Seawater induces apoptosis in alveolar epithelial cells via the Fas/FasL-mediated pathway

Our previous study showed that seawater can cause lung tissue cell apoptosis; in the present study, the immunohistochemistry and Western blot analysis results demonstrated that Fas, FasL, and cleaved caspase-8 and caspase-3 were up-regulated in the rat lungs exposed to seawater. We found that seawater-induced human lung alveolar epithelial A549 cell apoptosis was concentration and time dependent. Moreover, seawater increased the expression of Fas, FasL, and cleaved caspase-8 and caspase-3 in A549 cells. The incubation of A549 cells in the presence of FasL-neutralising antibody (NOK-2) or caspase-8 inhibitor (Z-IETD-FMK) resulted in a decrease of seawater-induced cell apoptosis. NOK-2 inhibited Fas/FasL interaction and reduced the cleavage of caspase-8 and caspase-3, and Z-IETD-FMK blocked caspase-8 and caspase-3 activation. Seawater similarly produced a significant increase in rat alveolar type II cell apoptosis and expression of Fas and cleaved caspase-8. In summary, the Fas/FasL pathway involved in alveolar epithelial cell (AEC) apoptosis could be important in the pathogenesis of seawater-induced acute lung injury (SW-ALI).     

Activated T killer cells induce apoptosis in lung epithelial cells and the release of pro-inflammatory cytokine TNF-alpha

Apoptosis is thought to be involved in lung epithelial cell damage in acute respiratory distress syndrome and interstitial pneumonia. Both the role of apoptosis and its underlying molecular mechanisms in human lung tissue remain unclear. To address these issues, we developed an in vitro assay in which a human lung epithelial cell line and a staphylococcal enterotoxin B (SEB)-reactive human CD8(+) CTL line were co-cultured in the presence of SEB. SEB-stimulated CD8(+) CTL induced apoptosis in the lung epithelial cell line primarily through the perforin/granzyme-mediated pathway. In these cells, apoptosis was initially independent of death receptor pathways. We also tested the effect of IFN-gamma on modulation of apoptosis in lung epithelial cells. In IFN-gamma-pretreated lung epithelial cells, CD95 (APO-1/Fas) activation as well as TNF-related apoptosis-inducing ligand (TRAIL) receptor and TNFR activation led to apoptosis. Furthermore, we found that the interaction of SEB-stimulated CD8(+) CTL with lung epithelial cells induced an increase in TNF-alpha secretion. These results suggest an important role for bacterial superantigen-reactive CD8(+) CTL in induction of lung epithelial cell apoptosis and in modulation of inflammatory processes in lung tissue.     

Soluble egg antigen-stimulated T helper lymphocyte apoptosis and evidence for cell death mediated by FasL(+) T and B cells during murine Schistosoma mansoni infection

Granuloma formation around schistosomal eggs is induced by soluble egg antigens (SEA) and mediated by the activity of CD4(+) Th lymphocytes and their cytokines. Regulation of the inflammatory Th cell response during infection is still insufficiently understood. The hypothesis of this study was that activation-induced cell death (AICD) of CD4(+) T cells is involved in the immune inflammatory response. This study investigated the dynamics of splenic and granuloma CD4(+) Th cell apoptosis and Fas ligand (FasL) expression during the acute and chronic stages of murine schistosomal infection. Enhanced apoptosis of freshly isolated CD4(+) Th lymphocytes commenced after egg deposition and persisted during the peak and modulated phases of granuloma formation. After oviposition, CD4(+), CD8(+), and CD19(+) splenocytes and granuloma cells expressed elevated levels of FasL but FasL expression declined during the downmodulated stage of infection. In culture, SEA induced splenic and granuloma CD4(+) T-cell apoptosis and stimulated expression of FasL on splenic but not granuloma CD4(+) T cells, CD8(+) T cells, and CD19(+) B cells. SEA-stimulated splenocytes and granuloma cells preferentially lysed a Fas-transfected target cell line. Depletion of B cells from SEA-stimulated splenic cultures decreased CD4(+) T cell apoptosis. Coculture of purified splenic B cells with CD4(+) T cells and adoptive transfer of purified B cells indicated that antigen-stimulated B cells can kill CD4(+) Th cells. However, CD4(+) T cells were the dominant mediators of apoptosis in the granuloma. This study indicates that AICD is involved in the apoptosis of CD4(+) T cells during schistosomal infection.     

