Regulation of apoptosis in immune cells

Burn-injury affects gut-associated lymphoid tissues derived CD4+ T cells

After scald burn-injury, the intestinal immune system responds to maintain immune balance. In this regard CD4+T cells in Gut-Associated Lymphoid Tissues (GALT), like mesenteric lymph nodes (MLN) and Peyer's patches (PP) respond to avoid immune suppression following major injury such as burn. Therefore, we hypothesized that the gut CD4+T cells become dysfunctional and turn the immune homeostasis towards depression of CD4+ T cell-mediated adaptive immune responses. In the current study we show down regulation of mucosal CD4+ T cell proliferation, IL-2 production and cell surface marker expression of mucosal CD4+ T cells moving towards suppressive-type. Acute burn-injury lead to up-regulation of regulatory marker (CD25+), down regulation of adhesion (CD62L, CD11a) and homing receptor (CD49d) expression, and up-regulation of negative co-stimulatory (CTLA-4) molecule. Moreover, CD4+CD25+ T cells of intestinal origin showed resistance to spontaneous as well as induced apoptosis that may contribute to suppression of effector CD4+ T cells. Furthermore, gut CD4+CD25+ T cells obtained from burn-injured animals were able to down-regulate naïve CD4+ T cell proliferation following adoptive transfer of burn-injured CD4+CD25+ T cells into sham control animals, without any significant effect on cell surface activation markers. Together, these data demonstrate that the intestinal CD4+ T cells evolve a strategy to promote suppressive CD4+ T cell effector responses, as evidenced by enhanced CD4+CD25+ T cells, up-regulated CTLA-4 expression, reduced IL-2 production, tendency towards diminished apoptosis of suppressive CD4+ T cells, and thus lose their natural ability to regulate immune homeostasis following acute burn-injury and prevent immune paralysis.

Acalypha wilkesiana extracts induce apoptosis by causing single strand and double strand DNA breaks

ETHNOPHARMACOLOGICAL RELEVANCE

The seeds of Acalypha wilkesiana have been used empirically by traditional healers in Southwest Nigeria together with other plants as a powder mixture to treat patients with breast tumours and inflammation.

AIM OF THE STUDY

There is an increasing interest among researchers in searching for new anticancer drugs from natural resources, particularly plants. This study aimed to investigate the anticancer properties of Acalypha wilkesiana extracts and the characteristics of DNA damage against brain and lung cancer cells.

MATERIALS AND METHODS

The antiproliferative activity of Acalypha wilkesiana extracts (ethyl acetate, hexane, and ethanol) was examined on human glioma (U87MG), human lung carcinoma (A549), and human lung fibroblast (MRC5) cells.

RESULTS

Cell viability MTT assay revealed that ethyl acetate extract of the plant possessed significant antiproliferative effects against both U87MG (GI(50)=28.03 ± 6.44 μg/ml) and A549 (GI(50)=89.63 ± 2.12 μg/ml) cells (p value<0.0001). The hexane extract was found to exhibit crucial antiproliferative effects on U87MG (GI(50)=166.30 ± 30.50 μg/ml) (p value<0.0001) but not on A549 cells. Neither plant extract possessed noticeable antiproliferative effects on the non-cancerous MRC5 cells (GI(50)>300 μg/ml). The ethanol extract showed no antiproliferative effects on any cell line examined. Haematoxylin & Eosin (H & E) staining and single cell gel electrophoresis (SCGE) comet assay confirmed that plant extract-treated cells underwent apoptosis and not necrosis. SCGE comet assays confirmed that plant extracts caused both single strand (SSB) and double strand (DSB) DNA breaks that led to the execution of apoptosis.

CONCLUSION

The extracts (especially ethyl acetate and hexane) of Acalypha wilkesiana possess valuable cytotoxic effects that trigger apoptosis in U87MG and A549 cancer cells through induction of DNA SSBs and DSBs.

Autoimmune lymphoproliferative syndrome due to FAS mutations outside the signal-transducing death domain: molecular mechanisms and clinical penetrance

PURPOSE

Autoimmune lymphoproliferative syndrome is a disorder of lymphocyte apoptosis. Although FAS molecules bearing mutations in the signal-transducing intracellular death domain exhibit dominant-negative interference with FAS-mediated apoptosis, mechanisms for pathology of non-death domain FAS mutations causing autoimmune lymphoproliferative syndrome are poorly defined.

