CD28 T-cell costimulatory molecule expression in pemphigus vulgaris

Background  CD28 superfamily of immune costimulatory molecules could play an important role in autotolerance control. CD28 costimulation seems to be necessary for regulatory T cell (Treg) activation and successive suppressive activities involved in autoimmunity protection. This study investigates CD28 expression, especially inducible costimulator fraction, on T lymphocytes in pemphigus vulgaris (PV) patients.
Methods  CD28 expression on T lymphocytes was assessed in 16 PV patients during acute attack. All patients and 10 healthy control subjects were tested for lymphocyte populations, T-cell subpopulations (T-CD4⁺, T-CD8⁺), Treg and CD28 expression on T-cell subpopulations.
Results  T, B and natural killer cells average values in PV patients were close to the control group values. Compared with control group, PV values showed lower Treg (2.2% compared with 4.7%), slightly decreased CD4⁺ CD28⁺ T cells (91% compared with 95%), higher CD4⁺ CD28⁻ T cells (9% compared with 5%), decreased CD8⁺ CD28⁺ T cells (57% and 73%, respectively) and significantly enhanced CD8⁺ CD28⁻ T cells (43% compared with 27%).
Conclusions  These data suggest that Treg-mediated suppressor T-cell effects could be diminished in PV, together with an abnormal or ineffective subsequent helper T-cell suppression. CD28 high expression on helper T cells and low expression on suppressor T cells are arguments for a potential CD28 role in PV autoimmune response mechanism.

Conflicts of interest

None declared     

Plasminogen activator system in pemphigus vulgaris

Summary Pemphigus vulgaris (PV) is caused by autoantibodies against desmosomes and is characterized by intra-epidermal blisters. The pathology of PV has been linked with plasminogen activation in lesional epidermis. The plasminogen activator system (PA system) consists of urokinase-type plasminogen activator (uPA). tissue-type PA (tPA). as well as the two types of plasminogen activator inhibitors (PAI-1 and PAI-2). In keratinocytes. uPA binds to a specific cell surface receptor for uPA (uPA-R = CD87) in an autocrine manner. Cell-bound uPA is regulated by PAIs. The central PA system component plasminogen, which is present in plasma and interstitial fluids, is bound to the keratinocyte surface via plasmin(ogen) binding sites, where it can be activated by uPA-R-bound uPA. Cell surface-associated plasmin then mediates pericellular proteolysis. As the topographical organization of the distinct PA system components in lesional epidermis of PV remained elusive, we have performed the present immunohistological analysis of lesional and non-lesional epidermis of PV. In keratinocytes directly involved in the epidermal split formation, plasmin(ogen) was stained in nine of 10 cases, uPA-R and uPA in four of 10 cases and PAI-2 in seven of 10 cases. Together, acantholytic plasmin(ogen)⁺ keratinocytes appeared in three different phenotypes: uPA-R⁺/uPA⁺ and PAI-2⁺, uPA-R^-/uPA^- and PAI-2⁺. as well as uPA-R^-/uPA^- and PAI-2^-. Our findings demonstrate that, in acantholytic keratinocytes of PV. PAs and PAIs appear as differentially regulated components of the PA system.     

Activation of keratinocyte muscarinic acetylcholine receptors reverses pemphigus acantholysis

We studied neuroendocrine mediator regulation of adhesion and motility of human epidermal keratinocytes (EK) and found that cholinergic compounds control EK cell-matrix and cell-cell attachment. In this study, we tested the anti-acantholytic activity of muscarinic agonists in pemphigus and non-pemphigus acantholysis, and investigated the effects of pemphigus antibody (Pab) on the the keratinocyte muscarinic acetylcholine receptors (mAChR). Acantholysis produced by Pab from two patients with pemphigus vulgaris was compared with acantholysis induced by the serine protease trypsin. the calcium chelator EOT A or the muscarinic antagonist atropine. Trypsinized EK first lost contact with microplate surface and then retracted their intercellular filaments. EDTA-treated cells first detached from each other and then from the dish. EK cultures treated with Pab or atropine rounded up and retracted their intercellular filaments simultaneously, although it took hours to obtain acantholysis with Pab treatment compared to several seconds with atropine treatment. Addition of acetylcholine or other muscarinic agonists (bethanechol. carbachol or methacholine) to acantholytic cultures reversed both pemphigus and non-pemphigus acantholysis. Acantholysis induced by atropine reversed spontaneously. Short-term preexposure of EK to Pab significantly increased, and long-term preexposure significantly decreased, the [³H]atropine binding to keratinocyte mAChR. We conclude that muscarinic agonists reverse various types of acantholysis. including acantholysis induced by Pab, and that binding of Pab to EK may affect the ability of keratinocyte mAChR to bind its ligands.     