Induction of interleukin-8 secretion and apoptosis in bronchiolar epithelial cells by Fas ligation.

Epithelial cell injury is the common manifestation of lung injury. Contributing to such injury of epithelial cells is apoptosis. Although apoptosis is part of the normal process of epithelial renewal, in excess it is pathologic. We previously demonstrated the excessive apoptosis of lung epithelial cells and the upregulation of Fas and Fas ligand (FasL) in fibrosing lung diseases. We also showed that inhalation of anti-Fas antibody induced lung injury and fibrosis in mice. Interleukin (IL)-8 is one of the most important cytokines in the pathophysiology of acute lung injury and pulmonary fibrosis. In this study we investigated whether Fas ligation induces IL-8 secretion in addition to apoptosis in bronchiolar epithelial cells in vitro. Bronchiolar epithelial cells underwent apoptosis and also secreted IL-8 in response to tumor necrosis factor (TNF)-alpha or Fas ligation. New gene expression and protein synthesis were not necessary for Fas ligation- and TNF-alpha- mediated apoptosis, but were necessary for IL-8 secretion. We further found that Fas ligation induced activation of nuclear factor-kappa B. We conclude that the Fas/FasL pathway not only mediates apoptosis but also plays a proinflammatory role, and that stimulation of the Fas/FasL pathway in bronchiolar epithelial cells leads to IL-8 production, which may amplify the inflammatory cascade in lung injury and pulmonary fibrosis.     

The role of apoptosis in the pathophysiology of Acute Respiratory Distress Syndrome (ARDS): An up-to-date cell-specific review

ARDS pathophysiology is characterized by complex mechanisms that involve cells of inflammation, lung tissue cells, cytokines, chemokines, as well as apoptosis activators and inhibitors. There are two important theories that link apoptosis with ARDS and suggest that epithelial cell apoptosis, as well as the accumulation of neutrophils in the lung, may contribute to a cascade of events and, finally, ARDS. The activation of the Fas/FasL pathway is an important mechanism of alveolar epithelial injury in the lungs of patients with ALI. In addition, neutrophilic inflammation in the alveolar spaces is characteristic of ALI in humans and in most animal models of ALI. The enhanced phagocytosis of apoptotic neutrophils could lead to resolution of inflammation and repair during ARDS. In this review, we will focus on elucidating the role of apoptosis in the pathophysiology of ARDS and the contribution of Fas-mediated inflammation in ARDS. Furthermore, we will give evidence that TNF-alpha, IL-1beta and IL-13 attenuate the pro-cell death effects of Fas/CD95 on A549 epithelial cells, at least partially, by the NF-kB and PI3-K pathways, suggesting that induction of the expression of antiapoptotic genes protects the epithelial cells from cell death.     

Requirement for tumor necrosis factor-receptor 2 in alveolar chemokine expression depends upon the form of the ligand

