epidermal hyperproliferation is not completely understood, but it is probably modulated by the basal lamina (BL), the alterations of which have not been described. We performed the present study to evaluate the expression of the α1, α2, β1 and γ1 laminin chains and collagen IV in the BL of active psoriasis vulgaris before and after cyclosporin treatment administered until the psoriasis was in remission. The results showed that the α2 chain is weak and irregular in the lesions, while the α1, β1 and γ1 chains and collagen IV are normal, with intense and continuous reaction. In the same subjects, this alteration was absent in skin that was clinically unaffected. After treatment with cyclosporin, the altered expression of the α2 chain returned to normal in the healing lesions.     

Effects of UVA on TNF-α, IL-1β, and IL-10 expression levels in human keratinocytes and intervention studies with an antioxidant and a JNK inhibitor

Objective: To understand the expressions and transduction pathways of cytokines in ultraviolet (UV)A-irradiated keratinocytes.
Methods: We cultured human keratinocytes of the HaCaT cell line and investigated both mRNA and protein expressions of cytokines in cells that were not irradiated or were exposed to 2.4 J/cm² UVA, with or without an antioxidant (β-carotene) or a c-Jun N-terminal kinase (JNK) inhibitor (SP600125).
Results: We demonstrated that the expression levels of tumor necrosis factor (TNF)-α and interleukin (IL)-1β were up-regulated in irradiated cells. IL-10 was not detected in non-irradiated cells, but was observed in irradiated cells. JNK was activated in irradiated cells and this could be antagonized by β-carotene. The UVA-induced up-regulation of these cytokines was also antagonized by β-carotene. SP600125 inhibited the UVA-induced increase in the expression of TNF-α mRNA and protein and in the expression of IL-1β mRNA.
Conclusions: The results suggest that oxidative stress may be an early intermediate effect in JNK-dependent UVA induction of cytokine expression in human keratinocytes in vitro .     

Molecular determination of laminin-5 degradation: a biomarker for mustard gas exposure diagnosis and its mechanism of action

Abstract:  Laminin-5, a heterotrimer of laminin α3, β3 and γ2 subunits, is a component of epithelial cell basement membranes. Laminin-5 functions as a ligand of the α3β1 and α6β4 integrins to regulate cell adhesion, migration and morphogenesis. In the skin, laminin-5 facilitates the assembly of basement membranes; thus it is essential for a stable attachment of the epidermis to the dermis and recovery of damaged skin. Sulphur mustard (SM), also known as mustard gas, is a vesicant that has been employed as a chemical weapon in various conflicts during the twentieth century. Skin exposure to SM results in fluid-filled blisters; proposed mechanisms are inflammation, protease stimulation, basal cell death and separation of the epidermis from the dermis apparently because of the degradation of attachment proteins like laminin-5. Therefore, we investigated the effects of SM exposure on the degradation of laminin-5 and its three subunits, α3, β3 and γ2 by exposing normal human epidermal keratinocytes (NHEK) to SM (0–300 μ m , 1–24 h). We found that SM degraded laminin-5 and its two subunits β3 and γ2, but not α3. Preincubation of cells with a serine protease inhibitor (PMSF), or a metalloprotease inhibitor (1,10-phenanthroline) prior to SM exposure partially prevented SM-induced degradation of laminin-5 subunits, β3 and γ2. Specificity studies showed that the degradation of laminin-5 γ2 was due to a bifunctional mustard compound such as SM, but not due to the other alkylating agents tested. Our results support that laminin-5 degradation is an important mechanism of SM injury as well as a useful biomarker of SM exposure. The knowledge of the mechanisms of laminin-5 degradation in SM-exposed NHEK has potential application in developing cutaneous therapeutics against SM.     

Expression of beta 4 integrins in human skin: comparison of epidermal distribution with beta 1-integrin epitopes, and modulation by calcium and vitamin D3 in cultured keratinocytes.