METHODS

RNA stability, protein expression, ligand binding, and ability to transmit apoptosis signals by anti-FAS antibody or FAS ligand were determined for a cohort of 39 patients with non-death domain autoimmune lymphoproliferative syndrome. Correlations between mutation type and disease penetrance were established in mutation-positive family members.

RESULTS

Frameshifts or transcriptional stop mutations before exon 7 resulted in messenger RNA haploinsufficiency, whereas an amino-terminal signal sequence mutation and certain intracellular truncations prevented cell surface localization of FAS. All resulted in decreased FAS localization, inability to bind FAS ligand, and reduced FAS ligand-induced apoptosis. Extracellular missense mutations and in-frame deletions expressed defective FAS protein, failed to bind FAS ligand, and exhibited dominant-negative interference with FAS-mediated apoptosis. Mutation-positive relatives with haploinsufficient or extracellular mutations had lower penetrance of autoimmune lymphoproliferative syndrome clinical phenotypes than did relatives with death domain mutations.

CONCLUSION

We have defined molecular mechanisms by which non-death domain FAS mutations result in reduced lymphocyte apoptosis, established a hierarchy of genotype-phenotype correlation among mutation-positive relatives of patients with autoimmune lymphoproliferative syndrome, and demonstrated that FAS haploinsufficiency can lead to autoimmune lymphoproliferative syndrome.

Apoptosis of antigen-specific T lymphocytes upon the engagement of CD8 by soluble HLA class I molecules is Fas ligand/Fas mediated: evidence for the involvement of p56lck, calcium calmodulin kinase II, and Calcium-independent protein kinase C signaling pathways and for NF-kappaB and NF-AT nuclear translocation

The binding of soluble HLA class I (sHLA-I) molecules to CD8 on EBV-specific CTL induced up-regulation of Fas ligand (FasL) mRNA and consequent sFasL protein secretion. This, in turn, triggered CTL apoptosis by FasL/Fas interaction. Molecular analysis of the biochemical pathways responsible for FasL up-regulation showed that sHLA-I/CD8 interaction firstly induced the recruitment of src-like p56(lck) and syk-like Zap-70 protein tyrosine kinases (PTK). Interestingly, p59(fyn) was activated upon the engagement of CD3/TCR complex but not upon the interaction of sHLA-I with CD8. In addition, sHLA-I/CD8 interaction, which is different from signaling through the CD3/TCR complex, did not induce nuclear translocation of AP-1 protein complex. These findings suggest that CD8- and CD3/TCR-mediated activating stimuli can recruit different PTK and transcription factors. Indeed, the engagement of CD8 by sHLA-I led to the activation of Ca2+ calmodulin kinase II pathway, which eventually was responsible for the NF-AT nuclear translocation. In addition, we found that the ligation of sHLA-I to CD8 recruited protein kinase C, leading to NF-kappaB activation. Both NF-AT and NF-kappaB were responsible for the induction of FasL mRNA and consequent CTL apoptosis. Moreover, FasL up-regulation and CTL apoptotic death were down-regulated by pharmacological specific inhibitors of Ca2+/calmodulin/calcineurin and Ca2+-independent protein kinase C signaling pathways. These findings clarify the intracellular signaling pathways triggering FasL up-regulation and apoptosis in CTL upon sHLA-I/CD8 ligation and suggest that sHLA-I molecules can be proposed as therapeutic tools to modulate immune responses.

Haploinsufficiency, rather than the effect of an excessive production of soluble CD95 (CD95{Delta}TM), is the basis for ALPS Ia in a family with duplicated 3' splice site AG in CD95 intron 5 on one allele

Autoimmune lymphoproliferative syndrome type Ia (ALPS Ia) is caused by mutations in the CD95/APO1/FAS (TN-FRSF6) gene, which lead to a defective CD95 ligand (CD95L)-induced apoptosis. Soluble CD95 (sCD95) has been suggested to play an important role in the pathogenesis of diverse autoimmune and malignant diseases by antagonizing CD95L. Here we evaluate a family with 4 of its 5 members harboring an ex-6-3C-->G mutation that affects the splice cis regulatory region (cctacag/ex-6-->cctagag/ex-6) of the CD95 gene. The mutation causes skipping of exon-6, which encodes the transmembrane region of CD95, and thereby leads to an excessive production of sCD95 in all 4 affected individuals. The mutation is associated with a low penetrance of disease phenotype and caused mild and transient ALPS in one male patient whereas all other family members are completely healthy. In all family members with the mutation we found that the cell surface expression of CD95 was low and the activated T cells were resistant to CD95-induced apoptosis. Unexpectedly, excessive production or addition of sCD95 had no effect on the CD95-induced apoptosis in diverse cells. In contrast, increasing the surface expression of CD95 was able to correct the defect in apoptosis. Thus we conclude that the ALPS in the one male patient was caused by haploinsufficiency of membrane CD95 expression. Our data challenge the hypothesis that sCD95 causes autoimmunity.