Respiratory virus infection evokes a potent T-cell response that may result in a considerable insult to the structural and functional integrity of the gas exchange units of the lung. Alveolar antigen recognition by CD8+ T lymphocytes results in significant injury that is critically dependent upon tumor necrosis factor (TNF)-alpha expressed by the CD8+ T cells and is largely dependent upon TNF-receptor 1 expression on the alveolar epithelial target cells. TNF-receptor 2 (TNF-R2)-deficient mice were used to demonstrate that CD8+ T-cell-mediated lung injury associated with clearance of experimental influenza requires TNF-R2 for full expression of immunopathology. In vitro analysis indicates that alveolar cell expression of TNF-R2 is critical in the induction of epithelial monocyte chemoattractant protein (MCP)-1 expression specifically in response to soluble TNF-alpha, suggesting an important role for this receptor in bystander lung injury. However, TNF-R2 was dispensable for induction of alveolar MCP-1 expression in response to transmembrane TNF-alpha expressed by antigen-specific CD8+ T cells, and the effects of the two receptors seem to be additive. Because TNF-R2 may be rapidly shed as part of feedback inhibition of bystander inflammation, this suggests a mechanism by which immunopathology in respiratory virus infection may be regulated and by which T-cell receptor-dependent TNF-alpha activity might bypass such negative regulation for contact-dependent antiviral activities.     

Fas/FasL and perforin/granzyme pathway in acute rejection and diffuse alveolar damage after allogeneic lung transplantation—a human biopsy study

Acute rejection and diffuse alveolar damage are major problems during the early time after transplantation. Against this background, lung biopsies after allogeneic lung transplantation were studied using immunohistochemistry. Biopsies with acute rejection, diffuse alveolar damage and morphological inconspicuous biopsies were chosen. The objectives of this study were to ascertain: (a) if and how CD4 and CD8 T cells contribute to allograft rejection and diffuse alveolar damage, (b) whether there is a correlation of the chemoattractant regulated on activation normal T cells (RANTES) with the mononuclear infiltrate and (c) whether perforin/granzyme and Fas/FasL pathways contribute to lung injury after lung transplantation. Our results show that CD4⁺ and CD8⁺ T cells were increased in biopsies with acute rejection and, to a minor extent, also in biopsies with diffuse alveolar damage due to reperfusion injury. RANTES expression of T cells was increased in biopsies with acute rejection. Perforin seemed to have a dual role in the alloimmune response. In one regard, it had a cytolytic function in the acute rejection process, and, in contrast, it may be responsible for downregulating both CD4- and CD8-mediated alloimmune responses. The FasL/Fas pathway is not only important for induction of apoptosis during rejection but is also a mechanism of lung injury in the development of diffuse alveolar damage.     

Changes in sensitivity of peripheral lymphocytes of autoimmune gld mice to FasL-mediated apoptosis reveal a mechanism for the preferential deletion of CD4-CD8-B220+ T cells

During thymic selection 'mis-selected' CD8(+) T cells exit to the periphery where they are deleted by a Fas/FasL-mediated mechanism, presumably as a result of activation by self-antigens. In the absence of functional FasL, as is the case in autoimmune gld mice, these 'mis-selected' T cells develop into unique Thy1(+)CD4(-)CD8(-) TCRalphabeta(+)B220(+) lymphocytes [abnormal double negative T (DN T) cells]. Using bioactive FasL-bearing vesicles [FasL vesicle preparation (FasL VP)], we were able to induce acute apoptosis in freshly isolated lymphocytes and to demonstrate that peripheral lymphocytes of gld mice become more sensitive to the FasL-mediated apoptosis as they age. Furthermore, flow cytometric analyses indicated that within this peripheral lymphocyte population, the abnormal DN T cells were preferentially eliminated. The exquisite sensitivity of these abnormal DN T cells is attributed to their increased membrane Fas expression with a concomitant reduction of cytosolic FLIP(L). Our data support the hypothesis that specific components of the Fas-mediated apoptotic pathway are modulated in favor of the elimination of auto-reactive T cells as well as those CD8(+) T cells that are 'mis-selected' in the thymus and escape to the periphery.     