The expression of beta 4 integrins in adult and fetal human skin as well as in cultured keratinocytes was studied by immunodetection with monoclonal antibodies, and compared with that of beta 1 integrins. The distribution of the beta 1 and beta 4 integrin epitopes was entirely different in the adult epidermis. As reported previously by us (J Clin Invest 84:1916, 1989), the beta 1 epitopes were present most prominently at lateral cell-cell contact points, whereas staining with the beta 4 antibody demonstrated a linear staining pattern polarizing to the basal surface juxtaposed to the dermal-epidermal basement membrane. In contrast, in fetal skin, the staining patterns both with beta 1 and beta 4 antibodies were similar and demonstrated the presence of epitopes surrounding the entire cell surface of both basal and suprabasal keratinocytes. Distinct polarization of beta 4 integrin epitopes was noted in cultured keratinocytes maintained in low-calcium (0.15 mM) medium, and the expression of these integrins was also noted in human papilloma virus-transformed keratinocytes. Switch of the cultures to high-calcium (1.2 mM) medium resulted in redistribution of the epitopes to a pattern suggesting their location at under-surface of the cells adjacent to the substratum. This Ca(++)-induced redistribution of beta 4 integrin epitopes could be counteracted by 10(-7) M vitamin D3. Finally, incubation with anti-beta 4 integrin antibody reduced the capacity of keratinocytes to attach to plastic substratum. The results provide further evidence for the role of beta 4 integrins in cell-matrix interactions.     

Correlation between clonotypic T-cell receptor beta chain variable region (TCR-Vβ) gene expression and aberrant T-cell antigen expression in cutaneous T-cell lymphoma

Immunohistochemical studies can augment the clinicopathologic diagnosis of cutaneous T-cell lymphoma (CTCL). Our goal was to determine whether a panel of 11 T-cell receptor (TCR) beta chain variable region (V_β) monoclonal antibodies (moAbs) could consistently identify clonal T-cell populations within CTCL skin infiltrates, and whether these cells exhibited aberrant T-cell antigen expression. Biopsies from 24 CTCL and 3 parapsoriasis patients were analyzed. Of the 27 patients, 4 (15%) demonstrated T-cell clonality by restricted TCR-Vp moAb staining. The Vp+ restricted cells expressed aberrant antigen profiles. Overall, aberrant antigen profiles were detected in 18/24 (75%) CTCL patients. V_β18 moAb crossreacted with a 85 kD protein produced by basal and suprabasal keratinocytes. We conclude: 1) Restricted TCR-Vp expression correlated with aberrant T-cell antigen profiles; 2) In the absence of a complete panel of TCR-Vp moAbs, localization of aberrant T-cell antigen expression can be useful in identifying malignant T-cells within CTCL skin infiltrates; 3) The detection sensitivity and specificity of the currently available TCR-V_β moAbs may limit their utility to consistently detect clonal T-cell populations in CTCL skin biopsies; 4) A 85 kD protein present on basal and suprabasal keratinocytes is recognized by V_β18 moAb and may be related to immune function (s) of the epidermis.     

Altered expression of epithelial integrins and extracellular matrix receptors in oral erythema multiforme

Inflammation and ulceration at the epithelium-connective tissue interlace, a characteristic of erythema multiforme (EM), may be associated with altered molecular attachment of basal keratinocytes. To determine the expression of basal keratinocyte-associated integrins and their basement membrane ligands in oral EM, specimens of clinically and microscopically confirmed EM (n=12) and mucosal controls (n=7) were stained immunohistochemically for the integrins α3, β6, β1, and β4 and for extracellular matrix proteins laminin 1, laminin 5, collagen IV, and collagen VII using a standard avidin-biotin-peroxidase technique. In EM, results showed increased staining intensity for all integrins studied in basal and suprabasal keratinocytes. Basement membrane-associated staining of a6 and b4 was intense, but disrupted and fragmented. In EM, integrin staining was most marked at the summit of the connective tissue papillae. Laminin 5 staining was more intense than in controls, was frequently fragmented, and extended into the lamina propria. Laminin 1 staining was discontinuous and was frequently less intense than in controls. Collagen IV staining in EM was interrupted along the basement membrane. Collagen VII staining was fragmented but unchanged in intensity. These alterations in interface adhesion molecules suggest that hemidesmosome-associated molecules are important in the pathogenesis of EM. The staining intensities and patterns of expression of these adhesion molecules suggest that oral EM is initially focused in the connective tissue papillae.     

Adhesion molecule expression in normal skin and melanocytic lesions

Cell adhesion between surfaces of cells and to extracellular matrices represents a fundamental mechanism in tissue organization and influences the biological behaviour and the architecture of tumors. We investigated the expression of various adhesion molecules in normal skin (n=5), nevi (n=29), and malignant melanoma (n=10) by immunohistochemistry. Special attention was paid to the correlation between adhesion molecule expression and the respective architectural features, e.g. UV-induced morphological changes, and the arrangement of melanocytes in congenital nevi. In nevi, a single erythemagenic close of UV-light did not influence the influence expression of melanocytes, but results in an upregulation of α3β1- and α6β1-integrin within the suprabasal layers of the epidermis. This suprabasal labelling was associated with an increased number of suprabasal melanocytes in UV-irradiated nevi which were detected with HMB-45 antibody. Nine of 10 congenital nevi demonstrated a labelling of α4β1-integrin only in melanocytes of the deeper dermis. This integrin previously has been associated with high tumor thickness and the clinical outcome in melanomas. The integrin profile observed in melanomas differed in part from that seen in nevi with expression of β2-and β3-integrins in some cases. The results may indicate a correlation between adhesion molecule expression and histopathological findings in melanocytic lesions.     