Clinical effectiveness and safety experience with alefacept in the treatment of patients with moderate-to-severe chronic plaque psoriasis in Taiwan: results of an open-label, single-arm, multicentre pilot study

Background  The effectiveness and safety of alefacept for the treatment of moderate-to-severe chronic plaque psoriasis has been established in several clinical trials conducted in the United States and Europe. No clinical trial of alefacept has been conducted in Asia.
Objective  To determine the effectiveness and safety of alefacept in the treatment of psoriasis in Chinese population.
Design and methods  This was an open-label, single-arm, multicentre pilot study conducted at three centres. Patients with a body surface area ≥ 10% and psoriasis area and severity Index (PASI) ≥ 12 were given 15 mg alefacept intramuscularly once a week for 12 weeks and were then followed up for a further 12 weeks.
Results  A total of 46 patients was enrolled. Only one subject (2%) achieved a ≥ 75% improvement in PASI at week 14. The median improvement in PASI at week 14 after the 12-week treatment was 39%. At any time during the 6-month course, 3 subjects (7%) achieved a Physician Global Assessment (PGA) of 'almost clear', and a ≥ 50% and ≥ 75% improvement in PASI was seen in 46% and 9%, respectively. There is a trend for decreased counts of CD4⁺ and CD8⁺ cells after alefacept treatment, but subjects who achieved PASI50 showed a lesser degree of decrease in CD4⁺ and CD8⁺ counts compared with those in patients who did not achieve PASI50.
Conclusions  This small pilot study indicated that intramuscular alefacept was effective and safe in psoriasis in Chinese patients over 12 weeks of treatment. Further studies are needed to clarify the reason for low PASI 75 effectiveness and the paradoxical lesser decline of CD4⁺ and CD8⁺ T cells in those who responded.     

Mycosis fungoides skin lesions contain CD8+ tumor-infiltrating lymphocytes expressing an activated, MHC-restricted cytotoxic T-lymphocyte phenotype

In prior studies, we showed that most CD8⁺ cells infiltrating skin lesions of CD3⁺CD4⁺ mycosis fungoides were CD3⁺ T-line-age tumor-infiltrating lymphocytes (TIL) whose overall phenotype was suggestive of MHC-restricted cytotoxic T lymphocytes (CTL). However, their lack of cytotoxic-associated granzyme A mRNA suggested that they might be inactivated CTL precursors. In this study, we used single- and double-label immunohistologic techniques to assess the expression of TlA-1-reactive protein and HLA-DR by these CD8⁺TIL. Monoclonal antibody TIA-1 recognises a novel family of proteins expressed preferentially by cytotoxic cells, including some that lack grauzyme A. HLA-DR is a marker of T-cell activation. Single-label studies of 32 cases showed that CD8⁺TIL and TIA-1⁺ cells constituted a variable minority of the total cellular infiltrate and had a similar distribution. Double-label studies of 14 cases showed that in most instances the aggregate phenotype of the majority of CD8⁺TIL was CD3⁺TIA-1⁺HLA-DR⁺CD56⁻CD57⁻. These findings suggest that many of the CD8⁺TIL within skin lesions of CD3⁺CD4⁺ mycosis fungoides are activated, MHC-restricted CTL.     

