T-cell receptor-gamma/delta bearing lymphocytes in normal and inflammatory human skin

Murine dendritic epidermal T cells (DETC) were recently reported to express T-cell receptor (TCR)-gamma/delta chains. In a search for the human equivalent of these cells, we tested normal and lesional skin with MoAb which react with the TCR-gamma/delta heterodimer. We performed indirect immunofluorescence (IF) on epidermal sheets, and alkaline-phosphatase-anti-alkaline-phosphatase complex (APAAP) on epidermal cell smears. Frozen skin sections from normal skin and various cutaneous lymphocyte infiltrates were also studied. A few CD3+ T lymphocytes were consistently found in normal epidermis. Most of these cells appeared to be TCR-alpha/beta +, and some CD4+ or CD8+. On epidermal sheets and cell smears, only a very small TCR-gamma/delta + cell population was visualized (less than 0.1% of the total). On normal skin sections, we observed 0 to 3 gamma/delta + cells per section. When present, they were often located in the epidermal basal layer, and were round or dendritic. Double immunolabeling revealed that gamma/delta + cells differed from CD1+ Langerhans cells, and that they had a similar phenotypic pattern as gamma/delta + peripheral lymphocytes (PBL): CD2+, CD3+, CD4-, and CD8-. Immunostaining from various inflammatory skin lesions showed that the dermal infiltrates included CD3+ T lymphocytes but virtually no gamma/delta + cells. Only a few gamma/delta + cells were found in some end-evolutive infiltrates. Taken together, these results strongly suggest that normal human epidermis occasionally harbors TCR-gamma/delta complex bearing lymphocytes, which constitute a small fraction of the CD3+ cutaneous T lymphocytes.(ABSTRACT TRUNCATED AT 250 WORDS)     

T-cell receptor gamma delta bearing cells in normal human skin.

T-cell antigen receptors (TCR) are divided into common alpha beta and less common gamma delta types. In the murine skin, TCR gamma delta+ cells have been reported to form the great majority of epidermal T lymphocytes. We have examined the relative contribution of TCR alpha beta+ and TCR gamma delta+ cells to the T-cell population in normal human skin. Serial sections of freshly frozen skin specimens were acetone fixed, incubated with anti-CD3, beta F1 (anti-TCR alpha beta), anti-TCR gamma delta-1 and anti-TCR delta 1 (anti-TCR gamma delta) monoclonal antibodies (MoAb), and stained with a highly sensitive method. Over 90% of the T cells of normal human skin are localized around the postcapillary venules of the dermis, while less than 5% are present within the epidermis. In papillary dermis, TCR gamma delta+ cells formed on average 7% (anti-TCR gamma delta-1) or 9% (anti-TCR delta 1) of the total number of CD3+ cells, while TCR alpha beta+ cells constituted up to 80%. In epidermis, these percentages were 18% and 29% for TCR gamma delta+ cells, and up to 60% for TCR alpha beta+ cells. It is concluded that there is no preferential immigration or in situ expansion of TCR gamma delta+ T cells in normal human skin, because the relative percentages found for the TCR alpha beta+ and TCR gamma delta+ populations in skin are comparable to those found in lymphoid organs and peripheral blood. However, the percentage of TCR gamma delta+ cells in epidermis seemed on average higher than in papillary dermis. Therefore, there may still be a difference in migration patterns of TCR gamma delta+ v TCR alpha beta+ cells, but this does not result in their preferential localization in human epidermis. The hypothesis that TCR gamma delta+ T cells have a specialized function in immunosurveillance of epithelia may thus not be valid for human epidermis.     

