Shortened telomere length is demonstrated in T-cell subsets together with a pronounced increased telomerase activity in CD4 positive T cells from blood of patients with mycosis fungoides and parapsoriasis

We have recently demonstrated that telomerase activity is increased and telomere length shortened in lymphocytes from peripheral blood of patients with cutaneous T-cell lymphoma. In order to determine which cell type has increased telomerase activity and shortened telomere length, CD4+, CD8+, CLA+ CD3+ and CLA- CD3+ T cells were isolated from peripheral blood of 25 patients, including 15 patients with mycosis fungoides and 10 patients with parapsoriasis. Eleven healthy individuals were used as controls; CD19+ B cells were separated from each individual as an internal control. The results showed that the increased telomerase activity was significantly predominating in the CD4+ T-cell subset. Significantly shortened telomere length was found in CD4+ and CD8+ T-cell subsets from the patients compared with the same cell subsets obtained from healthy individuals. However, no difference was observed between the subsets; CD19+ B cells collected from patients and healthy control individuals had similar telomerase activity and telomere length which was significantly different from the values found in T cells. The telomere length was significantly shorter in CLA+ CD3+ subset than in CLA- CD3+ subset. Interestingly, increased telomerase activity and shortened telomere length was also detected in CD4+ T cells from patients with parapsoriasis indicating that alteration of telomerase activity and telomere length in CD4+ T cells is an early event in the pathogenesis of cutaneous T-cell lymphoma. Thus, the results indicate that a significant high level of telomerase activity and shortened telomere length frequently occur in T cells of patients with CTCL and may reflect tumorigenesis.     

Phenotypic determination of T-lymphocytes responding to chemotactic stimulation from fMLP,IL-8, human IL-10, and epidermal lymphocyte chemotactic factor

Summary Human T lymphocytes were collected after they had migrated towards N-formyl-methionyl-leukyl-phenylalanine (fMLP), rIL-8, human IL-10 (hIL-10), and epidermal lymphocyte chemotactic factor (ELCF). They were stained for determination of their phenotype by FACS analysis using anti-CD4, -CD8, -CD18, -CD45R0 and OPD4 antibodies. Human IL-10 increased the percentage of CD8⁺ T lymphocytes in the migrating cell population by 152% compared with cells migrating towards the medium and decreased the number of CD4⁺ T lymphocytes by 79%. ELCF increased the number of CD4⁺ T lymphocytes by 18%, and the number of CD45R0⁺ T lymphocytes by 52%, while the number of CD8⁺ T lymphocytes was decreased by 20%. rIL-8 increased the number of CD4⁺ T lymphocytes and decreased the CD8⁺ T lymphocytes. The distribution of the different subpopulations of T lymphocytes was not changed significantly by fMLP. The observed changes in the phenotypes did not occur when incubating T lymphocytes with the chemotaxins. Our observations demonstrate that individual chemotactic factors will attract specific subsets of T lymphocytes. They may help to explain the predominance of memory T lymphocytes (CD4R0⁺, CD4⁺) in allergic contact dermatitis and certain other skin diseases. They also confirm the results of a recent study, that showed hIL-10 to be selectively chemotactic for CD8⁺ T lymphocytes.     

CD4+ T cells producing interleukin (IL)‐17, IL‐22 and interferon‐γ are major effector T cells in nickel allergy

Background It has been suggested that interleukin (IL)‐17 and IL‐22 play important roles in the elicitation of human allergic contact dermatitis; however, the frequencies of T cell subtypes producing IL‐17 and IL‐22 in human allergic contact dermatitis are unknown. Objectives To determine the frequencies of CD4⁺, CD8⁺ and γδ T cells producing IL‐17, IL‐22 and interferon (IFN)‐γ in the blood and skin from nickel‐allergic patients. Patients/materials/methods Blood samples were collected from 14 patients and 17 controls, and analysed by flow cytometry. Biopsies were taken from 5 patients and 6 controls, and analysed by immunohistochemistry and flow cytometry of skin lymphocytes. Results We found an increased frequency of γδ T cells in the blood, but no differences in the distribution of cytokine‐producing CLA⁺ T cell subtypes in nickel‐allergic patients as compared with controls. In nickel‐allergic patients, there was massive cellular infiltration dominated by CD4⁺ T cells producing IL‐17, IL‐22 and IFN‐γ in nickel‐challenged skin but not in vehicle‐challenged skin. Conclusion CD4⁺ T cells producing IL‐17, IL‐22 and IFN‐γ are important effector cells in the eczematous reactions of nickel‐induced allergic contact dermatitis in humans.     