Burn injury induces a change in T cell homeostasis affecting preferentially CD4+T cells

Burn injuries are known to be associated with altered immune functions, resulting in decreased resistance to subsequent infection. In the present study, we determined the in vivo changes in T cell homeostasis following burn injury. Two groups of mice were used: a sham-burn group receiving buprenorphine as an analgesic and a burn group receiving buprenorphine and subjected to burn injury on 20% of the total body surface area. Results showed an important decrease in splenocytes following burn injury. This decrease persisted for 5 days and was followed, at day 10, by a 63% increase in number of cells. In vivo cell proliferation, as determined by the incorporation of 5-bromo-2'-dexoxyuridine, showed a significant increase of cycling splenocytes between days 2 and 10 after burn injury. The percentage of CD4+ and CD8+ T cells in the spleen was altered for 10 days after thermal injury. Analysis of naive (CD62Lhigh CD44low) and effector/memory (CD62Llow CD44high) T cells showed a percent decrease, independent of the expression of CD4 or CD8 molecules. However, early activation markers, such as CD69+, were expressed only on CD4+ T cells after a number of days following injury. Even with an activated phenotype, 10 days post-burn injury, CD4+ naive T cells significantly increased spontaneous apoptosis, detected by using a fluorescent DNA-binding agent 7-amino-actinomycin D. CD8+ T lymphocytes did not express early activation markers and were more resistant to apoptosis. Using purified T cells, we have shown unresponsiveness at day 10. Overall, these results demonstrate that mechanisms of T cell homeostasis were perturbed following burn injury. However, after 10 days, this perturbation persisted only in CD4+ T cells.

HIV-1 Nef control of cell signalling molecules: multiple strategies to promote virus replication

HIV-1 has at its disposal numerous proteins encoded by its genome which provide the required arsenal to establish and maintain infection in its host for a considerable number of years. One of the most important and enigmatic of these proteins is Nef. The Nef protein of HIV-1 plays a fundamental role in the virus life cycle. This small protein of approximately 27 kDa is required for maximal virus replication and disease progression. The mechanisms by which it is able to act as a positive factor during virus replication is an area of intense research and although some controversy surrounds Nef much has been gauged as to how it functions. Its ability to modulate the expression of key cellular receptors important for cell activation and control signal transduction elements and events by interacting with numerous cellular kinases and signalling molecules, including members of the Src family kinases, leading to an effect on host cell function is likely to explain at least in part its role during infection and represents a finely tuned mechanism where this protein assists HIV-1 to control its host.

H1-A extracted from Cordyceps sinensis suppresses the proliferation of human mesangial cells and promotes apoptosis, probably by inhibiting the tyrosine phosphorylation of Bcl-2 and Bcl-XL

H1-A, a pure compound used in traditional Chinese medicine, is effective in the treatment of autoimmune disorders of MRL lpr/lpr mice. We have previously reported that after 8 weeks of oral therapy with H1-A, 40 microg/kg/day, MRL lpr/lpr mice demonstrated significantly less proteinuria, lower serum creatinine levels, and less renal mesangial proliferation than mice in an untreated group. To clarify the pharmacologic properties of H1-A, we studied its cellular and subcellular effects in cultured human mesangial cells. Our results show that H1-A inhibits cell proliferation and promotes the apoptosis of interleukin (IL)-1- and platelet-derived growth factor (PDGF)-BB-activated human mesangial cells in vitro. Uptake of tritiated thymidine was nearly totally suppressed by the addition of 12.5 micromol/L H1-A (counts per minute decreased from 3905 +/- 70 to 141 +/- 5). The population of S-phase cells decreased from 15.5% +/- 1.7% to 10.0% +/- 0.3%, and G0 + G1 phase cells increased from 68.8% +/- 0.07% to 74.6% +/- 0.05%. This suppression was not a result of cytotoxicity. Apoptosis of human mesangial cells was detectable after treatment with 12.5 or 25 micromol/L H1-A. Using immunoprecipitation and immunoblotting, we found that H1-A inhibits tyrosine phosphorylation of human mesangial proteins and that Bcl-2 and Bcl-XL were probably among these proteins. These findings suggest that H1-A modulates some subcellular signal-transduction pathways and changes the balance between proliferation and apoptosis of mesangial cells in vitro or in vivo. H1-A may be effective in the management of autoimmune disorders, and the modulation of the signal transduction proteins Bcl-2 and Bcl-XL may represent a target for future pharmacologic interventions.