CD8+ T cells promote inflammation and apoptosis in the liver after sepsis: role of Fas-FasL

Although studies blocking the Fas pathway indicate it can decrease organ damage while improving septic (cecal ligation and puncture, CLP) mouse survival, little is known about how Fas-Fas ligand (FasL) interactions mediate this protection at the tissue level. Here, we report that although Fas expression on splenocytes and hepatocytes is up-regulated by CLP and is inhibited by in vivo short interfering RNA, FasL as well as the frequency of CD8(+) T cells are differentially altered by sepsis in the spleen (no change in FasL, decreased percentage of CD8(+) and CD4(+) T cells) versus the liver (increased FasL expression on CD8(+) T cells and increase in percentage/number). Adoptive transfer of CLP FasL(+/+) versus FasL(-/-) mouse liver CD8(+) T cells to severe combined immunodeficient or RAG1(-/-) recipient mice indicated that these cells could induce inflammation. The FasL-mediated cytotoxic capacity of these septic mouse liver CD8(+) T cells was shown by their ability to damage directly cultured hepatocytes. Finally, although CD8(-/-) mice exhibited a reduction in both CLP-induced liver active caspase-3 staining and blood interleukin-6 levels, only FasL(-/-) (but not CD8(-/-)) protected the septic mouse spleen from increasing apoptosis. Thus, although truncating Fas-FasL signaling ameliorates many untoward effects of sepsis, the pathological mode of action is distinct at the tissue level.     

Expression of FasL and Fas protein and their soluble form in patients with hypersensitivity pneumonitis

BACKGROUND: Hypersensitivity pneumonitis (HP) is characterized by a lymphocytic alveolitis and loosely formed granulomas in lung biopsy specimens. HP improves or disappears altogether after cessation of antigen exposure. The Fas-Fas ligand (FasL) system is one of the representative systems of apoptosis-signaling receptor molecules, and is involved in various inflammatory diseases. We hypothesized that the Fas-FasL system may be associated with this disorder. METHODS: We examined the expression of FasL and Fas proteins in lung tissues from patients with HP using immunohistochemistry. We also measured the soluble form of FasL (sFasL) and sFas levels in serum and bronchoalveolar lavage fluid (BALF) from patients with HP using enzyme-linked immunosorbent assay (ELISA). Furthermore, we also measured the cytotoxic activity of BALF sFasL in vitro. RESULTS: FasL was detected in infiltrating mononuclear cells, and Fas was detected in infiltrating mononuclear cells, alveolar macrophages, and epithelioid cells in HP, whereas FasL was not detected and Fas was detected in few alveolar macrophages in controls. The levels of sFasL and sFas in BALF, but not in serum, were significantly increased in HP compared with controls. BALF of HP that included high levels of sFasL had no cytotoxic activity for bronchiolar epithelial cells in vitro. CONCLUSIONS: In HP, there is an upregulation of FasL and Fas in lung tissues. Since there is no incidence of apoptosis and no cytotoxic activity for lung epithelial cells in BALF from patients with HP, the increased levels of BALF sFasL and sFas may reflect the activation and sequestration of inflammatory cells rather than apoptosis.     

Enhanced T cell apoptosis in common variable immunodeficiency: negative role of the fas/fasligand system and of the Bcl-2 family proteins and possible role of TNF-RS

CVI is a primary immunodeficiency characterized by a failure of B cell differentiation associated with an array of T cell defects, such as enhanced T cell apoptosis. In this study we investigated the mechanisms underlying CVI enhanced T cell death. We analysed both the expression of Fas using flow cytometry techniques and the expression of FasL mRNA using RT-PCR in CVI T cells. We could not find any significant differences between CVI and normal subjects with regard to Fas expression, although there was a subgroup of CVI patients with very high Fas expression which was accompanied by an up-regulation of FasL mRNA. However, attempts to induce Fas-mediated apoptosis in these high Fas expressing cells, as evaluated by propidium iodide staining and APO2.7 staining, were unsuccessful. We also investigated intracellular levels of Bcl-2, bcl-xl and bax in CD4(+) and CD8(+) CVI T cells, as well as the bax/Bcl-2 ratio, using flow cytometry techniques but could not detect any differences between CVI and normal subjects. Finally we analysed TNF-RI and TNF-RII mRNA expression in CD4(+) and CD8(+) CVI T cells using semiquantitative RT-PCR and found a significant increase in expression of both TNF-Rs in CD4(+) T cells from CVI patients. Our data suggest that the increased expression of both TNF-Rs on T cells may be one of the mechanisms responsible for the accelerated T cell apoptosis in CVI.     