Expression of CD30 on T helper cells in the inflammatory infiltrate of acute atopic dermatitis but not of allergic contact dermatitis

Abstract  The CD30 molecule has been proposed as a marker for a subset of CD4⁺CD45RO⁺ (memory) T cells with potent B cell helper activity producing IL-5 and IFN-γ and as a specific marker for Th2 cells. Recently, an association has been demonstrated between elevated serum levels of soluble CD30, which is shed by CD30⁺ cells in vitro and in vivo, and atopic dermatitis but not respiratory atopic disorders or allergic contact dermatitis. We studied the expression of CD30 in the inflammatory infiltrate of atopic dermatitis compared with that of allergic contact dermatitis, with special regard to skin disease activity (acute vs subacute/ chronic). Biopsies were obtained from 16 patients suffering from atopic dermatitis (acute n = 6, subacute/ chronic n = 10), from 7 patients with acute allergic contact dermatitis and from 5 positive patch-test reactions. Paraffin-embedded as well as snap-frozen material was stained with anti-CD30 and anti-CD45RO mAbs according to standard procedures. Double-staining procedures for CD30CD3, CD30CD4, CD30CD45RO and CD30CD68 were also performed. Abundant CD45RO⁺ cells were detected both in atopic dermatitis and in allergic contact dermatitis lesions. We found scattered CD30⁺ cells in only one of six formalin-fixed paraffin-embedded acute atopic dermatitis biopsies, but in all of the respective snap-frozen specimens, possibly because CD30 expression on atopic dermatitis infiltrating cells is weak and sensitive to formalin fixation and paraffin embedding. CD30CD3 and CD30CD4 double staining identified CD30⁺ cells to be helper T lymphocytes. No significant CD30 expression (either in paraffin-embedded or in frozen material) could be found in subacute/chronic atopic dermatitis lesions or in any of the specimens of allergic contact dermatitis. The results suggest a specific regulatory function of CD30⁺ T cells in acute atopic dermatitis. With respect to the view that CD30 is a marker for Th2 cells, our observations confirm previous findings that Th2 cells predominate in the infiltrate particularly of acute atopic dermatitis. CD30 expression in acute atopic dermatitis but not in acute allergic contact dermatitis might be helpful in the histological differentiation of these disorders and in the further characterization of atopy patch testing. Received: 1 April 1998 / Received after revision: 28 May 1998 / Accepted: 3 July 1998     

CD4+ and CD8+ T cells mediated direct cytotoxic effect against Trichophyton rubrum and Trichophyton mentagrophytes

Background The cellular immune system is the most dominant factor in curing acute dermatophytosis. However, the exact immune mechanisms involved in generating this defense are complex and still obscure. The aim of this study was to investigate the fungicidal mechanism of T cells in the normal population versus patients with chronic fungal infections. Methods Thirty patients were included in the study: 15 patients with chronic dermatophytosis and 15 normal healthy patients with a history of acute dermatophytosis. The procedures were performed as follows. 1) Proliferation and cytotoxic activity of lymphocytes cultured with various dermatophytes homogenate such as, Trichophyton rubrum, Trichophyton mentagrophytes and Microsporum gypseum. 2) CD4⁺ and CD8⁺ T cells were separated by magnetic beads before culture with fresh spores of either T. mentagrophytes or T. rubrum. 3) Routine histology and ultrastructural study were performed to illustrate the mode of activity of the T cells against the dermatophytes. Results The study showed that both CD4 and CD8 possess cytotoxic activity against dermatophytes. However, the results demonstrated a suppression of lymphocyte proliferation response and a significant lower cytotoxic effect in chronic patients. Ultra structure and histological evaluation of the culture of hyphae with CD4⁺ or CD8⁺ T cells showed more prominently destructive effects in the culture of cells that had been obtained from normal population than those of patients with long‐lasting fungal infections. Conclusion The study suggests a selective impairment of lymphocyte function against dermatophytes, in patients with chronic dermatophytoses.     