Expression of a cell adhesion protein (VLA β) in normal and diseased skin

Biopsies from normal skin (n = 17) and various cutaneous disorders (n = 83) were examined immunohistologically for reactivity with an antibody (CD29) against the common beta chain of the VLA integrin family. In normal skin, CD29 recognized a number of cell types, i.e. endothelial cells, fibroblasts, T lymphocytes and basal keratinocytes. Similar cells were positive in diseased skin, but the expression of VLA beta was upregulated on keratinocytes. The phenotype of the VLA beta-positive T cells was examined in more detail by staining with anti-T-cell antibodies, i.e. CD3, CD4, CD8, CD45RO (UCHL1) and CD45R (2H4). These studies showed that most of the T cells in normal skin, benign cutaneous conditions and early cutaneous T-cell lymphomas (CTCL) expressed a similar phenotype and resembled antigen committed 'memory' (helper/inducer) cells (CD4+, CD29+, CD45RO+, CD45R-). In advanced CTCL, expression of these antigens was more variable, and many of these infiltrates showed aberrant (or unusual) expression of CD29, CD45RO, CD45R and other T-cell antigens. It is concluded that several cells involved in cutaneous immune reactions express a molecule (VLA beta) which acts as a receptor for extracellular matrix components. This molecule is important for the attachment of cells to connective tissue constituents and may act to facilitate the migration of lymphocytes (and other cells) during immune reactions in normal and diseased cutaneous conditions. Advanced CTCL differ from the early lesions and it is possible that there is a progressive accumulation of increasingly malignant (or transformed) cells in these conditions.     

T lymphocytes bearing the γδ T-cell receptor: a study in normal human skin and pathological skin conditions

The aims of this study were to investigate the presence of gamma delta T cells in normal human skin, and the possible role of these cells in cutaneous reactions. Twenty-eight samples of normal skin from various sites, and 52 biopsies from inflammatory and neoplastic skin conditions were investigated by immunohistochemical techniques. In normal human skin gamma delta T cells were infrequently seen in the epidermis and dermis. In the inflammatory and neoplastic dermatoses, gamma delta T cells were occasionally present, accounting for 0-5% of CD3+ cells in most of the biopsies examined. In one case of pityriasis lichenoides chronica and one case of lichen planus gamma delta T cells were found to be increased, accounting for 15% of the CD3+ cells in each case. Dermal gamma delta T cells were markedly increased in three of six cases of Langerhans cell histiocytosis, with up to 30% of dermal CD3+ cells showing positive staining to an anti-T-cell receptor gamma delta monoclonal antibody. In two of these cases gamma delta T cells were seen in both the dermis and the epidermis. In two further cases dermal gamma delta T cells were not a prominent feature, but small clusters of epidermal gamma delta T cells were observed. T cells bearing the gamma delta T-cell receptor are thus not a major feature of normal human epidermis, unlike the murine system, where the great majority of epidermal lymphocytes express the gamma delta T-cell receptor.(ABSTRACT TRUNCATED AT 250 WORDS)     

CD4+ CD8+ (thymocyte-like) T lymphocytes present in blood and skin from patients with atopic dermatitis suggest immune dysregulation

BACKGROUND: Atopic dermatitis (AD) is a chronic inflammatory skin disease expressed early in life. Disease development is primarily determined by as yet unknown genetic factors, leading to the accumulation of activated T lymphocytes in the skin. OBJECTIVES: To investigate the nature of these T cells. METHODS: T-cell lines could be established from AD skin biopsies, but not from normal skin or AD peripheral blood, when placed in RPMI 1640 medium with 10% human AB serum, antibiotics, and the T-lymphocyte growth factors interleukins 2 and 4. The cell lines were subjected to phenotypic analysis using a fluorescence-activated cell sorter and compared with lymphocytes from AD and normal control peripheral blood. RESULTS: T-cell lines from 22 of 24 consecutive skin biopsies taken from 24 adult patients with AD were established. All cells were T lymphocytes expressing several activation markers. A significant proportion of the lymphocytes had stable expression of a CD4+ CD8+ phenotype (26% +/- 6%; mean +/- SEM). Such double-positive T lymphocytes are normally only seen in the thymus and not in the peripheral immune system. CD4+ CD8+ cells in peripheral blood of the patients (12.5% +/- 3.3%) were also detected. CONCLUSIONS: We suggest that a basic pathophysiological change in AD may be a faulty maturation of the T-lymphocyte system, leading to skin inflammation with CD4+ CD8+ T lymphocytes resembling immature T cells. This is likely to lead to skewing of many immune reactions in the patients.     

Is epidermal cell proliferation in psoriatic skin grafts on nude mice driven by T-cell derived cytokines?

Plasminogen activity and DNA synthesis by epidermal cells have been reported to be doubled in psoriatic skin grafts compared with grafts of normal skin 6 weeks after transplantation to nude mice. In our study human lymphocytes disappeared from such grafts within 48 h whilst some DR-positive human dendritic cells were retained in the grafts for up to 4 weeks. However, the grafts were infiltrated by Thy 1.2+ mouse lymphocytes within 6 days and this infiltration persisted at a moderate level throughout the observation period. It consisted of perivascular aggregates, scattered dermal and papillary T cells, and some mouse T cells were also found in the epidermal compartment. Grafts of psoriatic and non-psoriatic control skin were infiltrated to a similar extent, suggesting a low-grade rejection response against the human xenografts. These findings raise the possibility that psoriatic keratinocytes are responding abnormally to inflammatory cytokines released by mouse lymphocytes reacting against the skin grafts.     