Fas (CD95) induces alveolar epithelial cell apoptosis in vivo: implications for acute pulmonary inflammation

Activation of the Fas/FasL system induces apoptosis of susceptible cells, but may also lead to nuclear factor kappaB activation. Our goal was to determine whether local Fas activation produces acute lung injury by inducing alveolar epithelial cell apoptosis and by generating local inflammatory responses. Normal mice (C57BL/6) and mice deficient in Fas (lpr) were treated by intranasal instillation of the Fas-activating monoclonal antibody (mAb) Jo2 or an irrelevant control mAb, and studied 6 or 24 hours later using bronchoalveolar lavage (BAL), histopathology, DNA nick-end-labeling assays, and electron microscopy. Normal mice treated with mAb Jo2 had significant increases in BAL protein at 6 hours, and BAL neutrophils at 24 hours, as compared to lpr mice and to mice treated with the irrelevant mAb. Neutrophil recruitment was preceded by increased mRNA expression for tumor necrosis factor-alpha, macrophage inflammatory protein-1alpha, macrophage inflammatory protein-2, macrophage chemotactic protein-1, and interleukin-6, but not interferon-gamma, transforming growth factor-ss, RANTES, eotaxin, or IP-10. Lung sections from Jo2-treated normal mice showed neutrophilic infiltrates, alveolar septal thickening, hemorrhage, and terminal dUTP nick-end-labeling-positive cells in the alveolar septae and airspaces. Type II pneumocyte apoptosis was confirmed by electron microscopy. Fas activation in vivo results in acute alveolar epithelial injury and lung inflammation, and may be important in the pathogenesis of acute lung injury.     

Alveolar epithelial cell therapy with human cord blood-derived hematopoietic progenitor cells

The role of umbilical cord blood (CB)-derived stem cell therapy in neonatal lung injury remains undetermined. We investigated the capacity of human CB-derived CD34(+) hematopoietic progenitor cells to regenerate injured alveolar epithelium in newborn mice. Double-transgenic mice with doxycycline (Dox)-dependent lung-specific Fas ligand (FasL) overexpression, treated with Dox between embryonal day 15 and postnatal day 3, served as a model of neonatal lung injury. Single-transgenic non-Dox-responsive littermates were controls. CD34(+) cells (1 × 10(5) to 5 × 10(5)) were administered at postnatal day 5 by intranasal inoculation. Engraftment, respiratory epithelial differentiation, proliferation, and cell fusion were studied at 8 weeks after inoculation. Engrafted cells were readily detected in all recipients and showed a higher incidence of surfactant immunoreactivity and proliferative activity in FasL-overexpressing animals compared with non-FasL-injured littermates. Cord blood-derived cells surrounding surfactant-immunoreactive type II-like cells frequently showed a transitional phenotype between type II and type I cells and/or type I cell-specific podoplanin immunoreactivity. Lack of nuclear colocalization of human and murine genomic material suggested the absence of fusion. In conclusion, human CB-derived CD34(+) cells are capable of long-term pulmonary engraftment, replication, clonal expansion, and reconstitution of injured respiratory epithelium by fusion-independent mechanisms. Cord blood-derived surfactant-positive epithelial cells appear to act as progenitors of the distal respiratory unit, analogous to resident type II cells. Graft proliferation and alveolar epithelial differentiation are promoted by lung injury.     