Characterization of the T cell response in allergic contact dermatitis caused by corticosteroids

Background Delayed allergic hypersensitivity reactions have classically been described as type IV reactions, which are caused by T cells; however, the respective roles of CD4⁺ and CD8⁺ cells are yet to be defined. A central role for CD8⁺ cytotoxic T cells as effector cells has been suggested. Objectives To determine the type of T cell involved in corticosteroid allergy. Methods We analysed the kinetics of T cell recruitment and the cytokine production profile in positive patch tests of 27 corticosteroid‐sensitized patients, as compared with control sites and control subjects. Skin biopsies, collected at 8, 24 and 48 hr following drug application, were embedded in paraffin for histological and immunohistological staining, and, in some cases, also deep‐frozen for gene expression analyses. Results CD3⁺ T cells were rapidly recruited in concert with the positivity of the patch test sites. High levels of interleukin (IL)‐4, IL‐5 and, to a lesser extent, interferon‐γ suggested that both Th2 and Th1 cytokines were implicated. IL‐4 was also produced by γδ T cell receptor (TCR) lymphocytes. Conclusions This study showed that, in allergic contact dermatitis caused by corticosteroids, the inflammatory infiltrate is composed of CD3⁺ T cells with a predominant Th2 cytokine profile, among which IL‐4 is also produced by γδ TCR lymphocytes.     

Possible role of superantigens in inducing autoimmunity in pemphigus patients

The diagnostic and pathological relevance of anti‐desmoglein autoantibodies in common forms of pemphigus has been well established, and T cells have been shown to play a role in the onset and progression of these diseases. The role of superantigens in provoking polyclonal activation of T cells with many different fine specificities, possibly including autoreactive T cells and T‐cell mediated autoantibody response, is unknown. Further, abnormal T‐cell function may lead to opportunistic infections particularly with Candida. The response of T cells of pemphigus patients to recall antigens of these opportunists is not clear. The aim of this study was to investigate the in vitro response of T lymphocytes from pemphigus patients to common bacterial superantigens such as streptococcal pyrogenic exotoxin A and staphylococcal enterotoxin B, and recall antigens such as Candida antigen. Changes in CD3⁺CD4⁺ and CD3⁺CD8⁺ T‐cell sub‐populations and expression of naive/memory markers (CD45RA⁺/RO⁺) on different T cells were analyzed by flow cytometry. Significant elevation in CD3⁺CD4⁺ and expression of the memory (CD45RO⁺) markers on these cells was observed both in pemphigus vulgaris and pemphigus foliaceus patients, as compared to healthy controls, upon stimulation with streptococcal pyrogenic exotoxin A and staphylococcal enterotoxin B. However, only memory T cells (CD45RO⁺) were significantly increased upon Candida antigen stimulation. Our study suggests that CD4⁺ memory T lymphocytes may modulate the pathogenic autoantibody response in pemphigus patients, and also emphasizes the possibility that the superantigen‐reactive T cells participate in the triggering of autoimmunity in pemphigus.     

T cells migrate to tumour sites after extracorporeal interleukin 2 stimulation and reinfusion in a patient with metastatic melanoma

Peripheral blood mononuclear cells (PBMC) were taken by leukapheresis from a patient with melanoma skin metastases and stimulated in vitro using 1000 IU recombinant interleukin 2 (IL-2)/ml to generate lymphokine-activated killer cells (LAK cells). Two-colour immunofluorescence analysis demonstrated an IL-2-induced up-regulation of CD25 on natural killer cells (CD56⁺) as well as on T lymphocytes (CD3⁺). After radiolabelling with indium-111, the cells were reinfuse. Gamma-camera imaging revealed an enrichment at the tumour sites. Immunostaining of tumour tissue taken before and after scintigraphy demonstrated CD25⁺ Tlymphocytes (CD2⁺, CD3⁺), but no natural killer cells (CD16⁺, CD56⁺) infiltrating the metastases. LAK cell enrichment at melanoma metastases in vivo did not involve natural killer cells, but was characterized by increased numbers of activated T lymphocytes in this patient.     