sFas and sFas ligand and pediatric sepsis-induced multiple organ failure syndrome

The Fas-Fas ligand system is important for apoptosis of activated immune cells. Perturbation of this system occurs in diseases with dysregulated inflammation. Increased soluble Fas (sFas) occurs in systemic inflammatory response syndrome (SIRS) and can block apoptosis. Increased shedding of FasL (sFasL) occurs in viral infection and hepatitis. Although dysregulated inflammation is associated with sepsis-induced multiple organ failure (MOF) in children, a role for Fas has not been established. We hypothesize that 1) sFas will be increased in children with severe and persistent sepsis-induced MOF and will correlate with inflammatory markers suggesting a role for sFas in inflammatory dysregulation in severe sepsis, and 2) sFasL will be increased when viral sepsis or sepsis-induced liver failure-associated MOF is present in children. Plasma sFas, sFasL, IL-6, IL-10, nitrite + nitrates, and organ failure scores were measured on d 1 and d 3 in 92 children with severe sepsis and 12 critically ill control children. sFas levels were increased in severe sepsis, continued to increase in persistent MOF and nonsurvivors, and were correlated with serum inflammatory markers (IL-6, IL-10, nitrite + nitrate levels). In contrast, sFasL was not increased in severe sepsis and did not correlate with inflammation. sFasL was, however, increased in liver failure-associated MOF and in nonsurvivors, and was associated with viral infection. At autopsy, hepatocyte destruction and lymphocyte infiltration were associated with increased sFas and sFasL levels. sFas may interfere with activated immune cell death and contribute to dysregulation of inflammation, worsening outcome from severe sepsis. sFasL may contribute to hepatic injury and the development of liver failure-associated MOF.

Enhanced apoptosis of peripheral blood mononuclear cells in cardiac transplanted patients undergoing chronic immunosuppressive treatment

Apoptosis plays a major role in tissue transplantation because intact T-cell-apoptosis pathways are required for the induction of tolerance to allografts. Moreover, immunosuppressive agents commonly used in clinical transplantation medicine promote lymphocyte apoptosis inhibiting the expression and production of cytokines involved in lymphocyte survival. The aim of our study was to evaluate peripheral blood mononuclear cells (PBMC) spontaneous apoptosis in patients undergoing chronic immunosuppressive treatment after cardiac transplantation. PBMC obtained from patients (n = 31) and controls matched for age and sex (n = 25) were cultured for 72 h and apoptosis was evaluated by quantification of fragmented DNA, staining with Hoechst 33258 dye and annexin V binding. We also investigated Fas expression and FasL mRNA expression as well as the ability of an IgM anti-Fas antibody to induce apoptosis. Finally, we evaluated IL2 production induced by PHA and the ability of IL2 to prevent apoptosis. In patients, PBMC underwent enhanced spontaneous apoptosis in comparison with controls. However, we could not find any difference between patients and normals as regards the expression of Fas and of FasL mRNA, even if the cross-linking of the Fas molecule induced apoptosis in PBMC from patients, whereas it failed to induce cell death in normals. We also found that IL2 production was significantly decreased in patients and that the addition of IL2 to the culture medium reduced PBMC spontaneous apoptosis. Our findings suggest that in cardiac transplanted patients PBMC undergo enhanced spontaneous apoptosis, which may contribute to prevent allograft rejection.

Tumor necrosis factor modulates apoptosis of monocytes in areas of developmentally regulated bone remodeling

Tooth eruption is characterized by spatially segregated bone resorption along the path of eruption and bone formation in the opposite direction. Monocyte recruitment occurs in two distinct peaks in both areas of resorption and formation. Without such recruitment tooth eruption does not occur. The signals that regulate this recruitment are thought to involve the expression of cytokines and chemokines. One such cytokine is tumor necrosis factor (TNF), which can affect monocyte recruitment through the induction of chemokines and adhesion molecules and increase their lifespan by acting as antiapoptotic cell survival signals. We examined the latter by studying mice with targeted deletions of TNF receptors p55 and p75 (TNFRp55/p75). The results indicate that mice that lack functional TNF receptors have a significantly reduced number of monocytes in the apical area associated with bone formation. The reduced number of monocytes in this area can be accounted for by an increase in apoptosis in TNFRp55-/-/p75-/-. In contrast, the number of monocytes, the rate of monocyte apoptosis, and the formation of osteoclasts in the occlusal area associated with bone resorption occurred independently of TNF activity. These results suggest that TNF receptor signaling can affect tooth eruption by acting as a monocyte survival signal in some but not all areas of bone undergoing developmentally regulated remodeling.