A clinico-pathological study of 70 cases of pemphigus

A clinicopalhological study of 70 cases of pemphigus observed over a span of four and a half years from January 1992 to June 1996 at the Sir J.J. Group of Hospitals and Grant Medical College, Mumbai is reported. Pemphigus vulgaris constituted the single largest group of 43 cases, followed by pemphigus foliaceus (25 cases) and pemphigus vegetans (2 cases). Majority of the cases were seen in the age group of 21-60 years, with a slight male predominance. The youngest patient was 14 years while the eldest was aged 75 years. Mucosal involvement was seen in 31 cases of pemphigus vulgaris, as opposed to only 5 cases of pemphigus foliaceus. Flaccid bullae were present in 100% cases. Pruritus was complained of in 14 cases, though it was more common in pemphigus vegetans and vulgaris. Salient histopathological features of pemphigus vulgaris observed were (I) intraepidermal suprabasal blisters (35 cases), (2) presence of acantholytic cells (40 cases), (3) "Row of tombstone appearance" (I8 cases) and (4) acantholysis involving follicular sheath (20 cases). Main histopathological features of pemphigus foliaceus were (1) subcorneal blister (15 case), (2) acantholysis (24 cases) and (3) bulla cavity containing inflammatory infiltrate (12 cases). Both cases of pemphigus vegetans showed hyperkeratosis, papillomatosis and irregular acanthosis with intra-epidermal eosinophilic abscesses besides suprabasal lacunae.     

In vivo depletion of CD8+ T cells restores hair growth in the DEBR model for alopecia areata

Summary Alopecia areata (AA) is a putative autoimmune disease in which anagen hair follicles are the target of immune cell attack. While both CD4⁺ and CD8⁺ T lymphocytes are prominent in the infiltrate, their respective roles in the pathogenesis of AA remain unknown. Here we directly investigated the activity of CD8⁺ cells in the inhibition of hair growth using the Dundee experimental bald rat (DEBR) model for AA. Eight lesional DEBRs were fully depleted of their CD8⁺ cells by intraperitoneal injection of OX-8 monoclonal antibody (MoAb) specific for these cells over a 15-day therapy course. A control group of eight lesional rats was injected with the irrelevant MoAb OX-21. Sequential blood samples were analysed by flow cytometry to observe changes in the CD8⁺ cell population and macropliotography used to record changes in hair growth activity.
All eight CD8⁺ depleted rats started to regrow hair within 29 days from the start of treatment, the tinal response ranging from sparse regrowth to a near normal coal. While two rats maintained their new pelage, the remainder lost hair as the CD8⁺ population in peripheral blood increased. Two of the control rats also showed hair regrowth over the experimental period of 156 days. These results suggest that CD8⁺ cells play an active part in the pathogenesis of AA. As hair production did not fully recover in all animals, immune mechanisms other than CD8⁺ cells may be involved in effecting hair loss. However, analysis of CD8⁺ cell levels in the skin of CD8⁺ depleted rats may help resolve their full importance in AA.     

Molecular mechanisms of pathogenesis

The first clue to the etiology of pemphigus was established in 1964, when Beutner and Jordon¹ demonstrated that serum from pemphigus patients contained autoantibodies that bound to an intercellular substance (ICS) of skin and mucosa. Subsequently, skin biopsies revealed in vivo deposition of auto-antibodies in the epidermis of pemphigus patients.² While these results were intriguing, they did not prove that antibody played a role in the acantholytic process. The following three lines of evidence do support a role for antibody in the induction of acantholysis in pemphigus: correlation of antibody titers with disease activity^3,4; induction of acantholytic lesions in the skin of neonatal mice⁵ or in grafts of human oral mucosa on nude mice⁶ following passive transfer of patient IgG; and induction of acantholytic lesions in expiants of normal human skin following incubation with patient IgG.^7,8 The first two lines of evidence have been discussed in other chapters of this volume. It is our intention to describe experimental results from several laboratories confirming the pathologic events induced in normal human skin by serum or IgG preparations from pemphigus patients and to discuss the molecular events leading to the pathophysiology of pemphigus.     