Phenotypic heterogeneity of lymphoma of the skin

We studied surface markers present in 56 cases of lymphoma of the skin by immunohistochemical staining, using the ABC (avidin-biotin-peroxidase complex) and PAP (peroxidase-antiperoxidase complex) methods. Of these cases, 49 were T-cell lymphoma and 7 were B-cell lymphoma. Ten of the 49 cases of T-cell lymphoma were adult T-cell leukemia/lymphoma (ATL). Twenty-five of 31 cases of T-cell lymphoma except ATL analyzed by the ABC method showed a helper/inducer phenotype (Leu2a-,Leu3a+), two cases showed a suppressor/cytotoxic phenotype (Leu2a+, Leu3a-), one case showed Leu2a+Leu3a+, one case showed an inducer phenotype (Leu2a-, Leu3a+, Leu9+), and one case showed OKT11+, Leu2a-, Leu3a-, Leu1-, Leu9+, CD25+, Leu10+, CD30+. One CD8+ lymphoma was Pagetoid reticulosis, and a CD4+, CD8+ lymphoma was lymphomatoid papulosis with erythematous plaque. Cutaneous T-cell lymphoma (CTCL), previously described by Edelson et al., is defined as a helper T-cell lymphoma with marked affinity for the skin. In our study, 5 cases of T-cell lymphoma of the skin were not CTCL as described by Edelson et al. These results show that T-cell lymphoma of the skin is heterogeneous in nature. In other words, CTCL is one type but represents a major proportion of T-cell lymphomas of the skin.     

Local involvement of antigen-presenting cells and activated T cells in perilesional and clinically uninvolved skin in pemphigus vulgaris

Biopsies obtained from both the perilesional areas and clinically uninvolved skin of patients with pemphigus vulgaris (PV) were studied for antigen-presenting cell and lymphocyte phenotype and/or activation phenotype using monoclonal antibodies in avidin-biotin-peroxidase complex staining. Perilesional PV skin contained CD4+ and CD8+ T lymphocytes as the predominant cell type, but cells with a potential antigen-presenting function displaying CD11b phenotype of monocyte/macrophages and, in particular, CD1 phenotype of Langerhans cells were also present. The number of mononuclear inflammatory cells was greater in perilesional than in clinically uninvolved PV skin, and so were the proportions of CD4+, CD8+, CD25+, Ia+ cells (p less than 0.01), and CD1+ Langerhans cells and transferrin receptor positive cells (p less than 0.05). These findings confirm and extend earlier observations on local involvement of immunocompetent cells in PV.     

CD4+ cutaneous T-cell lymphomas show the phenotype of helper/inducer T cells (CD45RA-, CDw29+)

CD4+ T cells are heterogenous and include at least two subsets that differ in their influence to immunoglobin synthesis, cytokine secretion pattern and immunophenotype. Among others these subsets have been designated as suppressor/inducer or naive T cells (CD45RA+, CDw29-) and helper/inducer or memory T cells (CD45RA-, CDw29+). Current theories suggest that these CD4+ T-cell subsets either reflect sequential stages of maturation before and after activation (antigen contact) or represent distinct lineages. In this study, we systematically analyzed the participation of both suppressor/inducer (CD45RA+) and helper/inducer (CDw29+) T cells in the dermal lymphohistiocytic infiltrate of various CD4+ cutaneous T-cell lymphomas. Although in peripheral blood both subsets are equally distributed, we present evidence that all CD4+ cutaneous T-cell lymphomas are of the helper/inducer T cell phenotype. These findings are of importance both for pathogenetic and clinical considerations: the presence of plasma cells in dermal infiltrates and the elevation of serum immunoglobulins in patients of mycosis fungoides may be the consequence of interleukin-4 secretion of the neoplastic CD4+ helper/inducer cells. The exclusive memory T cell phenotype of cutaneous T-cell lymphomas may be due to a general predominance of this subset in the skin, or be the consequence of cellular activation during malignant transformation.     