The significance of immunohistochemistry in the diagnosis and therapy of neoplasms

This review article details the diagnostical significance of immunohistochemistry, which has developed during the last quarter of the century. Certainly, the advancement of monoclonal antibody technology has been of great significance in assuring the place of immunohistochemistry in the modern accurate microscopic diagnosis of human neoplasms, as a method of choice in histopathology. The fact still remains that in order to properly assess any immunohistochemical reactivity used for differential diagnostic purposes, the target cells have to be identified as neoplastically transformed cells by routine histopathological techniques. Selected groups of target molecules of great significance in cancer biology are discussed. The discovery of neoplasm-associated antigens has not only made the more accurate diagnosis of human cancer feasible but has also shed light on the extensive immunophenotypical heterogeneity of even the most closely linked human malignancies. The identification of disseminated neoplastically transformed cells by immunohistochemistry has allowed for a clearer picture of cancer invasion and metastasis, as well as the evolution of the tumour cell associated immunophenotype towards increased malignancy. Some possibilities of neoplasm-associated antigen targeted, receptor-directed immunotherapy are discussed and reviewed in this manuscript. Future antineoplastic therapeutical approaches should see the inclusion of a variety of immunotherapies, in the form of an individualised 'cocktail' specific for the particular immunophenotypical pattern associated with each individual patient's neoplastic disease.

Heightened intrathecal release of soluble CD137 in patients with multiple sclerosis

Human CD137 (ILA/4-1BB), a member of the tumour necrosis factor (TNF) receptor family, regulates the activation and proliferation of immune cells, and may induce apoptosis (programmed cell death) of activated lymphocytes. A soluble form of CD137 (sCD137) released by activated lymphocytes may interfere with the activities of the membrane-bound CD137. This study reports the detection of significantly high intrathecal and systemic levels of sCD137 in patients with clinically active multiple sclerosis (MS) when compared with corresponding levels from patients with clinically stable MS or those with inflammatory and non-inflammatory neurological disorders, or from healthy individuals. Intrathecal concentrations of sCD137 in patients with active MS correlate with the intrathecal release of the soluble death receptor protein Fas, but not with the release of interleukin-2, TNF or the synthesis of immunoglobulins G and M. Results presented here suggest that heightened release of sCD137 is a feature of clinically active MS.

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.

Immunocytochemical detection of leukocyte-associated and apoptosis-related antigen expression in childhood brain tumors

During systematic cell-surface antigen expression profile analyses of 76 primary childhood brain tumors [34 medulloblastomas (MED)/primitive neuroectodermal tumors (PNETs) and 42 astrocytomas (ASTR)], a library of monoclonal antibodies (MoABs) directed against various leukocyte-associated, lymphocyte cell-line differentiation antigens in childhood brain tumors was utilized. The antigens were detected employing an indirect, biotin-streptavidin conjugated alkaline phosphatase (AP) immunocytochemical technique. Major histocompatibility complex (MHC) class I restricted, tumor-associated antigen (TAA) specific, CD8(+) cytotoxic T lymphocytes (CTL) were identified in 58/76 (76.32%) brain tumors, and usually represented 1-10% of all cells, but in some cases 30-44% of the cells were CD8(+). CD4(+), MHC class II restricted helper lymphocytes were present in 65/76 (85.53%) brain tumors, and accounted for 1-10% of the observed cells. Macrophages were present in 74/76 (97.37%) brain tumors, and their number also represented 1-10% of all observed cells in the brain tumor frozen sections. Leukocyte common antigen (LCA) expression was detected in all 76 (100%) brain tumors studied. MoAB UJ 308 detected the presence of premyelocytes and mature granulocytes in 60/76 (78.95%) brain tumors. Natural killer (NK) cells were not defined in the observed brain tumors. The great majority of childhood glial tumors, particularly ASTRs express Fas (APO-1/CD95) receptor whereas normal cells in the central nervous system (CNS) do not. FasR is a transmembrane glycoprotein which belongs to the nerve growth factor/tumor necrosis factor (NGF/TNF) receptor superfamily. As part of our screening, the 42 childhood ASTRs were also investigated for expression of CD95. We detected strong expression (strong intensity of staining, number of stained cells 50-100%) of FasR, employing formalin fixed, paraffin-wax embedded tissue slides. Brain tumors and melanomas have been shown to produce their autocrine FasL, and are even capable of switching CD95-related signal transduction from the PCD pathway to a proliferative pathway. In view of our results, we conclude that: (1) the tumor infiltrating leukocytes in MEDs/PNETs and ASTRs represent a very diverse population and are present in a great majority of the cases studied; (2) the strong expression of FasR in ASTRs provides a manner in which T lymphocytes may exert their anti-tumor effects, but may also represent yet another way that tumors may evade the immune response; and (3) further observations of the expression of various antigens involved in juxtacrine, in situ growth control are necessary for the refinement of cellular immunotherapeutical approaches in the treatment of human malignancies.