The importance of CD54 and CD86 costimulation in T cells stimulated with Candida albicans and Dermatophagoides farinae antigens in patients with atopic dermatitis

Abstract A number of studies have demonstrated an increased frequency of allergen-specific T cells producing increased amounts of interleukin-4 (IL-4) and IL-5, but little interferon-γ in both the peripheral blood and skin lesions of patients with atopic dermatitis (AD). In this study, to further clarify the characteristics of T cells obtained from AD patients, we examined the dependency of the antigen-specific proliferation of peripheral blood mononuclear cells (PBMC) from AD patients on costimulatory molecules. The antigens used were Candida albicans and Dermatophagoides farinae, for which AD patients show increased levels of IgE antibodies. PBMC from control healthy donors stimulated with these antigens incorporated [³H]-thymidine much more than PBMC from AD patients. The addition of anti-CD54, -CD40, -CD80 and -CD86 monoclonal antibodies to the cultures showed that the PBMC required only CD54 and CD86 for stimulation with C. albicans, but required CD54, CD80 and CD86 for stimulation with D. farinae. Among these monoclonal antibodies, the anti-CD54 antibody suppressed the proliferative responses of most PBMC, most effectively followed by the anti-CD86 antibody. However, there were no significant differences in the requirement for costimulatory molecules of PBMC proliferation stimulated with C. albicans or D. farinae between AD patients and healthy donors. Since many studies have suggested that T-helper type 1 and T-helper type 2 immune responses are different in their dependency on CD80 or CD86 costimulation, our present results suggest that the allergen-specific T cells of AD patients are not completely shifted to a T-helper type 2 subset. Received: 10 February 1998 / Received after revision: 2 July 1998 / Accepted: 2 July 1998     

Reduction of skin-homing cytotoxic T cells (CD8+ -CLA+) in patients with vitiligo

Background: Vitiligo is a frequently acquired, hereditary disease, characterized by achromic macules due to the absence of melanocytes. In contrast with earlier studies, in which the main pathogenic role was attributed to anti‐melanocyte antibodies, recent papers have emphasized a role for CD8⁺ cytotoxic T lymphocytes in melanocyte destruction. Fifteen percent of peripheral T cell express cutaneous lymphocyte‐associated antigen (CLA), responsible for skin‐homing T cell. Phototherapy is used to treat patients with generalized vitiligo and it has been shown to interfere with CLA⁺ T cells in other skin diseases. Objective: To describe peripheral blood T cell subpopulations' frequency and ability to express the skin‐homing molecule (CLA) in patients with non‐segmental vitiligo, before and after photochemotherapy (PUVA). Patients and Methods: Twenty‐two patients with generalized and active spreading vitiligo were submitted to 30 PUVA‐8MOP sessions. Lymphocyte immunophenotyping was performed by flow cytometry using anti‐CD3, anti‐CD8 and anti‐CLA monoclonal antibodies. Fifteen healthy volunteers, sex‐ and age‐matched, were included as a control group. Results: CD8⁺–CLA⁺ T cells were significantly reduced in number in untreated vitiligo patients (P=0.008) when compared with control individuals, albeit with a more intense CLA expression (P=0.028). These findings were not altered after PUVA. No significant difference was noticed in CD4/CD8 ratios nor in CD4–CLA⁺ T cell numbers between vitiligo patients and controls, both before and after PUVA. Conclusions: CD8–CLA⁺ T cells are reduced in peripheral blood of patients with non‐segmental vitiligo. This finding may be related to the previously reported increase of CD8⁺ cells in both lesions and perilesional skin of these patients.     