Identification of lesional CD4+ CD25+ Foxp3+ regulatory T cells in Psoriasis

BACKGROUND: Depletion of CD4+ CD25+ Foxp3+ naturally occurring regulatory T cells (T(reg)) induces autoimmune phenomena. These cells have not yet been fully characterized in the skin of psoriatic patients. OBJECTIVES: To prove that the Zenon immunofluorescent labeling technique is suitable for the demonstration of co-localization of T-cell markers and in particular to show the distribution of T(reg) in psoriatic skin. METHODS: In biopsies derived from normal and psoriatic skin, CD4+ CD25+, CD4+ CD45RO+, CD8+ CD25+, CD8+ CD45RO+ and CD4+ CD25+ Foxp3+ cells in the dermis and in the epidermis were immunophenotyped, using a quantitative immunofluorescent labeling technique (Zenon), analyzed and compared using image analysis. RESULTS: The immunofluorescent labeling technique was shown to be an easy and reliable tool to demonstrate co-localization of T-cell markers. In psoriasis, all pathogenic T-cell subsets (CD4+ CD25+, CD4+ CD45RO+, CD8+ CD25+ and CD8+ CD45RO+ cells) were significantly increased in the dermis and in the epidermis, as compared to normal skin (all p < 0.05). Using this labeling technique we were able to reveal CD4+ CD25+ Foxp3+ T(reg) in psoriatic dermis, but not in the dermis of normal skin (p < 0.0001). CONCLUSIONS: The Zenon immunofluorescence technique in combination with image analysis is suitable for the demonstration of co-localization of T-cell markers in tissue. Increased numbers of pathogenic T cells (CD4+ CD25+, CD4+ CD45RO+, CD8+ CD25+ and CD8+ CD45RO+) were shown in the dermis and epidermis, whereas CD4+ CD25+ Foxp3+ T(reg) were identified in psoriatic skin with a predilection for the upper dermis.     

Cutaneous T-cell lymphoma lesional epidermal cells activate autologous CD4+ T lymphocytes: involvement of both CD1+OKM5+ and CD1+OKM5- antigen-presenting cells

Cutaneous T-cell lymphoma is characterized by infiltration of the skin by activated CD4+ T lymphocytes. The mechanism by which these T lymphocytes achieve and maintain their activated state is unknown. Antigen-specific activation of T lymphocytes is dependent upon antigen-presenting cells which express HLA-DR class II major histocompatibility complex molecules, such as epidermal Langerhans cells. In addition to CD1+DR+ Langerhans cells, cutaneous T-cell lymphoma lesional epidermis contains major histocompatibility complex class II positive non-Langerhans cell populations, including CD1+OKM5+ bone-marrow-derived cells and DR+ keratinocytes. We asked whether any of these epidermal cell populations demonstrate capacity to activate T lymphocytes. Various numbers of epidermal cells from uninvolved and involved cutaneous T-cell lymphoma plaques were therefore used to stimulate autologous CD4+ and CD8+ T lymphocytes in the absence of exogenous antigen. Involved epidermal cells potently induced proliferation of CD4+ T lymphocytes (S.I. +/- SEM = 466 +/- 45). In contrast, uninvolved epidermal cells only induced background levels of proliferation (S.I. +/- SEM = 2 +/- 0.5, N = 8, p less than 0.01). Neither involved nor uninvolved epidermal cells were able directly to activate CD8+ lymphocytes. The capability of involved epidermal cells to activate CD4+ T lymphocytes was dependent upon CD1+DR+ leukocytes and not DR+ keratinocytes, because depletion of either HLA-DR+, CD1+ or HLe1+ epidermal cells totally abrogated the T-lymphocyte proliferation. Interestingly, on a cell per cell basis CD1+DR+ cells obtained from involved skin, demonstrated relative to CD1+DR+ cells from uninvolved skin, enhanced capacity to activate CD4+ T lymphocytes. Furthermore, CD1+OKM5+ cells from involved epidermis stimulated autologous CD4+ T lymphocytes. This indicates that a unique hitherto undescribed CD1+OKM5+ epidermal antigen-presenting cell population may participate in T-lymphocyte activation. These findings provide support for the concept that the epidermal cells in cutaneous T-cell lymphoma patients, particularly the antigen-presenting cells, may contribute significantly to the activation of CD4+ malignant and/or non-malignant inflammatory T lymphocytes within the skin.     