Simultaneous occurrence of herpetiform pemphigus and endemic pemphigus foliaceus (fogo selvagem)

A 32–year-old woman from Franco da Rocha, one of the last endemic areas of pemphigus foliaceus (fogo selvagem, FS) in the state of Sao Paulo, Brazil,'² developed generalized FS based on clinical (see Fig. 1), histologic and immunologic criteria.³ She had subcorneal vesicles with acantholytic cells histologically, circulating intercellular immunoglobulin G (IgG) autoantibodies at a titer of 640, and deposits of IgG in epidermal intercellular spaces. Her sister also had FS. The course of the disease was chronic with periods of remission and relapses. Six years later, she developed pruritic erythematous edematous plaques with overlying vesicles and blisters in a herpetiform pattern on the abdomen and forearm (Fig. 2) that resembled lesions of dermatitis herpetiformis. The lesions disappeared with prednisone 40 mg/day. Five years later, while affected with typical lesions of FS, she developed intensely pruritic erythematous urticarial edematous plaques (Fig. 3), some of which were covered with vesicles typical of herpetiform pemphigus (HP) (Fig. 4). Histologically these lesions showed epidermal spongiosis, with eosinophilic exocytosis and acantholysis (Fig. 5). Direct immunofluorescence (DIF) was positive for granular intercellular deposits of IgG and C3 in the epidermis (Fig. 6). IgA Studies were negative. Circulating Intercellular IgG autoantibodies were present at a titer of 80. By immunoblotting, the sera reacted to a 160 kD antigen which co-migrated with desmoglein–1 detected by monoclonal antibody (AE 23) (kindly provided by Dr. Tung-Tien Sun, New York University Medical Center, New York) and by pemphigus foliaceus sera (Fig. 7). Thus, after 12 years of FS, the patient developed a mixed bullous disease with concomitant clinical and laboratory features typical of HP and FS.     

Elastic fiber pattern in scleroderma/morphea

Background: Scleroderma/morphea is characterized by expansion of the dermis with thickened collagen bundles and loss of CD34⁺ dermal dendrocytes. Variable elastic fiber changes have been described, but to our knowledge, no systematic study of the elastic fiber pattern correlated with CD34 expression has been reported.
Methods: To better define the typical elastic fiber morphology, we examined seven cases of normal skin and 28 cases of scleroderma/morphea ranging from inflammatory to sclerosing stages. All but four biopsies were submitted with a clinical impression of either scleroderma or morphea. CD34 immunohistochemistry was performed on 26 biopsies with available tissue.
Results: Elastic van Gieson stain showed preservation of elastic fibers in all cases. In addition, straightening with parallel orientation and compression between thickened collagen bundles was frequently present and was graded as limited in 46% and diffuse in 54% of cases. The extent of elastic fiber alteration correlated with the degree of sclerosis. A variable loss of CD34⁺ dermal dendritic cells was seen in all cases.
Conclusion: This study confirms the preservation and frequent presence of parallel, straightened and compressed elastic fibers in scleroderma/morphea and suggests that the elastic fiber pattern, in addition to CD34 immunohistochemistry, may serve as a useful diagnostic adjunct.     

CD30+ lymphoproliferative disorders: histopathology, differential diagnosis, new variants, and simulators

Summary:  CD30⁺ lymphoproliferative disorders of the skin (CD30⁺ LPD) represent a well-defined spectrum of primary cutaneous T-cell lymphomas which have been recognized as distinct entities in recent lymphoma classifications. Lymphomatoid papulosis and anaplastic large-cell lymphoma share the expression of CD30 antigen as a common phenotypic hallmark but differ in regard to their clinical and histologic features as well as their biologic behavior. This article summarizes the histologic features of CD30⁺ LPD and presents recently identified new clinicopathologic variants of CD30⁺ LPD. There is an increasing number of reactive inflammatory disorders and neoplastic diseases which are composed of or contain a significant number of CD30⁺ cells and mimic LyP or anaplastic large cell lymphoma clinically or histologically. Differential diagnostic considerations focus on other lymphoproliferative processes with CD30⁺ tumor cells as well as non-lymphoid neoplasms and inflammatory simulators. The term CD30⁺ pseudolymphoma is proposed to designate inflammatory processes with CD30⁺ T cells. The final diagnosis of CD30⁺ LPD is based on a synthesis of clinical, histologic, phenotypic, and molecular genetic findings.     

