Preferential binding of monocytes and Leu 2+ T lymphocytes to interferon-gamma treated cultured skin endothelial cells and keratinocytes

The Measurement of Serum Tumor Necrosis Factor-alpha Levels in Patients with Lichen Planus

Background:

Lichen planus is a common mucocutaneous inflammatory skin disease with a multifactorial etiology. Cytokines have a key role in its pathogenesis. In our study, we aimed to investigate the relationship between the disease severity and levels of the tumor necrosis factor alpha (TNF-α) cytokine which was considered as a primary cytokine that initiates the cytotoxicity.

Materials and Methods:

A total of 34 patients with lichen planus who were 18 year or older and gender-matched healthy controls were included in the study. Serum TNF-α levels were measured by human TNF-α enzyme-linked immunosorbent assay test kits and the values in the two groups were statistically compared.

Results:

The mean serum TNF-α levels were higher in the patient group than that in the control group. Serum TNF-α levels were not associated with oral mucosal involvement and gender. However, it was observed that the level of TNF-α was higher in older ages, both in patient and in control groups.

Conclusion:

It is thought that TNF-α, a proinflammatory cytokine, may have an important role in the pathogenesis of lichen planus.

The measurement of serum TNF-α levels in patients with lichen planus

BACKGROUND

Lichen planus is a common mucocutaneous inflammatory skin disease with a multifactorial etiology. Cytokines play a key role in lichen planus pathogenesis. This study investigates the relationship between disease severity and levels of tumor necrosis factor-α (TNF-α), which is considered a primary cytokine that initiates cytotoxicity.

MATERIAL AND METHODS

Serum TNF-α levels were compared between a patient group (n = 34) and a control group (n = 20). TNF-α serum levels were measured using human TNF-α Enzyme-Linked Immunosorbent Assay (ELISA) test kits, and the two groups were statistically compared to each other.

RESULTS

Mean serum TNF-α levels were found to be significantly higher in the patient group than in the control group (p < 0.005). However, no significant association was observed between TNF-α levels and oral mucosal involvement (p > 0.005). No relationship was detected between TNF-α levels and patients' sex.

CONCLUSION

It is thought that TNF-α, a proinflammatory cytokine, may play an important role in the pathogenesis of lichen planus. TNF-α may be a simple and effective predictor to illustrate the inflammatory status in patients with lichen planus.

Interferon-gamma preferentially reduces memory/effector CD8 T lymphocytes in healthy subjects

To evaluate the influence of interferon-gamma (IFN-gamma) on leukocyte dynamics, with a focus on naive and memory T cells, we studied 6 healthy subjects twice in a placebo-controlled trial: once after the administration of recombinant human IFN-gamma (rhIFN-gamma; 100 microg/m2 subcutaneously) and at least 4 weeks later, after the administration of saline solution. Additionally, we studied the expression of adhesion molecules on T lymphocytes after in vitro incubation of whole blood with rhIFN-gamma. IFN-gamma induced a significant depletion in the number of T lymphocytes (P < .05 vs control), which was more severe in the CD8+ cell subset than in the CD4+ T cell subset. The numbers of naive CD4+ T cells and memory CD4+ T cells were equally affected by IFN-gamma, whereas within the CD8+ T cell subset, memory/effector cells disappeared preferentially as compared with naive cells (P < .05 vs control). In addition, IFN-gamma induced a decrease in B cells, NK cells, and monocytes. After an initial increase, granulocyte counts decreased significantly as compared with controls. These effects appeared not to be caused by the minimal rise in plasma cortisol levels (P < .05 vs control). In vitro, IFN-gamma did not up-regulate the expression of CD11a, NKI L16, CD11b, LFA-3, or VLA-4. We conclude that the administration of a single dose of IFN-gamma to healthy subjects profoundly affects the numbers of several leukocyte subsets in the peripheral blood compartment.