Fas-induced apoptosis is a rare event in Sjögren's syndrome

The aim of this study was to perform a controlled in situ analysis on the incidence of apoptosis, investigate the expression of apoptosis-mediating proteins, and determine the frequency of apoptotic CD4+ and CD8+ T cells in Sj?gren's syndrome (SS). The study was extended to patients with atrophy-fibrosis (AF) not related to SS, as well as to a control group. Immunohistochemistry and the terminal deoxynucleotidyl transferase mediated dUTP digoxigenin nick end labeling (TUNEL) method were applied to study the Fas and FasL expression and the incidence of apoptosis in salivary glands (SG) from patients with primary and secondary SS, AF, and controls. These methods were also combined to enable simultaneous detection of apoptotic and CD4+ or CD8+ T cells. Despite abundant expression of Fas and FasL in SS SG, apoptotic cells were not exceeding 1% in the foci of infiltrating mononuclear cells (IMC). Double staining showed that the frequency of apoptosis was low among both CD4+ and CD8+ T cells. Only a few TUNEL+ epithelial cells were found in all patient groups. Fas was expressed predominantly on SS IMC, single SS epithelial cells, and a few normal acinar cells, but not in AF SG. Although FasL was present on SS and AF IMC and epithelial cells, it was rarely detected in normal tissue. Consequently we demonstrate that Fas-induced apoptosis among SS SG is a rare event. Our findings support an earlier hypothesis indicating that IMC seem to be able to escape apoptosis, resulting in foci of inflammatory cells. Notably, however, no obvious correlation can be drawn to previous studies where a high incidence of apoptosis of epithelial cells was proposed as an important mechanism leading to decreased glandular function, which is a hallmark of SS.     

Ineffective cellular immune response associated with T-cell apoptosis in susceptible Mycobacterium bovis BCG-infected mice

It has previously been reported that inhibition of delayed-type hypersensitivity-mediating functions of T cells during mycobacterial infection in mice is haplotype dependent. In the present study, we show that Mycobacterium bovis BCG infection induced, in susceptible C57BL/6 and BALB/c mice but not in resistant C3H/HeJ and DBA/2 mice, an important splenomegaly. An in vitro defect in T-cell proliferation in response to T-cell receptor (TCR) stimulation with mitogens or anti-CD3 antibodies was associated with enhanced levels of CD4(+) and CD8(+) T-cell apoptosis in susceptible but not in resistant mice 2 weeks after infection. Further investigations of C57BL/6 and C3H/HeJ mice revealed that in vivo splenomegaly was associated with destruction of the lymphoid tissue architecture, liver cellular infiltrates, and increased numbers of apoptotic cells in both spleen and liver tissue sections. Infection of C57BL/6 mice but not of C3H/HeJ mice induced massive production of tumor necrosis factor alpha (TNF-alpha) in serum, as well as an increase in Fas and Fas ligand (FasL) expression in T cells. In vitro addition of neutralizing anti-TNF-alpha antibodies led to a significant reduction in CD3-induced T-cell apoptosis of both CD4(+) and CD8(+) T cells of C57BL/6 mice, while the blockade of Fas-FasL interactions reduced apoptosis only in CD4(+) but not in CD8(+) T cells. Together, these results suggest that TNF-alpha and Fas-FasL interactions play a role in the activation-induced cell death (AICD) process associated with a defect in T-cell proliferation of the susceptible C57BL/6 mice. T-cell death by apoptosis may represent one of the important components of the ineffective immune response against mycobacterium-induced immunopathology in susceptible hosts.     