IgD receptor-mediated signal transduction in T cells

Upregulation of immunoglobulin D-specific receptors (IgD-R) on CD4+ T cells may facilitate their interaction with specific carbohydrate moieties uniquely associated with membrane IgD on B cells. Previous studies have shown that upregulation of IgD-R facilitates cognate T-B cell interactions by mediating bidirectional signaling resulting in increased antibody responses and clonal expansion of antigen-specific T cells. Murine T hybridoma cells, 7C5, constitutively express IgD-R, as has been confirmed by staining with biotinylated IgD. Earlier studies have shown that inhibitors of protein tyrosine kinase (PTK) completely prevented upregulation of IgD-R in response to oligomeric IgD, suggesting that cross-linking of IgD-R may induce signal transduction and functional consequences through one or more PTK activation pathways, leading to upregulation of IgD-R. In the present study we show that cross-linking of IgD-R by oligomeric IgD indeed results in (a) T cell activation as seen by tyrosine phosphorylation of several intracellular proteins, (b) tyrosine phosphorylation of p56 Lck and PLC-gamma in 7C5 T hybridoma cells, and (c) phosphorylation of an approximately 29-kDa band that exhibits strong affinity for IgD. We analyzed tyrosine phosphorylation of p56 Lck and PLC-gamma in BALB/c splenic T cells that were exposed to oligomeric IgD both in vivo and in vitro. In vitro cross-linking as well as in vivo followed by in vitro cross-linking of IgD-R resulted in enhanced phosphorylation of p56 Lck and moderate tyrosine phosphorylation of PLC-gamma. These results suggest that interactions between IgD-R and IgD mediate signal transduction and support our previous findings that IgD-R+ T cells enhance cognate T cell-B cell interactions and antibody production.

Soluble HLA class I/CD8 ligation triggers apoptosis in EBV-specific CD8+ cytotoxic T lymphocytes by Fas/Fas-ligand interaction

In the present study, we report that allogeneic soluble HLA class I (sHLA-I) molecules isolated from serum induce apoptosis on EBV-specific CD8(+) Fas(+) cytotoxic T lymphocytes (CTL). CTL apoptosis is induced by the binding of sHLA-I molecules to CD8 and its extent depends on the time of incubation with sHLA-I molecules. Apoptosis is triggered by the interaction of Fas(+) CTL with soluble Fas-ligand, which is released following the binding of sHLA-I antigens to CD8 molecules. These results suggest that sHLA-I molecules may regulate immune responses by inducing apoptosis in virus-specific CTL.

Relationships between T lymphocyte apoptosis and anergy following trauma

BACKGROUND

Severely injured trauma patients experience T cell depletion. A subset of these patients also develop T cell unresponsiveness (anergy), as characterized by the failure of their T cells to proliferate or to produce T lymphokines in response to a direct stimulus through the T cell receptor. We hypothesized that T cell apoptosis plays a role in the development of posttrauma T cell depletion and/or T cell anergy by deleting an activated T cell population. We found that moderately increased T cell depletion posttrauma is not innately deleterious or immediately responsible for anergy, but may predispose to later development of T cell anergy, possibly due to a more stringent requirement for activation of the remaining naive T cells.

METHODS

A total of 30 blunt trauma and burn patients were assessed twice weekly for the following parameters: (1) clinical outcome expressed as severity of organ dysfunction as measured by the multiple organ dysfunction syndrome score, (2) proliferative response of highly purified T cells to anti-CD3/anti-CD4, (3) level of apoptosis as determined by flow cytometric analysis of propidium iodide-stained monocyte reduced peripheral blood mononuclear cells, either unstimulated or in response to mitogenic challenge or Fas (CD95) stimulation.