Immunopathogenesis of oral lichen planus and recurrent aphthous stomatitis

Oral mucosal bullous/desquamative/ulcerative diseases involve immunopathological mechanisms that account for loss of adhesion between contiguous keratinocytes or to structures within the basal lamina. Some are antibody mediated, in which specific adhesion molecules of the desmosome, hemidesmosome, and basement membrane become antigenic targets. Oral lichen planus and recurrent apthous ulcers, although manifesting disparate clinical appearances and natural history, share immunopathological features that involve T cell-mediated immunity. Although the antigens, haptens, or autoantigens are not usually apparent, current research poses the hypothesis that both of these common oral mucosal diseases are a delayed-type hypersensitivity or cell-mediated response to an antigenic stimulus residing within the epithelium. This article reviews the research evidence for this hypothesis.

Cutaneous eruption of lymphocyte recovery mimicking mycosis fungoides in a patient with acute myelocytic leukemia

Eruption of lymphocyte recovery (ELR) develops in the setting of leukocyte reconstitution after iatrogenic marrow aplasia and displays a superficial perivascular lymphocytic infiltrate composed of CD3+/CD4+ cells. Epidermal changes are usually minimal to absent. We report a case of an ELR mimicking mycosis fungoides with the formation of CD4+ Pautrier-like microabscesses.

The development of manifest psoriatic lesions is linked with the appearance of ICAM-1 positivity on keratinocytes

The development of psoriatic lesions was studied in 36 psoriatic patients using the Koebner reaction induced by tape stripping. Two biopsies per patient were taken from non-lesional psoriatic skin before, and 6 h, 2 days, 7 days, 14 days and 21 days after tape stripping. Alterations in HLA-DR, ICAM-1, Ki-67 and FXIIIa positivities in both the dermis and the epidermis were estimated using immunohistochemical methods. A double staining for CD4+ and CD8+ T cells was also carried out to show their possible Ki-67 positivity. Results were compared with those from lesional (mature plaque) and non-lesional psoriatic skin, and control skin. Of the 36 patients, 9 were Koebner-positive. The most important finding in Koebner-positive psoriatic skin was the appearance of ICAM-1 positivity on epidermal keratinocytes simultaneously with the clinically observed lesion on day 7. The number of FXIIIa+ dendrocytes in the dermis was quite constant, and increased in mature psoriatic lesions only. The number of active HLA-DR+ immunocompetent cells increased in developing psoriatic lesions, being highest in mature lesions, but no Ki-67 positivity was detected in epidermal or dermal T cells in the psoriatic specimens. Based on these results, it is concluded that T cells divide and are activated extracutaneously in psoriasis, and also that ICAM-1/LFA-1 interactions are important in the recruitment of inflammatory cells and in controlling the effector cell functions.

Immunopathology of oral mucosal ulcerative, desquamative, and bullous diseases. Selective review of the literature

Cell/cell and cell/matrix adhesion proteins are responsible for maintaining the integrity of the mucosal lining of the oral cavity. Disease processes that destroy keratinocytes or adversely affect their adhesion to one another or to the subjacent basement membrane will result in erosions, ulcerations, and desquamations. Immunologic processes that have a deleterious effect on the integrity of the epithelial/basement membrane/submucosa complex are reviewed, and current research findings with respect to pathogenesis are discussed. In particular, T-cell-mediated hypersensitivity is involved in recurrent aphthous stomatitis and lichen planus; humoral-mediated immunity to cadherin intercellular adhesion molecules is important in the process of acantholysis in pemphigus vulgaris, and genetic defects and antibody-mediated processes give rise to junctional separation in epidermolysis bullosa and mucous membrane pemphigoid, respectively. An immune complex mechanism appears to underlie the pathogenesis of erythema multiforme.