Characterization of factor XIIIa positive dermal dendritic cells in normal and inflamed skin

The immunocytochemical identification and characterization of indigenous dermal dendritic cells (dermal dendrocytes) using a rabbit polyclonal antibody to clotting enzyme factor XIII subunit A (FXIIIa) was carried out on normal and inflamed human cutaneous tissue. The immunophenotype of FXIIIa positive dendritic cells was analysed with a panel of 18 monoclonal antibodies using immunoperoxidase and double immunofluorescence staining techniques. The antibody against FXIIIa detected highly dendritic dermal cells located particularly in the upper reticular and papillary dermis. Double fluorescence microscopy showed that FXIIIa positive cells were bone marrow derived (HLe-I+) and co-expressed monocyte, macrophage or antigen presenting cell markers (HLA-DR+, LFA-I+, HLA-DQ+, OKM5+, Mo I+, Mono-I+, Leu M3+). No labelling was obtained with cell markers for Langerhans cells (CDI), T lymphocytes (CD2), granulocytes (LeuMI) fibroblasts (Te7), intercellular adhesion molecule-I (ICAM-I) or endothelial cells (Factor VIII related antigen). Gamma interferon induced increased expression of HLA-DR and co-expression of ICAM-I on FXIIIa+ dermal dendritic cells in normal skin in organ culture. Moreover, in benign inflammatory dermatoses such as atopic eczema and psoriasis there was an increased number of FXIIIa+, DR+, ICAM-I+ cells in the upper dermis and foci of FXIIIa+ cells in the epidermis closely associated with lymphocytes. FXIIIa positive cells in human skin represent a specific population of bone-marrow dermal dendritic cells, distinct from Langerhans cells, that share some features common to mononuclear phagocytes (monocyte/macrophages). In addition, the detection of HLA-DQ on 48% of FXIIIa+ cells and the lack of OKMI in combination with high OKM5 expression suggests an antigen-presenting cell phenotype.     

Predominance of “memory” T cells (CD4+, CDw29+) over “naive” T cells (CD4+, CD45R+) in both normal and diseased human skin

Summary Absolute numbers of CD3+ T lymphocytes and their subpopulations were determined and statistically evaluated in the lesional skin of psoriasis, atopic dermatitis, nummular dermatitis, pityriasis rosea, and lichen planus. Skin sections were divided into horizontal layers and the numbers of CD3+ T cells as well as CD4+ inducer and CD8+ suppressor-cytotoxic T-cell subsets were counted. In addition, absolute numbers of the two subpopulations of inducer T cells, i.e., memory (4B4+ 2H4-) and naive (4B4- 2H4+) were evaluated. Unexpectedly, epidermal infiltration by T cells was highest in psoriasis and lowest in atopic dermatitis. In most cases, this exocytosis was dominated by CD8+ suppressor/cytotoxic T lymphocytes, with a minimal epidermal mean CD4/mean CD8 ratio of 0.04 in pityriasis rosea and a maximum of 0.48 in psoriasis. Inducer T cells within the epidermis were almost exclusively of the 4B4+ 2H4- memory T-cell subpopulation, whereas 4B4- 2H4+ naive T cells were extremely uncommon in lesional epidermis. Similar results were obtained for dermal T cells in all diseases studied, i.e., 4B4- 2H4+ naive T cells were relatively rare. Papillary dermis infiltration by T cells was highest in lichen planus where a mean CD4/mean CD8 ratio of 1.10, the minimum in this comparative study, was obtained. The mean CD4/mean CD8 ratio of the papillary infiltrate was highest in atopic dermatitis (4.12). Our results indicate disease-specific and significantly different infiltration patterns of T-lymphocyte subsets in the chronic inflammatory dermatoses investigated. The predominant presence of the CD4+ 2H4- memory subpopulation of CD4+ T cells in all diseases studied as well as in normal human skin (reported previously) seems to indicate that the skin immune system is rather unidirectional in its increase in this subpopulation of the inducer T-cell subset. This predominance of the memory subpopulation thus indicates that most T cells of normal and diseased human skin are already primed, i.e., have already met their specific ligand in a MHC II context.     