CD8+ cytolytic T lymphocytes and the skin

Abstract: T lymphocytes show a special affinity for the skin. Although the roles played by the CD4⁺ population of T lymphocytes in immunodermatology were so far actively investigated, much less is known about the roles played in the skin by CD8⁺ cytolytic T lymphocytes (CTL). The activity of CD8⁺ CTL in the immunodermatological context, however, is likely to be most important; the immuno-biology itself of CD8⁺ CTL, moreover, although far from being fully understood, shows intriguing characteristics. Immunophenotype, function and cytokine profile of CD8⁺ CTL are overviewed in the first section of this review. Phenotypically, not only CD8⁺ CTL can be subdivided into CD8⁺ CD28⁺ CD11b⁺ and CD8⁺ CD28^- CD11b⁺ subsets, but also an up-to-now undetected CD8⁺ CD28^- CD11b^- subset does exist. Functionally, not only “cytotoxic” but even “suppressor” subpopulations have been shown to exert cytolytic capabilities indeed, and “suppression” itself may be due to such a lytic capacity. According to cytokine synthesis, CD8⁺ CTL can be split into Tc1 and Tc2 subsets, each able to influence specific patterns of immune responses. The impact of CD8⁺ CTL in immunodermatology, overviewed in the second section of the current review, is crucial. The pathophysiology of inflammatory dermatoses is deeply influenced by the activity of CD8⁺ CTL: e.g., CD8⁺ CTL within psoriateic epidermis are possibly associated to the persistence of psoriatic lesions not undergoing resolution; on the other hand, in late lesions of lichen planus CD8⁺ CTL predominate, thus explaining presumably both the cytolytic attack against keratinocytes and the modulation of the inflammatory reaction up to the final resolution of the lesions; Tc1 cells are decreased in atopic dermatitis, and such a decrease can account both for IgE overproduction and for development of infections. Finally, CD8⁺ CTL can sustain against cutaneous viruses/tumors cytolytic immune responses not only of secondary but even of primary type, i.e. induced by Langerhans cells/dendritic cells either transfected or pulsed with skin virus/tumor-associated antigens, thus allowing the production of vaccines against cutaneous viral/neoplastic diseases.     

Study of pro‐ and anti‐inflammatory cytokine profile in the patients with parthenium dermatitis

Background: Parthenium dermatitis is a common airborne allergic contact dermatitis induced by exposures to the weed Parthenium hysterophorus. The disease manifests as itchy erythematous papules, papulovesicular and plaque lesions on exposed areas of the body. Objectives: The aim of this study was to show the alterations in pro/anti‐inflammatory cytokines in parthenium dermatitis. Methods: The study included 50 patients with parthenium dermatitis confirmed by patch testing using aqueous extracts of P. hysterophorus and 50 age‐matched healthy controls. The levels of pro‐inflammatory [tumour necrosis factor‐α (TNF‐α), interleukin (IL)‐6, IL‐8, and IL‐17] and anti‐inflammatory (IL‐4 and IL‐10) cytokines were estimated by commercially available high sensitivity enzyme‐linked immunosorbent assay (ELISA) kits. Results: All the dermatitis patients showed significantly (P < 0.001) elevated levels of TNF‐α, IL‐6, IL‐8, and IL‐17 levels as compared to healthy controls. In contrast, the anti‐inflammatory cytokine IL‐4 showed an insignificant decrease (P < 0.217) and a decrease in level of IL‐10 was statistically significant (0.001) compared with controls. Conclusions: The present study suggests the involvement of pro‐inflammatory cytokines in the pathogenesis of parthenium dermatitis. A decrease in levels of anti‐inflammatory cytokines was demonstrated, which could not downregulate pro‐inflammatory cytokines in parthenium dermatitis.     

Influence of aging and cell senescence on telomerase activity in keratinocytes

Telomeres, which exist in eukaryotic chromosome ends in specialized G-rich TTAGGG structure, protect the ends from degradation or fusion. On the other hand, telomerase is a ribonucleoprotein complex enzyme that synthesizes TTAGGG repeat sequences at the ends of eukaryotic chromosomes. Previous studies suggested that telomere length and telomerase activity cooperate in aging and immortalization of cells. Here, we examined telomere length and telomerase activity in keratinocytes from seven human subjects, including a patient with Werner's syndrome. Telomere length in keratinocytes from healthy individuals was shortened with aging. However, telomerase activity from an individual aged 42 years was reduced, compared with that from a 0 year old individual. Passages of keratinocytes reduced telomerase activity significantly in F2 and F3 keratinocytes from 0 and 42 year old individuals. Withdrawal of either EGF or amphiregulin from medium resulted in down-regulation of telomerase activity. These results suggest that telomere length and telomerase activity in primary cultured keratinocytes may be one of the parameters for cell senescence. However, there remain obscure factors such as ultraviolet-B radiation and growth factors.     