Specific lymphocytotoxic destruction of autologous epithelial cell targets in recurrent aphthous stomatitis

Concepts of the immunopathogenesis of recurrent aphthous stomatitis (RAS) based on lesion histology suggest an early role for CD4+ T cells. Other in vitro studies show enhanced destruction of epithelial targets by peripheral blood mononuclear cells (PBMC) from RAS subjects. The present project aimed to extend these studies under conditions simulating the in vivo situation. Epithelial cells were cultured and induced to express class I and class II major histocompatibility complex (MHC) antigens with gamma interferon (gamma-IFN). Co-cultures with autologous PBMC showed evidence of specific destruction of epithelial targets in RAS patients when compared with a control group. Co-culture with CD4+ enriched cells also showed specific epithelial cell lysis. Effector cells pre-incubated with interleukin-2 (IL-2) did not produce increased destruction of epithelial cells. This study has supported previous work and identified an early role of CD4+ cells.

Haemorrhagic cellulitis: a syndrome associated with tumour necrosis factor-alpha

A newly defined clinical syndrome, haemorrhagic cellulitis, is described in 12 patients. The syndrome consists of an acute onset of extremely painful erythema affecting dependent areas, followed by dermal haemorrhage and sloughing of the overlying epidermis, and requiring both antibiotics and systemic corticosteroids for complete resolution. The patients usually have demonstrable Gram-negative or Gram-positive infection, of non-cutaneous origin, and underlying systemic disease. Vacuolopathic necrosis of epidermal keratinocytes, and damaged vascular endothelium of the dermal blood vessels can be demonstrated by light and electron microscopy, as well as by lectin studies. Immunocytochemical studies reveal the presence of activated macrophages and T lymphocytes. We believe the syndrome is due to lipopolysaccharide-induced or bacterial mitogen-induced tumour necrosis factor-alpha (TNF-alpha), secreted by previously primed activated macrophages in a second-set response. TNF-alpha characteristically injures endothelial cells and epidermal keratinocytes. It is thought to induce its cytotoxic effects partly via neutrophil degranulation, and partly via DNAase activation, with resultant DNA fragmentation and cell lysis. Corticosteroids have been shown not only to inhibit TNF-alpha secretion by activated macrophages, but also to block its cytotoxicity, thus accounting for the extremely rapid clinical response to this drug in conjunction with adequate and appropriate antibiotic therapy.

Expression of the CD54 (ICAM-1) and CD11a (LFA-1) adhesion molecules in oral mucosal inflammation

Previous studies of chronic dermatoses have suggested that expression of the CD54 cell surface antigen (intercellular adhesion molecule-1, ICAM-1) by keratinocytes is a feature of chronic inflammation. However, whether such expression is a prerequisite for intraepithelial migration of lymphocytes is unclear. The present study evaluated the expression of CD54 and its ligand, CD11a (lymphocyte function-associated antigen, LFA-1) in oral lesions of lichen planus, recurrent aphthous stomatitis, secondary Sjögren's syndrome and traumatic ulceration using an immunoperoxide technique. In 33 of 56 lesions examined, substantial numbers of CD11a + cells were present within oral mucosal epithelium despite an absence of detectable keratinocyte CD54 antigen expression. Consequently, CD54/CD11a adhesion interactions may not be critical in the initiation of oral mucosal inflammation.

Electron microscopic and immunocytochemical studies of the sequence of events in psoriatic plaque formation following tape-stripping

Electron microscopic and immunocytochemical studies were performed on sequential biopsies following the tape-stripping of the uninvolved skin in 12 patients with psoriasis. In the biopsies taken after 5 min for up to 7 days during the pre-psoriatic phase, there were initial lymphocyte-Langerhans cell interactions as well as interactions between lymphocytes and keratinocytes. In biopsies taken after 6-8 weeks during the proliferative phase there were lymphocyte-macrophage interactions. In the 24-h and 7-day biopsies there were close contacts between epidermal lymphocytes and keratinocytes via microvilli, with blebbing of the keratinocyte plasma membranes and granular cytoplasmic changes around these microvilli. Few basal keratinocyte herniations were noted during this phase. The 6-8-week biopsies of Köbner-positive patients were characterized by a marked increase in lymphocyte-macrophage interactions via similar microvillous processes with associated electronlucent areas suggestive of cytotoxicity.