Expression of tetra-spans transmembrane family (CD9, CD37, CD53, CD63, CD81 and CD82) in normal and neoplastic human keratinocytes: an association of CD9 with α3β1 integrin

Tetra-spans transmembrane family (TSTF) members (CD9, CD37, CD53, CD63, CD81 and CD82) have potent effects on cell growth, motility and adhesion in various cells. However, little is known about their expression in human skin. Using immunohistological techniques, we have studied the localization of all six members of TSTF in normal and carcinomatous human keratinocytes. CD9, CD81 and CD82 were expressed in the entire living layers of the epidermis. Their staining pattern was quite similar, and was mainly intercellular with occasional intracellular immunoreactivity. CD53 expression was confined to the intercellular spaces of the upper spinous or granular layer in the normal epidermis. No clear-cut expression of CD63 could be detected in the epidermis. CD37 was not detected at all. Cultured human keratinocytes also expressed CD9, CD81 and CD82 at the surface membrane of cell-cell boundaries. Expression of CD37 and CD53 was negative in cultured keratinocyte, while CD63 was clearly localized in the cytoplasmic lysosomes. An immunoprecipitation assay revealed that α3β1 integrin is molecularly associated with CD9. The expression of CD9, CD81 and CD82 was markedly down-regulated in basal cell carcinoma but not in Bowen's disease. The abundant and differential expression of TSTF molecules and the selective association of CD9 with α3β1 integrin suggest that the TSTF molecules may be involved in the regulation of epidermal differentiation and integrity in vivo.     

Tenascin is overexpressed in vitiligo lesional skin and inhibits melanocyte adhesion

The aetiology of vitiligo remains obscure. In this study, the role of integrins in the observed inability of melanocytes to repopulate lesional skin was investigated. Antibodies directed to α₂, α₃, α₅, α_v, α₆, β₁ and β₃ integrin subunits were used. Immunohistology revealed no marked differences in the overall levels of expression of integrins between control, non-lesional, perilesional or lesional skin. Moreover, no differences were noted in the level of expression of integrins or the adhesive capacity between cultured control cells derived from three separate donors and vitiligo-derived melanocytes from two donors. Rather, it was clearly observed that towards the lesion, vitiligo skin contains increasing amounts of tenascin in the basal membrane and papillary dermis in five patients employing T2H5 antihuman tenascin antibody. The anti-adhesive effect observed in vitro for this extracellular matrix molecule using normal melanocytes may contribute to loss of pigment cells in vitiligo or to ineffective repopulation of the lesions.     

The role of αEβ7 integrin (CD103) and E-cadherin in epidermotropism in cutaneous T-cell lymphoma

Adhesion molecules such as integrins and cadherins are thought to play a critical role in T-cell migration and localization within the epidermis (epidermotropism). The purpose of this study was to correlate T-cell expression of the integrin GD103 and E-cadherin in cutaneous T-cell lymphoma (CTCL). Serial sections of skin biopsies from 22 patients with CTCL and 13 with benign reactive dermatitis were stained with antibodies to CD4, CD103, and E-cadherin by the avidin-biotin peroxidase technique. CD 103 was expressed on single epidermotropic CD4+ T-cells in 9/9 early stage (patch/plaque) CTCL and 6/10 reactive dermatitis biopsies. Less than 30% of dermal T-cells expressed CD103. All 4/4 late stage (tumor) CTCL were GD103–. Epidermal aggregates of CD4+T-cells (Pautrier's microabscesses) were CD103–. E-cadherin was expressed on epidermal keratinocytes and follicular and sweat gland epithelia but not on T-cells.
We conclude that CD 103 expression on cutaneous T-cells parallels the degree of epidermotropism exhibited in both neoplastic and inflammatory disorders of the skin. E-cadherin is not expressed on T-cells infiltrating the skin. Further investigation is necessary to further elucidate the interaction between CD103 and E-cadherin in facilitating trafficking of T-cells into the epidermis.