Characterization of lymphocytic infiltrate cells in bullous pemphigoid and pemphigus vulgaris

By means of monoclonal antibodies (mab) and alkaline phosphatase anti-alkaline-phosphatase (APAAP) technique, the distribution and characteristics of lymphocytic infiltrates were studied in biopsies from 15 patients with bullous pemphigoid (b.P.) and 5 patients with pemphigus vulgaris (P.v.). The biopsies were obtained from freshly developed blisters along with perilesional tissue. The lymphocytic infiltrates in b.P. as well as in P.v. were located in the area of the fresh lesions and consisted almost exclusively of T cells (CD3 positive lymphocytes). In b.P., the discrepancy between a decreased number of CD2 positive lymphocytes (10-20%) and markedly higher number of CD3 staining cells (50-60% of all infiltrate cells) was striking. The characterization of the T cell subpopulations in both dermatoses showed mainly T helper cell infiltrates (CD4), while only up to 10% of T suppressor cells (CD8) were detected. CD45R positive (CD4+/CD45R+: suppression inducing) as well as CD29-positive (CD4+CD29+: cells which provide help for antibody production) T-cell subpopulations were detected in both dermatoses particularly adjacent to blister in up to 10% of the cell infiltrates. Epidermal staining with CD29 mab in b.P. up to the stratum spinosum and in P.v. within intraepidermal blisters was detected. By means of CD19 and CD21 mab B lymphocytes were minimal. Perivascular individual cell staining occurred with CD7 CD16, CD56 and CD57 mab (K/NK cells) in b.P. as well as in P.v. patients. The predominance in T cell infiltrates, particularly T helper cells, suggests the role of cellular immune mechanism in the pathogenesis of these diseases, in b.P. the CD2 antigen (SE receptor) appears to be of particular importance.     

Different patterns of in vitro acantholysis in normal human skin samples explanted from different sites of the body

Background The factors that contribute to a preferential anatomic localization of pemphigus lesions are not well known. In particular, the question arises as to whether certain skin areas may be more acantholysis-prone than others.
Objective To verify whether, in pemphigus patients, a different susceptibility to acantholysis exists among different cutaneous regions, the technique of tissue cultures was used.
Methods Normal human skin explants from two distinct anatomic regions (back and buttocks) of two former pemphigus patients were cultured in vitro in the presence of enalapril (6 mM) or cystamine (10 mM), two substances with a proven biochemical acantholytic effect. After 4 days of culture, the tissues were processed for standard histology.
Results Diffuse acantholysis, with large intraepidermal splits, was observed in the explants taken from the backs of both subjects and cultured with either enalapril or cystamine. Mild to moderate acantholytic changes were detected in the explants taken from the buttocks of both subjects and cultured with either enalapril or cystamine. No structural changes were seen in the control cultures.
Conclusions Pemphigus patients present different thresholds of acantholysis in different areas of their bodies. This might explain, at least in part, certain preferential anatomic localizations of pemphigus lesions.     

Clinical-scale generation of strongly CD83-expressing dendritic cells using extracorporeal photopheresis

Background: Many strategies are currently being pursued in order to generate mature dendritic cells (DC) to be used for immunotherapy. A potent anti-tumour influence by extracorporeal photopheresis has been documented for cutaneous T-cell lymphoma, and a major mechanism of action has been suggested to be generation of DC presenting tumour antigens.
Purpose: To determine the potential of a simple clinical photopheresis protocol for large-scale development of mature DC.
Methods: A standard monocyte-enriched leukapheresis preparation of 10⁹–10¹⁰ cells was derived during each of five consecutive treatment sessions of a patient with cutaneous T-cell lymphoma. The cells were incubated overnight in autologous plasma with no addition of growth medium. Cell surface lymphocyte, monocyte and DC markers were determined using multi-colour flow cytometry.
Results: We find signs of activation of the CD14+ monocytes, as well as the appearance of a minor population of mature DC negative for CD14 but with strong CD83 expression.
Conclusions: With a procedure appropriate for routine clinical use, a total number of 10⁶–10⁷ DC ready for patient reinfusion can be prepared within 24 h. Our findings indicate the need to further explore the capacity of photopheresis to stimulate cancer patients' anti-tumour defence reaction.     