Efficacy of cyclophosphamide in toxic epidermal necrolysis. Clinical and pathophysiologic aspects

In this article we describe the immunocytochemical and electron microscopic findings in five patients with toxic epidermal necrolysis. They indicate the occurrence of necrotic keratinocytes with nuclear disintegration associated with apposed dendritic cells with the nuclear chromatin configuration of T lymphocytes. These findings, including the presence of blebbing of the keratinocytes and membrane defects associated with cytoplasmic processes from these apposed lymphoid cells, fit known electron microscopic criteria that suggest the involvement of T lymphocyte-mediated cytolysis of drug-altered target keratinocytes in toxic epidermal necrolysis. The effector cell appears to be a dendritic subset, with the phenotypic characteristics (CD3+, CD4-, CD8+, CD2+, DR+) of a T cell subset. There is some evidence that tumor necrosis factor alpha, secreted by activated macrophages, may play a role in necrolysis of the epidermis. The dramatic response of our patients to cyclophosphamide, which is known to inhibit cell-mediated cytotoxicity by inhibiting both the recognition and lethal hit stages, together with the rapid regrowth of the epidermis within 4 days to a week in patients who received adequate dosage of the drug, supports the preceding concepts.

Blood mononuclear cells from patients with psoriasis exhibit an enhanced adherence to cultured vascular endothelium

Blood mononuclear cells (MNC) from patients with psoriasis were more adherent to monolayers of endothelial cells prepared from human umbilical cord vein than otherwise similar cells from control subjects. This increase in adherence occurred in the presence (mean 37% increase; p less than 0.01) and absence (mean 47% increase; p less than 0.05) of 10% autologous serum and was not related to the disease severity of the patients. The augmented adhesiveness of the patients' cells was also apparent when using monolayers of endothelial cells isolated from human skin. The levels of immune complexes, complement, alpha 2-macroglobulin, acute phase proteins (alpha 1-acid glycoprotein, C-reactive protein and alpha 1-antitrypsin), and tumor necrosis factor alpha (TNF alpha), interleukin-1 alpha (IL-1 alpha), and interleukin-1 beta (IL-1 beta) in the patients' sera were within normal limits. When MNC were added to endothelial monolayers that had been incubated with either TNF alpha or the highest concentration of rIL-1 beta used in the study, both the patients' and control's cells exhibited a similar increase in attachment (p less than 0.01). Pretreatment of endothelium with interferon-gamma did not enhance the attachment of MNC from either group of subjects. The augmented adherence of the patient's MNC appears to be due to an abnormal adhesiveness of the lymphocytes rather than the monocytes and is not related to an enhanced expression of the cell-surface adhesion molecules CD11a/CD18. It is likely that the circulating MNC of psoriatic patients may be predisposed for extravasation into skin.

Predominance of CD8 subset in id eruption of poison oak-induced dermatitis

The pathophysiology and immune mechanisms involved in the clinical syndrome of autoeczematization remain a mystery. In this study of nickel dermatitis without autoeczematization and poison oak dermatitis with autoeczematization, it was noted that the process of autoeczematization was associated with the presence of CD8+ lymphocytes within the epidermis and the expression of HLA-DR antigens on epidermal keratinocytes. It is surmised that since CD8+ clones are induced by poison oak antigen but not by nickel, the inability of nickel to induce CD8+ lymphocytes may explain why uncomplicated nickel dermatitis does not autoeczematize. Since the selective adherence of CD8+ lymphocytes to keratinocytes, probably via the expression of adhesion molecules such as ICAM-1, the generation of antigens on endothelial cells of high endothelial venules involved in lymphocyte trafficking, and the expression of HLA-DR antigens on epidermal keratinocytes are all due to the activity of interferon-8, it is deduced that this lymphokine may play a key role in id eruptions induced by contact allergens.