Telomerase activity is spontaneously increased in lymphocytes from patients with atopic dermatitis and correlates with cellular proliferation

Telomerase is a ribonucleoprotein enzyme involved with cellular proliferation and cellular senescence. The aim of the present study was to investigate telomerase activity in lymphocytes from patients with atopic dermatitis (AD) and to observe its regulation of cellular proliferation. Peripheral blood mononuclear cells (PBMC) were isolated from 15 patients with AD and 13 healthy donors. Cells were stimulated with purified protein derivative (PPD) of tuberculin (10 microg/ml), interleukin 2 (IL-2) (100 U/ml), anti-CD3 monoclonal antibody (anti-CD3) (1 microg/ml), anti-CD3 plus IL-2, and staphylococcal enterotoxin A (SEA) (0.1 microg/ml). Telomerase activity was measured by the telomeric repeat amplification protocol-based telomerase polymerase chain reaction enzyme-linked immunosorbent assay at 0 and 72 h of incubation. In addition, DNA synthesis of the cells was assayed using 3H-thymidine incorporation. We found that telomerase activity in non-stimulated PBMC from patients with AD was significantly up-regulated without any stimulation during the 72 h of in vitro incubation. The most potent stimulator of telomerase activity was SEA, followed by anti-CD3 plus IL-2, anti-CD3 alone, and PPD. IL-2 did stimulate telomerase activity and DNA proliferation with increasing dosage of IL-2. The DNA proliferation was paralleled by increase in telomerase activity. There was no significant difference between telomerase activity in stimulated lymphocytes from AD patients and normal donors, but the relative increase in telomerase activity tended to be less in AD patients. A spontaneously higher telomerase activity in lymphocytes from AD patients could indicate that T lymphocytes are already stimulated in vivo or that a population of T cells in peripheral blood exhibits an increased telomerase activity compatible with cellular immaturity.     

Selective generation of CD8+ T-cell clones from the peripheral blood of patients with cutaneous reactions to beta-lactam antibiotics

The presence, phenotype, and functional characteristics of peripheral blood penicillin-specific T lymphocytes in individuals with cutaneous allergic reactions to penicillin were investigated using in vitro long-term culture techniques. Peripheral blood mononuclear cells from two penicillin-allergic patients were stimulated in vitro with penicillin, and T-cell blasts were clonally expanded by limiting dilution. Seven T-cell clones were derived, all of which were CD3⁺ CD4^? CD8⁺ HLA-DR⁺, and produced IL-2 and IFN-γ upon stimulation. T-cell proliferation required the presence of antigen and autologous, but not allogeneic, antigen-presenting cells. In addition to the parent compound, the T-cell clones also developed a proliferative response to penicilloyl, the major metabolite of penicillin. The cloned T-cell lines were found to exhibit marked suppressor activity for Con A mitogenesis. The observed suppressor activity required cell-to-cell contact, as supernatants from these T-cell clones had no comparable inhibitory effect. These findings indicate that there is a predominance of penicillin-specific CD8⁺ T cells in the peripheral blood of individuals sensitized to beta-lactam antibiotics.     

Expression of T‐cell immunoglobulin and immunoreceptor tyrosine‐based inhibitory motif domain on CD4+ T cells in patients with atopic dermatitis

The T‐cell immunoglobulin and immunoreceptor tyrosine‐based inhibitory motif domain (TIGIT) is a co‐inhibitory receptor mainly expressed on T cells. Although TIGIT plays an important role in various autoimmune diseases, its role in atopic dermatitis (AD) remains unclear. In this study, we examined the expression levels of TIGIT and their association with clinical features in patients with AD. TIGIT expression on CD4⁺ T cells, central memory T cells, effector memory T cells and regulatory T cells was determined by flow cytometry. CD4⁺ T cells exhibited enhanced TIGIT expression in patients with AD compared with healthy individuals. In particular, effector memory T cells and regulatory T cells, but not central memory T cells, exhibited higher TIGIT expression in patients with AD than in healthy individuals. The frequency of TIGIT⁺ cells among CD4⁺ T cells was significantly increased in patients with mild AD compared with healthy individuals, while decreased in patients with severe AD. Consistently, the frequency of TIGIT⁺ cells among CD4⁺ T cells was negatively correlated with both serum thymus and activation‐regulated chemokine levels and immunoglobulin E levels in patients with AD. Furthermore, TIGIT expression on CD4⁺ T cells inhibited cell proliferation in patients with AD. These results suggest that TIGIT expression on CD4⁺ T cells in patients with AD may be increased to suppress chronic cutaneous inflammation. Moreover, TIGIT expression may be impaired in a subset of patients with AD, leading to a deterioration of skin inflammation. Our study may provide new insight into a TIGIT pathway‐based therapeutic approach for AD.     