Immunological assessment of familial tinea corporis

Background  The mechanisms involved in the immune resistance to fungal infection of the skin are not well understood. We assessed the levels of the various lymphocyte subsets, the HLA haplotypes, the expression of various receptors on natural killer (NK) cells and the serum levels of cytokines, in a family in which four siblings had tinea corporis, while four others were healthy, in order to reveal potential factors of susceptibility to dermatophytes.
Observations  Normal numbers of T, B and NK cells were found in the peripheral blood, without significant differences between healthy and infected siblings. The frequency of CD14-positive monocytes was elevated in infected compared with healthy siblings. The proportion of NKG2A⁺ NK cells was reduced in the patients compared with healthy siblings (23.8% vs. 33.8%), whereas CXCR3⁺ NK cells were increased (41.5% vs. 25.6%, respectively). MHC class I and class II haplotypes were disease independent. Elevated levels of intereron-γ, interleukin-8 (IL-8), IL-2 and tumour necrosis factor-α (TNFα) were observed only in part of the infected siblings. The serum level of TNFα was strongly correlated with the percentage of CD14⁺ monocytes.
Conclusions  We studied here in detail the NK functions of a family of patients suffering from tinea corporis and observed skewed frequencies of specific NK receptors, which imply possible involvement of NK cells in susceptibility to fungal infection.     

Detection of epidermodysplasia verruciformis-like human papillomavirus types in malignant and premalignant skin lesions of renal transplant recipients

Summary A 76-year-old man presented with a 3-month history of a cutaneous nodute on the right thigh. The tumour was composed of CD3⁺, large atypical cells, and CD20⁺, small normal-appearing cells. Flow cytometry showed that CD20⁺ cells outnumbered CD3⁺ cells. By Southern blot hybridization analyses, the malignant cells were shown to be of T-cell origin, because of the presence of rearranged bands for the β chain of the T-cell receptor, but not for the immunoglobulin heavy chain. This case represents a T-cell lymphoma intermingled with a large number of non-neoplastic B cells.     

Adhesion molecules and related proteins in Darier''s disease and Hailey–Hailey disease

We have used antibodies to plakoglobin and E-cadherin: the lectins, peanut agglutinin (PNA) and soybean agglutinin (SBA); and sera from patients with the autoimmune diseases pemphigus vulgaris (PV) or pemphigus foliaceus (PF), in an immunohistological study of Darier's disease and Hailey-Hailey disease. There was normal expression of plakoglobin, E-cadherin, lectins and pemphigus antigens at the periphery of keratinocytes in uninvolved skin. Clumps of plakoglobin were detected within acantholytic cells in Hailey-Hailey disease, whereas expression was diffuse in acantholytic cells in Darier's disease. This difference may reflect differences in the pathogenesis of acantholysis. E-cadherin expression was weak or absent at the periphery of some acantholytic cells; lectin binding was sometimes reduced around acantholytic cells, and pemphigus antibodies did not bind to the acantholytic cells involved skin in either disease. Internalization, conformational changes or proteolysis may alter the expression of extracellular epitopes by acantholytic cells.     