Immunologic interactions of T lymphocytes with vascular endothelium

The data presented in this review establish that cultured human endothelial cells have the capacity to present antigens to T cells and to do so in the context of costimulators that lead to effective T cell activation. These activities raise the possibility that venular ECs, at sites of delayed hypersensitivity reactions, could be the primary antigen-presenting cell to circulating memory T cells. This putative role of ECs can explain the rapid rate of initiation of memory responses because ECs are uniquely positioned to have physical access to the pool of circulating memory T cells. Studies also suggest that ECs may present alloantigens to circulating T cells in the context of transplantation, thereby initiating rejection reactions. Nevertheless, we repeat our caveat that these proposed antigen-presenting functions of ECs have not been established in vivo. Cytokine-mediated changes, particularly induction of adhesion molecules and synthesis of lymphocyte-activating cytokines, such as IL-8, provide ECs with the potential to recruit memory T cells to inflammatory sites independent of antigen specificity. Although these functions have also not been rigorously shown to occur in vivo, immunocytochemical studies of experimental and pathological tissues provide significant support for this proposal. Similar adhesive and activating functions of ECs may apply to preferential homing of pre-T cells to thymus and naive T cells to lymph node. We conclude by noting that the weight of evidence reviewed here supports the proposal that the vascular endothelium be considered an integral part of the in vivo immune system.

Effects of rIFN alpha, beta, and gamma on the morphology, proliferation, and cell surface antigen expression of human dermal microvascular endothelial cells in vitro

The influence of recombinant human interferon alpha 2a (rIFN alpha), recombinant human interferon beta 1 (rIFN beta), and recombinant human interferon gamma (rIFN gamma) on human dermal microvascular endothelial cells (HDMEC) cultured in vitro was studied in various rIFN concentrations (0.1 IU/ml-10(4) IU/ml) over 2, 3, 4, 6, 8, and 10 d. Cell morphology and ultrastructure, cell proliferation, expression of class II alloantigens (HLA-DR and HLA-DQ), and intercellular adhesion molecule-1 (ICAM-1) were investigated using an in vitro technique established in our laboratory. All rIFN tested induced alterations of typical HDMEC morphology; the cells became spindle-shaped and fibroblastoid, although they maintained their endothelial cell marker expression. Also, all IFN dose- and time-dependently inhibited the proliferation of HDMEC in vitro (rIFN alpha greater than beta greater than gamma), whereby rIFN alpha exerted the strongest growth-inhibitory effect. Alkaline phosphatase anti-alkaline phosphatase (APAAP) immunocytochemistry of the cultured cells showed dose- and time-dependent stimulation of ICAM-1 and class II antigen expression only by rIFN gamma (HLA-DR greater than HLA-DQ), rIFN alpha and beta did not exert any immunomodulatory activity on HDMEC in vitro. These results indicate that HDMEC are an important target for the action of IFN. Besides growth inhibition, it seems that rIFN gamma in particular may be involved in the modulation of leucocyte adhesion and trafficking by altering the immunophenotype of the endothelial cell population.

Tannic-acid staining material on high endothelial venules and lymphocytes in skin and peripheral lymph nodes in Staphylococcus aureus-associated erythroderma

The recognition and binding of glycoprotein receptors on lymphocytes to specific antigens present on high endothelial venules (HEV) precedes the egress of lymphocytes from the blood stream into the tissues. In this paper, we report the presence of HEVs with tannic-acid staining material (TASM+ HEVs) in Staphylococcus aureus-associated erythroderma, which allow the migration of CD8+ lymphocytes from the bloodstream into the epidermis. TASM positivity is also expressed on lymphocytes within the regional lymph nodes, and by intravascular lymphocytes prior to leaving the TASM+ HEV. It is proposed that TASM positivity may represent a molecule, which may function in binding lymphocytes to HEVs prior to egress from the HEV. (TASM is lost from lymphocytes after leaving the HEVs). The expression of TASM positivity may form an essential part of the CD8+ lymphocyte-HEV recognition system, and may be the means whereby CD8+ lymphocytes generated in the regional lymph nodes by various mitogens (in this case by staphylococcal mitogens) may 'home' to specific sites within the epidermis. TASM positivity on both the HEVs and lymphocytes may serve as a convenient marker of such a system.