The HECA-452 epitope is highly expressed on lymph cells derived from human skin

The cutaneous lymphocyte-associated antigen (CLA), recognized by the monoclonal antibody HECA-452, is a cell surface glycoprotein that binds specifically to E-selectin. CLA is present on most T cells at sites of cutaneous immune response and has been shown to be important in lymphocyte homing to the skin. It is expressed only by a minor subset of peripheral T cells and is absent on thymocytes. We have analysed (using a FACScan flow cytometer) the expression of CLA on human lymph cells derived from normal skin, from ultraviolet (UV)-irradiated skin and from allergic contact dermatitis. Whereas in the peripheral blood CLA was expressed on < 20% of CD4 +, CD8 + and CD56 + cells (natural killer cells), > 60% of CD4 +, CD8 + and CD56 + cells isolated from skin-derived lymph expressed CLA. Furthermore, > 90% of CD1a + dendritic lymph cells were positive for CLA. UV irradiation of the skin and induction of an allergic contact dermatitis did not change CLA expression on lymph cells, although lymph flow and cell output increased. These results provide further evidence for an important role of CLA in cell homing to the skin.     

Role of integrin alphaE(CD103)beta7 for tissue-specific epidermal localization of CD8+ T lymphocytes

Tissue-specific T cell localization is crucial for immune surveillance of normal tissues and the pathogenesis of inflammatory disorders. In psoriatic skin, CD8+ lymphocytes predominantly reside within the epidermis, whereas CD4+ T cells are most abundant within the dermis. Molecular mechanisms guiding this spatial compartmentalization are not completely understood, however. Here, we demonstrate that 55% (+/-9.7%, n = 14) of the epidermal T cells, predominantly of the CD8+ phenotype, expressed the integrin alphaE(CD103)beta7. In contrast, only 5% (+/-2.0%) of the dermal T cells were alphaE(CD103)beta7+. Integrin alphaE(CD103)beta7 was not detected in normal skin (n = 10), and less than 1% of peripheral blood lymphocytes derived from normal (n = 11) or psoriatic (n = 10) donors expressed alphaE(CD103). When cultured T lymphoblasts (n = 12 donors) were stimulated with transforming growth factor beta1, expression of integrin alphaE(CD103)beta7 was induced on 52.8% (+/-16.2%) of CD8+ cells, but only on 6.1% (+/-2.3%) of CD4+ cells, suggesting selective inducibility on CD8+ lymphocytes. Whereas similar overall expression of transforming-growth-factor-beta1-specific mRNA was detected in normal and psoriatic skin by real-time quantitative polymerase chain reaction, immunohistochemistry revealed focal overexpression of transforming growth factor beta1 underneath psoriatic, but not normal, epidermis. This heterogenous transforming growth factor beta1 expression may contribute to induction of alphaE(CD103) in vivo. Adhesion of transforming-growth-factor-beta1-stimulated CD8+, but not CD4+, T cells to cultured keratinocytes and psoriatic epidermis in frozen sections could be significantly inhibited by antibodies that blocked the alphaE(CD103)/E-cadherin interaction. Co-culture of lymphoblasts and keratinocytes resulted in marginal enhancement of alphaE(CD103)beta7 expression in some cases. Overall, integrin alphaE(CD103)beta7 appears to contribute to tissue-specific epidermal localization of CD8+ T lymphocytes.     

Expression of 1,25-dihydroxyvitamin D3 receptors in normal and psoriatic skin.

Increasing evidence suggests an immunoregulatory function of the potent steroid hormone 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) which has been successfully applied for treatment of psoriasis. The skin is both a site of production and a target of 1,25(OH)2D3. In vitro, 1,25(OH)2D3 inhibits proliferation and stimulates differentiation of keratinocytes. We investigated the in situ expression of vitamin D-receptors (VDR) in normal and psoriatic skin by immunochemical methods. The VDR were visualized using the monoclonal antibody (MoAb) 9A7g to the VDR and the labeled avidinbiotin technique. Immunoreactivity was consistently confined to nuclei in all skin biopsies. In normal skin specimens (n = 10) VDR antigens were expressed in keratinocytes of all epidermal layers (except those of the stratum corneum) and in cells of the epidermal appendages. Double labeling experiments with MoAb to cluster-defined antigens indicated that melanocytes and approximately 75% of Langerhans cells exhibit 1,25(OH)2D3 receptors in normal skin biopsies (n = 5). Depending on their localization in skin compartments 42-62% of CD11b+ positive macrophages and 45-75% of CD3+ T lymphocytes expressed VDR. Non-lesional psoriatic skin specimens (n = 8) revealed nearly identical staining patterns. Lesional psoriatic skin specimens (n = 8) exhibited a significant increase of VDR expression both in basal and suprabasal epidermal layers as measured by computer-assisted morphometry and showed a remarkable change of the immune cell pattern: the densitity and proportion of VDR positive T lymphocytes and macrophages were higher in the epidermal and the perivascular papillary loop compartment. These in vivo findings strongly support the hypothesis that 1,25(OH)2D3 modulates immune response and cell proliferation/differentiation in human skin.     