The role of perforin-mediated apoptosis in lichen planus lesions

Lichen planus is recognized as a T-cell-mediated disease. Histologically, it is characterized by the formation of colloid bodies representing apoptotic keratinocytes. The apoptotic process mediated by CD8⁺ cytotoxic T lymphocytes (CTLs) and NK cells mainly involves two distinct pathways: the perforin/granzyme pathway and the Fas/FasL pathway. So far, little is known regarding the role of perforin-mediated apoptosis in lichen planus. In the present study, the expression and distribution of perforin, T and NK cell subsets in the epidermis and dermis of lesional and nonlesional lichen planus skin were studied. Skin biopsy specimens from lesional and nonlesional skin of ten patients with lichen planus and eight healthy persons were analysed by immunohistochemistry. Significant accumulation of T cells, particularly of CD4⁺ and CD8⁺ subsets, was found in both epidermis and dermis of lichen planus lesions compared with nonlesional and healthy skin. There were no significant differences in the incidence of NK cells (CD16⁺ and CD56⁺) between lesional, nonlesional and healthy skin. Perforin expression was significantly upregulated in the epidermis of lichen planus lesions. In conclusion, accumulation of perforin⁺ cells in the epidermis of lichen planus lesions suggest a potential role of perforin in the apoptosis of basal keratinocytes.     

Selective Expansions of T cells Expressing Vβ38 and Vβ13 in Skin Lesions of Patients with Chronic Cutaneous Lupus Erythematosus

There are several clinical types of cutaneous lupus erythematosus (LE), including acute cutaneous LE (ACLE), which occurs in 50–60% of patients with systemic LE (SLE), chronic cutaneous LE (CCLE), which is almost the same as discoid LE (DLE), and subacute cutaneous LE (SCLE). Although several important hypotheses have been proposed to explain cutaneous LE, the pathomechanisms still remain complicated and obscure. Of special interest is whether and how the T cell receptor (TCR) repertoire of infiltrating lymphocytes is involved in the development of the different types. To address this issue, we immunohistochemically examined the Vβ usage of infiltrating T cells in skin lesions, as well as in peripheral blood mononuclear cells (PBMC) of patients with cutaneous LE. The number of Vβ3.1 CD3⁺ cells in the PBMC of patients with ACLE and CCLE was significantly lower than in controls. In contrast, the number of Vβ3.1 CD3⁺ cells was elevated in the skin lesion of CCLE over that in psoriasis vulgaris or atopic dermatitis. Furthermore, skin lesions in CCLE patients showed a higher incidence of Vβ8.1 CD3⁺ and Vβ13.3 CD3⁺ cells than did those in ACLE patients. These results suggest that skin lesions of CCLE are oligoclonally associated with selective expansions of TCR Vβ chains and may be induced by antigen stimuli, including superantigens.     

CD8+ dermal T cells from a sulphamethoxazole-induced bullous exanthem proliferate in response to drug-modified liver microsomes

There is evidence that T lymphocytes play a critical role in the pathogenesis of drug-induced bullous exanthems. Sulphonamides are known to be among the most frequent aetiological agents in these severe drug-induced cutaneous hypersensitivity reactions. Several studies indicate that cytochrome P450-dependent metabolites of sulphonamides act as the nominal allergens. A 70-year-old woman with a severe blistering exanthem caused by cotrimoxazole (sulphamethoxazole and trimethoprim) was studied. We employed an in vitro approach to determine whether cytochrome P450-dependent enzymes activated drug-specific T lymphocytes from this patient. Immunohistochemical analysis of involved skin revealed a majority of epidermal CD8⁺ T lymphocytes, whereas the dermal infiltrate was composed of both CD4⁺ and CD8⁺ T cells. Dermal T lymphocytes isolated from lesional skin proliferated in response to sulphamethoxazole, but not to trimethoprim, in the presence of autologous mononuclear cells used as antigen-presenting cells. The antigen-specific response of sulphamethoxazole-specific T cells was significantly augmented in the presence of murine liver microsomes with P450-dependent catalytic activities. Our observations suggest that some cutaneous hypersensitivity reactions to sulphamethoxazole are due to drug-specific T lymphocytes. Cytochrome P450-dependent enzymes may play a critical role in the formation of the nominal antigen, which is recognized by antigen-specific T cells.