RESULTS

A wide range of apoptosis levels are seen in the patients' T cells. Apoptosis is increased when all trauma patients' T cells are compared to T cells of normal volunteers. However, at the time a patients' T cells are anergic, there is no increased level of apoptosis. In fact, the point of maximum anergy (lowest proliferative response) correlates to diminished apoptotic response. Increased T cell apoptosis can be stimulated by anti-Fas antibody in trauma patients' responsive T cells but not in maximally anergic T cells. These data suggest that patients' T cell anergy is not an immediate result of apoptotic T cell depletion upon stimulation. However, patients who later develop T cell anergy have increased T cell apoptosis earlier in their clinical course than patients who never experience T cell anergy.

CONCLUSIONS

Increased levels of apoptosis are not directly associated with negative trauma patient outcome nor the immediate cause of T cell anergy. However, unusually high levels of apoptosis and development of severe T cell depletion occurring before complete activation and expansion of the posttrauma T cell response may presage anergy and subsequent organ failure.

Calorie restriction increases Fas/Fas-ligand expression and apoptosis in murine splenic lymphocytes

One-month-old male ICR mice were fed a nutritionally adequate, semipurified diet, either ad libitum (AL) or calorie restricted (CR) (40% less food) for 6 months and were killed to obtain spleens. Flow cytometric analysis revealed increased proportions of both CD4+ and CD8+ T cells in CR-fed mice compared to AL-fed mice. The T cell subsets of CR-fed mice were also found to have higher levels of plasma membrane Fas receptor expression. Similarly, Fas-ligand (Fas-L) expression was higher in anti-CD3-stimulated CD4+ and CD8+ T cells. CR-fed mice also had increased numbers of annexin V-positive CD4+ and CD8+ T cells in stimulated splenic lymphocytes suggesting an increased potential for apoptosis. Fas and Fas-L gene expression in splenic lymphocytes, which correlated closely with the observed increased rate of apoptosis, was significantly increased in CR-fed mice compared to AL-fed mice. In conclusion, these results indicate that CR increases the expression of Fas and Fas-L which may contribute to the known beneficial effects of CR such as prolongation of life span by activating chronic physiologically mediated apoptosis.

Induction of apoptosis and apoptotic mediators in Balb/C splenic lymphocytes by dietary n-3 and n-6 fatty acids

The present study was designed to investigate the effect of dietary n-6 and n-3 polyunsaturated fatty acids (PUFA) on anti-CD3 and anti-Fas antibody-induced apoptosis and its mediators in mouse spleen cells. Nutritionally adequate semipurified diets containing either 5% w/w corn oil (n-6 PUFA) or fish oil (n-3 PUFA) were fed to weanling female Balb/C mice, and 24 wk later mice were sacrificed. In n-3 PUFA-fed mice, serum and splenocyte lipid peroxides were increased by 20 and 28.3% respectively, compared to n-6 PUFA-fed mice. Further, serum vitamin E levels were decreased by 50% in the n-3 PUFA-fed group, whereas higher anti-Fas- and anti-CD3-induced apoptosis (65 and 66%) and necrosis (17 and 25%), compared to the n-6 PUFA-fed group, were found when measured with Annexin V and propidium iodide staining, respectively. In addition, decreased Bcl-2 and increased Fas-ligand (Fas-L) also were observed in the n-3 PUFA-fed group compared to the n-6 PUFA-fed group. No difference in the ratio of splenocyte subsets nor their Fas expression was observed between the n-3 PUFA-fed and n-6 PUFA-fed groups, whereas decreased proliferation of splenocytes was found in n-3 PUFA-fed mice compared to n-6 PUFA-fed mice. In conclusion, our results indicate that dietary n-3 PUFA induces higher apoptosis by increasing the generation of lipid peroxides and elevating Fas-L expression along with decreasing Bcl-2 expression. A reduced proliferative response of immune cells also was observed in n-3 PUFA-fed mice.