Interactions between lymphocytes and dermal fibroblasts: an in vitro model of cutaneous lymphocyte trafficking

Cultures of dermal fibroblasts were established from skin biopsies of CBA mice and used to study the interactions with murine T-lymphocytes. Electron microscopy showed that zones of contact developed between the fibroblasts and the T-cells, particularly after mitogenic activation. The adhesion of the lymphocytes was temperature-dependent, and many more lymphoblasts than resting cells attached to the fibroblast monolayers. Flow cytometry analysis of the adherent population showed that the most prominent type of resting lymphocyte was of the CD4 phenotype, which was also observed using a T-helper lymphoid cell line. However, neither the CD4 nor the CD8 (T-cytotoxic) antigens were involved in the binding process, and while the fibroblasts expressed Class I MHC molecules (but not Class II), these also had no role in mediating lymphocyte adhesion. Although the fibroblasts did not express the ligand Mala-2, the murine homologue of human ICAM-1, a monoclonal antibody against LFA-1, its cognate receptor on the lymphocytes, nevertheless effectively inhibited binding. T-cell attachment was also partially prevented by antibody against the lymphocyte CD2 antigen and by RGDS, a protein epitope known to mediate a number of receptor-integrin interactions. Moreover, this peptide also rapidly and preferentially detached T-lymphocytes which had previously adhered to the fibroblast monolayers. Lymphocyte binding was substantially elevated following treatment of the fibroblasts with cytokines such as tumor necrosis factor-alpha and interferon-gamma, but not interleukin-1 alpha. This increase in adhesiveness was, however, almost completely abolished by monoclonal antibodies specific for LFA-1 or for Mala-2. The results of this study show that while lymphocytes recognize fibroblasts normally via a number of constitutively expressed receptor-integrin interactions, their adhesion can also be modulated by cytokine-induced changes in the expression of other surface ligands.

The role of adhesion molecules, chemotactic factors, and cytokines in inflammatory and neoplastic skin disease--1990 update

In 1986 it was discovered that cultured human keratinocytes, when treated with gamma interferon, attract and bind T lymphocytes and monocytes. More is now known about trafficking of inflammatory cells in the skin, with specific molecular details involving various cytokines, chemotactic factors, and adhesion molecules. One key element is the in vivo movement of T cells that express LFA-1 into the epidermis, and their subsequent binding to keratinocytes via the surface expression of intercellular adhesion molecule-1 (ICAM-1). This interaction represents a common immunologic pathway, which has been identified in a wide variety of different skin diseases. This review provides a synopsis of advances in this field, which have grown rapidly during the past few years, and adds recent results dealing with coordinate regulation at the gene-transcriptional level of keratinocyte chemotactic factor production and adhesion molecule expression. Moreover, epidermal keratinocytes appear to play a pre-eminent role in the skin, serving as transducing elements converting exogenously applied low-molecular-weight chemical stimuli such as phorbol ester and urushiol (the active ingredient in poison ivy extracts) into the production of endogenously derived immunoregulatory proteins. These keratinocyte-derived molecules may then influence immunocytes and endothelial cells to further amplify the inflammatory response. The identification of keratinocyte-derived molecules such as IL-8 and ICAM-1, which influence the chemotaxis and adherence of T cells, adds substantial evidence supporting an active participatory role for keratinocytes in cutaneous immunohomeostasis. Finally, we highlight the importance of these immunoregulatory molecules in two malignant cutaneous disorders (cutaneous T-cell lymphoma and basal-cell carcinoma) and attempt to integrate these new findings into novel pathophysiologic models for two inflammatory dermatoses (rhus dermatitis and psoriasis).