Apoptosis of thyrocytes and effector cells during induction and resolution of granulomatous experimental autoimmune thyroiditis

Experimental autoimmune thyroiditis (EAT) with granulomatous histopathology (G-EAT) can be induced by cells from mouse thyroglobulin (MTg)-immunized donors activated in vitro with MTg and IL-12. G-EAT lesions reach maximum severity 18-21 days after cell transfer and, if some thyroid follicles remain, lesions almost completely resolve by day 35. CD8(+) cells are required for G-EAT resolution. To begin to determine the mechanisms involved in G-EAT resolution, apoptosis in thyroids was analyzed by TUNEL staining. Apoptotic thyrocytes and inflammatory cells were present in the thyroids of both CD8(+) and CD8-depleted recipient mice at day 19-21. By day 35, apoptotic cells were rare in thyroids of mice whose lesions had resolved; the few apoptotic inflammatory cells were generally in close proximity to thyroid follicles. Thyroids of CD8-depleted mice had ongoing inflammation at day 35 and most apoptotic cells were thyroid follicular cells. The expression of Fas and Fas ligand (FasL) mRNA in thyroids was also determined by RT-PCR in both CD8(+) and CD8-depleted recipient mice. Fas was expressed in normal thyroids and its expression was relatively constant throughout the course of disease. FasL mRNA was not expressed in normal thyroids. FasL mRNA expression generally correlated with G-EAT severity, being maximal at day 21 and diminishing as lesions resolved. However, FasL mRNA expression in thyroids of CD8-depleted mice in which resolution was delayed was decreased compared to thyroids of CD8(+) mice with comparable disease severity, suggesting that FasL expressed by CD8(+) cells may play a role in G-EAT resolution.     

牛磺酸对大鼠肢体缺血再灌注后肺损伤时细胞凋亡的影响

目的:从细胞凋亡的角度探讨肢体缺血再灌注(LIR)后急性肺损伤(ALI)的发病机制及牛磺酸的影响。方法:复制大鼠肢体缺血再灌注(LIR)损伤动物模型,采用TUNEL法、电泳法、半定量逆转录聚合酶链反应(SqRT-PCR)及免疫组织化学等技术观察LIR后肺损伤发生过程中,肺泡上皮及血管内皮细胞凋亡变化以及Fas/FasL系统蛋白质和mRNA表达的改变。结果:大鼠LIR后,肺泡上皮细胞和肺血管内皮细胞凋亡明显增加;肺组织Fas/FasLmRNA和蛋白质表达明显上调,DNA断链率、组织钙含量和活性氧(ROS)升高,且与肺泡上皮及血管内皮细胞凋亡的增加相一致。结论:肺泡上皮及血管内皮细胞凋亡以及Fas/FasL系统表达明显上调可能参与LIR后ALI的发生;牛磺酸可减少肺组织细胞凋亡,但并非通过影响Fas/FasL基因表达而实现其保护效应。     

TcR-alpha/beta(+) CD4(-)CD8(-) T cells in humans with the autoimmune lymphoproliferative syndrome express a novel CD45 isoform that is analogous to murine B220 and represents a marker of altered O-glycan biosynthesis

Autoimmune lymphoproliferative syndrome (ALPS), caused by inherited defects in apoptosis secondary to mutations in genes encoding Fas/CD95/APO-1 and Fas ligand (Fasl)/CD95L, is characterized by nonmalignant lymphadenopathy and splenomegaly, increased T cell receptor alpha/beta(+) CD4(-)CD8(-) T cells (alpha/beta(+) double-negative T cells [alpha/beta(+)-DNT cells]), autoimmunity, hypergammaglobulinemia, and cytokine abnormalities. The alpha/beta(+)-DNT cells are immunophenotypically and functionally similar to alpha/beta(+)-DNT cells that accumulate in lpr and gld mice, which bear genetic mutations in Fas and FasL. In these mice, alpha/beta(+)-DNT cells express the B-cell-specific CD45R isoform B220. We show that alpha/beta(+)-DNT cells of ALPS patients, with either Fas or FasL mutations, also express B220. In addition, also similar to LPR/gLD mice, they have an unusual population of B220-positive CD4(+) T cells. B220 expression, together with our finding of characteristic lectin binding profiles, demonstrates that cell surface O-linked glycoproteins have undergone specific modifications, which may have consequences for lymphocyte trafficking, cell-cell interactions, and access to alternative apoptosis pathways.