卡介菌多糖核酸联合中药对白癜风患者T细胞亚群及Fas/FasL系统表达的调节

【摘要】 目的 探讨卡介菌多糖核酸（BCG-PSN）联合中药白癜风颗粒治疗白癜风临床疗效及对免疫的调节作用。 方法 流式细胞仪和ELISA法检测BCG-PSN联合白癜风颗粒治疗白癜风前后T细胞亚群及外周血淋巴细胞Fas及FasL的表达水平,并与BCG-PSN及白癜风颗粒单一治疗对照组进行比较。结果 BCG-PSN联合白癜风颗粒治疗组总有效率达82.86%,明显高于BCG-PSN对照组的40.63%（P ＜ 0.01）。各组治疗前外周血CD3+、CD3+CD4+、CD3+CD8+均低于健康对照组（P ＜ 0.01）, CD4+/CD8+比值升高（P ＜ 0.01）, Fas表达明显降低（P ＜ 0.01）。治疗后CD3+、CD3+CD4+、CD3+CD8+较治疗前升高 （P ＜ 0.05）,CD4+/CD8+比值下降（P ＜ 0.05）,Fas明显上升（P ＜ 0.01）。结论 BCG-PSN可通过逆转外周血淋巴细胞的Fas/FasL表达异常,诱导淋巴细胞的正常凋亡,与中药合用起协同作用。     

Resistance to activation-induced cell death and bystander cytotoxicity via the Fas/Fas ligand pathway are implicated in the pathogenesis of cutaneous T cell lymphomas

By engaging Fas, Fas ligand (FasL) on activated T lymphocytes induces activation-induced cell death (AICD), and also triggers apoptosis of target cells during immune downregulation. We previously showed that within cutaneous T cell lymphoma (CTCL) lesions, malignant CD4(+) T cells expressing FasL accumulated, and were inversely distributed with CD8(+) T cells. We thus determined the responses of human CTCL cells to AICD and their cytotoxic to Fas(+) target T cells in vitro. CTCL cells expressing Fas were resistant to AICD following activation by CD3 monoclonal antibody (mAb) whereas still undergoing apoptosis if Fas was ligated to Fas mAb. CTCL cell lines, as well as Sezary Syndrome patients' peripheral blood lymphocytes, exhibited ratio-dependent cytotoxicity to Fas(+) Jurkat cells. The kinetic study showed that FasL surface expression was absent before activation, and its expression was low and/or delayed after activation. We therefore hypothesize that CTCL cells express functional FasL possibly contributing to bystander cytotoxicity within tumor infiltrates. In addition, decreased and/or delayed FasL surface expression following activation may in part contribute to their resistance to AICD. Both bystander cytotoxicity and resistance to AICD are likely to contribute to the loss of cytotoxic anti-tumor CD8(+) T cells as well as the accumulation of malignant T cells in CTCL.     

Possible role of Fas/Fas ligand-mediated apoptosis in the pathogenesis of fixed drug eruption

BACKGROUND: Although epidermal and dermal T cells play roles in the pathogenesis of fixed drug eruption (FDE), not much is known about keratinocyte death and its precise mechanism in FDE. OBJECTIVES: Our aim is to elucidate the mechanism that underlies keratinocyte death in FDE, that is, the role of apoptosis and its signalling pathway. METHODS: We first examined the involvement of apoptosis in the active FDE lesions by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labelling (TUNEL) assay and immunohistochemical analysis of caspase-3. We then examined the expressions of Fas and Fas ligand (FasL) to deduce the possible upstream signalling pathway of apoptosis, if apoptosis were involved. We finally characterized the infiltrated T-cell subpopulations in the active FDE lesions. RESULTS: In the active FDE lesions, TUNEL positivity was strongly observed in the basal keratinocytes, and also weakly observed in the upper dermal infiltrates as well as in a few keratinocytes in the granular layer. The distribution of TUNEL-positive cells was similar to that of the strong staining of active capase-3. Fas was found mainly in the keratinocytes and some infiltrated dermal cells, whereas FasL was identified predominantly in the intraepidermal and dermal infiltrated cells and in some basal keratinocytes. Overlapping expression of Fas and FasL was accompanied by apoptosis in the FDE lesions. Many of the infiltrated mononuclear cells were CD8+. Perforin was rarely observed in the FDE lesions. CONCLUSIONS: These findings suggest that apoptosis of the keratinocyte is highly likely to be involved in the pathogenesis of FDE, and this cytotoxicity might be predominantly mediated by the FasL of the infiltrating CD8+ T cells, possibly also playing an inflammatory role.