Immunopathological aspects of etretinate therapy in lichen planus

Biopsy specimens of involved and uninvolved skin were studied in 8 patients suffering from generalized lichen planus (LP) before and after successful etretinate treatment using murine monoclonal antibodies against several cell surface markers of effector and/or accessory cells of the immune system. In contrast to untreated LP-lesions, in biopsies obtained after etretinate therapy from healed involved skin a markedly disintegrated HLA-DR expression on keratinocytes and intraepidermal Langerhans cells and a nearly total loss of suppressor/cytotoxic T lymphocytes at the dermo-epidermal interface were found. Our data emphasize the key position of the class II antigen expression on various immunocompetent cells, as a marker for a cell-mediated immune reaction, on the other hand, stress the involvement of keratinocytes, Langerhans cells and suppressor/cytotoxic T lymphocytes in the pathogenesis of LP.

Cyclic adenosine monophosphate levels and the function of skin microvascular endothelial cells

The maintenance of the normal epithelioid morphology of human dermal microvascular endothelial cells (MEC) grown in vitro depends strongly on the presence of factors that increase intracellular levels of cyclic AMP. Complete removal of dibutyryl cAMP and isobutylmethylxanthine (IMX) from the growth medium results in a progressive transition from an epithelioid to a spindle-shaped cell line. This transition cannot be reversed by the readdition of dibutyryl cAMP and IMX to the growth medium or by addition of agonists that increase cAMP levels. Spindle-shaped MEC lose the ability to express Factor VIII rAG and DR antigens and to bind peripheral blood mononuclear leukocyte (PBML). Ultrastructural analyses of transitional cells and spindle-shaped cells show decreased numbers of Weibel-Palade bodies in transitional cells and their complete absence in spindle-shaped cells. Interferon-gamma alters several functional properties of both epithelioid and spindle-shaped cells. In the absence of dibutyryl cAMP it accelerates the transition from epithelial to spindle-shaped cells, whereas in the presence of cyclic AMP interferon-gamma increases the binding of PBMLs to both epithelioid and spindle-shaped MEC and the endocytic activity of the endothelial cells. These results suggest that cyclic AMP is an important second messenger in the maintenance of several key functions of microvascular endothelial cells. Factors that influence the levels of this messenger in vivo can be expected to influence the angiogenic and immunologic functions of the microvasculature.

Intercellular adhesion molecule expression in the evolving human cutaneous delayed hypersensitivity reaction

Intercellular adhesion molecule-1 (ICAM-1), putatively expressed by antigen-presenting or target skin cells, is a ligand for the lymphocyte function-associated antigen (LFA-1) present on circulating lymphocytes. Immunohistochemistry of normal adult human skin using monoclonal antiserum to ICAM-1 demonstrated focal reactivity restricted to endothelium lining the dermal microvasculature. Delayed hypersensitivity responses elicited with dinitrochlorobenzene in the skin of the same subject were evaluated sequentially over a 96 h period using immunohistochemical and ultrastructural techniques. The first alteration observed consisted of mast cell degranulation within perivenular foci in the superficial dermis at 4 h after antigen challenge. Sparse superficial perivascular T-cell infiltrates were present by 24 h. Progressive staining for ICAM-1 was observed in microvascular endothelium and in dermal dendritic cells between 24 and 48 h. ICAM-1 expression was documented focally within the lower epidermis at 48 h and diffusely within the lower and upper epidermal layers at 96 h. ICAM-1 expression by keratinocytes was consistently associated with T-cell migration into the epidermis, whereas migration was never observed in the absence of ICAM-1 reactivity. Immunoelectron microscopy confirmed ICAM-1 to be exclusively present on endothelial cells, dermal dendritic cells, mononuclear cells, and keratinocytes, and permitted characterization of the patterns of membrane reactivity. ICAM-1 expression by epidermal cells appears to be closely linked to the progressive migration of T cells from the dermis into the epidermis that characterizes cutaneous delayed hypersensitivity.