Expression of the T-cell activation antigens CD27 and CD28 in normal and psoriatic skin

Activated T lymphocytes are thought to be involved in the pathogenesis of psoriasis. From studies with peripheral blood T lymphocytes it is known that T cells show a decrease in membrane expression of CD27 molecules during continuous antigenic stimulation. The T-cell activation molecule CD28 is thought to be involved in the transduction of an antigen-non-specific costimulatory signal. Therefore, in order to elucidate further the pathogenesis of psoriasis we studied the expression of CD27 and CD28, together with CD4, CD8 and CD45RA in this benign inflammatory dermatological disease. We used immunohistochemical techniques to determine absolute numbers of T lymphocytes and expression of these T-cell activation and T-subset-specific molecules in normal (n= 7), uninvolved perilesional (n= 7) and lesional psoriatic (n= 7) skin. We found that not only lesional but also clinically uninvolved perilesional skin showed an increased number of T cells. Further, immunohistochemical studies showed that CD27 is expressed by a minority of normal skin T cells, while in lesional psoriatic skin, expression was even lower, and almost absent in perilesional skin sections. In contrast to normal skin, both perilesional and lesional psoriatic skin contained no CD28 positive T cells. In lesional psoriatic skin, however, T cells showed predominantly the CD4 phenotype, while in perilesional skin CDS positive T cells were dominant. Two conclusions were reached: first, the absolute number of T cells, their CD27, CD28 and CD45RA expression, and the influx of CD8 positive T cells, indicate that perilesional psoriatic skin is different from normal and lesional psoriatic skin; and secondly, the data on CD27 and CD28 suggest that not only lesional but also perilesional psoriatic skin is subject to continuous antigenic stimulation, thus leading to decreased CD27 and CD28 expression on skin T cells.     

An immunohistochemical study of CD4, CD8, TIA-1 and CD56 subsets in inflammatory skin disease

BACKGROUND: Antibodies to CD4, CD8, TIA-1, and CD56 are available which perform well in formalin-fixed and paraffin-embedded tissue. While previous studies have investigated CD4 and CD8 subsets in inflammatory skin disease, few have specifically addressed TIA-1 and CD56 reactivity in benign dermatoses. Given that CD8, TIA-1, and CD56 are linked to aggressive lymphoproliferative disorders (i.e. subcutaneous panniculitic T-cell lymphoma, natural killer (NK), and NK/T-cell lymphomas), it would be important to determine their specificity for cutaneous hematologic malignancies. This investigation was undertaken to determine the frequency with which common, benign dermatoses express these four markers. We also sought to determine whether the ratio of CD4- to CD8-positive cells could be used to distinguish among the dermatoses, especially the superficial and deep perivascular ones. METHODS: Formalin-fixed and paraffin-embedded sections from a variety of common inflammatory dermatoses were stained with antibodies to CD4, CD8, TIA-1, and CD56. Positive reactions were scored as a percentage of the entire mononuclear cell infiltrate. RESULTS: All of the dermatoses represented in the study showed TIA-1- and CD56-positive lymphocyte subpopulations. On a case-by-case basis, the percentage of positive cells varied, and while all cases were positive for TIA-1, many were completely negative for CD56. For TIA-1, the percentage of positive cells ranged from 21 to 59%, and for CD56, from < 1 to 9%. The CD4:CD8 ratio ranged from 1.0 to 6.0 but was never less than 1.0. In addition to lymphocytes, TIA-1 also stained polymorphonuclear leukocytes, eosinophils, and mast cells. CONCLUSION: TIA-1- and CD56-positive lymphocytes are common participants in routine inflammatory dermatoses, and therefore these markers are not specific for aggressive lymphoproliferative disorders. Using only immunohistochemical data, the ratio of CD4- to CD8-positive lymphocytes could not be used reliably to separate the superficial and deep perivascular dermatoses from one another. Finally, mast cells are positive for TIA-1 and are commonly seen in normal and inflamed skin, and thus TIA-1 is not specific for cytotoxic T lymphocytes.