Microvascular endothelial cell culture

Microvascular endothelial cells play a central role in inflammation, tumor metastasis, and wound healing. Methods to study these processes in vitro using cells isolated from adult skin, from the inner and the outer segments of the neontal foreskin, and from experimental animals are reviewed. A new modified Iscove's medium supplemented with 2% pre-partum maternal serum, dibutyryl cyclic AMP, isobutyl methylxanthine, thymidine, and hypoxanthine is described. This modified medium supports growth of both adult and neonatal endothelial cells up to seven passages with retention of cytologic markers closely identified with endothelial cells (Weibel-Palade bodies, Factor VIII-associated antigen). Several functions associated with the microvasculature in situ are expressed by microvascular endothelial cells in cell culture. Such functions include the formation of a basement membrane, angiogenesis, intercelluar gap formation in response to vasoactive agents, and the attachment and migration of lymphocytes through endothelial monolayers.

T lymphocytes and monocytes bind to keratinocytes in frozen sections of biopsy specimens of normal skin treated with gamma interferon

When 2 mm punch biopsy specimens of normal skin are incubated with gamma interferon (IFN-gamma), the keratinocytes are induced to express intercellular adhesion molecule-1 (ICAM-1). Lymphocytes and monocytes that express lymphocyte function-associated antigen-1 (LFA-1) bind to cultured keratinocytes expressing ICAM-1. We have developed an in vitro adherence assay using frozen sections of normal skin that have been incubated with IFN-gamma, and then overlaid by peripheral blood mononuclear leukocytes. Although peripheral blood mononuclear leukocytes do not bind to the epidermal keratinocytes of untreated skin sections, after exposure of the skin to IFN-gamma the peripheral blood mononuclear leukocytes prominently bind to the epidermal keratinocytes that express ICAM-1. The binding by peripheral blood mononuclear leukocytes is increased approximately twofold by activation with phorbol ester treatment. The temperature dependence and kinetics of this adherence reaction reveal no binding at 8 degrees C, good binding at 24 degrees C, and optimal binding at 37 degrees C, reaching a maximal extent by 60 minutes. The adherence reaction is blocked either by pretreating the peripheral blood mononuclear leukocytes with LFA-1 antibody or the IFN-gamma-exposed skin specimen with ICAM-1 antibody. The immunophenotypic analysis of the adherent peripheral blood mononuclear leukocytes to epidermal keratinocytes revealed that most cells activated by 12-O-tetradecanoyl-phorbol-13-acetate are T lymphocytes, with CD8+ T cells binding slightly better than CD4+ T cells, with a smaller population of monocytes. These results provide additional support for a role of LFA-1, ICAM-1, and IFN-gamma in modulating keratinocyte-lymphocyte interactions.(ABSTRACT TRUNCATED AT 250 WORDS)

Adhesion molecule mapping in normal human skin

Adhesion molecules are a rapidly growing group of cell surface receptors providing cell-cell and cell-matrix interactions. Their physiological role in tissue homeostasis as well as cellular migration and differentiation is increasingly appreciated. In the present study we have analyzed the expression pattern of most adhesion molecules of the integrin family as well as of adhesion molecules belonging to the immunoglobulin superfamily in normal human skin. We provide evidence that expression of adhesion molecules in the various cutaneous cell systems follows a constant distribution. Moreover, the physiological mononuclear infiltrate of the skin also expresses a variety of adhesion molecules enabeling these cells to migrate or to reside within the skin. Furthermore, our results indicate that intercellular adhesion molecule-1 is not a prerequisite for lymphocyte epidermotropism as frequently stated. Our data provide a rational basis to analyze changing adhesion molecule expression in inflammatory and neoplastic skin diseases.