Apoptosis-associated generation of reactive oxygen intermediates and release of pro-inflammatory cytokines in human lymphocytes and granulocytes by extracts from the seeds of Acalypha wilkesiana

Seeds from Acalypha wilkesiana (Euphorbiaceae) are an essential component of a complex plant mixture used empirically by traditional healers in Southwest Nigeria to treat breast tumours and inflammation. To investigate their biological properties, we incubated human lymphocytes and granulocytes with aqueous and ethanolic extracts of A. wilkesiana seeds (AWS). In lymphocytes, we observed an induction of apoptosis and generation of reactive oxygen intermediates (ROI), as measured by the oxidation of hydroethidine, within 2 h, while in granulocytes, an aqueous seed extract induced the oxidative burst and enhanced phagocytosis of Escherichia coli within 10-20 min. In the supernatants of 72-h cultured lymphocytes, AWS induced the release of the pro-inflammatory cytokines tumour necrosis factor-alpha and interleukin-6, and also T-cell-associated cytokines interleukin-5 and interferon-gamma. These preliminary results encourage further investigations of this drug with both cytotoxic and immunomodulating properties.

Age-related changes in the expression of CD95 (APO1/FAS) on blood lymphocytes

Aging is associated with alterations of the immune system, thought to be related to an increased susceptibility to infectious diseases, and possibly to cancer and autoimmunity in the elderly. In the present paper we report data obtained on freshly collected blood from 148 healthy subjects of different ages (from cord blood to 102 years old). The subjects were divided into seven age classes (cord blood, 3-11 years, 15-39 years, 41-60 years, 61-74 years, 75-84 years, 85-102 years) and their lymphocyte subsets and the expression of the apoptosis-related molecule CD95 were evaluated. In respect of lymphocyte subsets, the major differences were found in the cord-blood samples compared with the oldest old groups. In the cord-blood group, the absolute number of all the lymphocyte subsets was enhanced, but in the oldest group, an increase of CD16+ lymphocytes was observed, whereas CD19+ lymphocytes, which progressively decrease with age, continue to decrease further in the very old. The data show that the expression of CD95 increases until age 74 years, whereas in the oldest old it tends to decrease again. The trend of CD95 expression seems to be related to the change of expression of CD95 on CD4+ lymphocytes, because the CD8+/CD95+ population rose steadily throughout the entire age range. The evaluation of CD95+/CD45R0+ lymphocytes shows similar results to those observed analyzing CD95 on total lymphocytes. Furthermore, a constant increase of CD95+/CD28+ and a related decline of CD28+ lymphocytes was observed in all age groups. These data suggest that the expression of CD95 on the different subsets of lymphocytes can be considered a good marker for studies of immunosenescence, because it may be predictive of successful aging, and can partially explain the change in lymphocytes subsets in elderly.

Ectopic expression of B7-1 (CD80) on T lymphocytes in autoimmune lpr and gld mice

Defective Fas-mediated apoptosis in mice, caused by the gld mutation in the fas ligand gene, results in the development of lupus-like autoantibodies and severe lymphoproliferation. We previously demonstrated ectopic expression of the costimulatory molecule B7-1 (CD80) on T lymphocytes in B6/gld mice. This report extends these observations by demonstrating similar results in B6/lpr mice, which possess a mutation in the gene encoding Fas. Additionally, we demonstrate that this phenomenon is age-dependent and occurs on multiple subsets of B6/gld T lymphocytes. B7-1 upregulation is observed on T cells from both conventionally housed and specific-pathogen-free B6/gld mice, suggesting that this is not a consequence of infection by pathogen. T cells from lpr and gld mice show increased binding of CTLA4-Ig fusion protein, suggesting that the upregulated B7-1 is functional. CD28, a receptor for B7-1 which activates T cells, is upregulated in B6/lpr and B6/gld mice, while CTLA4, a negative regulator of T cells which binds B7-1, is not. Our results suggest that ectopic expression of B7-1 on T cells of lpr and gld mice may be playing a role in exacerbation of lymphoproliferation and/or autoimmunity.

Galectin-1, a natural ligand for the receptor-type protein tyrosine phosphatase CD45

Galectin-1 binds preferentially to N-acetyllactosamine residues on oligosaccharides associated with several cell surface glycoconjugates. In the present work, placental galectin-1 has been identified to be a natural ligand for the receptor-type protein tyrosine phosphatase CD45. The binding of galectin-1 to CD45 was detected by affinity chromatography of NP 40 solubilized Jurkat T cell membranes on galectin-1 agarose followed by immunoblotting of the galectin-1 agarose bound fraction applying monoclonal antibodies to CD45 isoforms. The PTPase activity of the galectin-1 agarose binding membrane fraction could be inhibited by sodium orthovanadate. Preincubation of Jurkat T cell membrane preparations with galectin-1 decreased the membrane-associated PTPase activity in a concentration-dependent manner. Incubation of Jurkat cells with galectin-1 suppressed the immunoprecipitated PTPase activity of CD45. Galectin-1 stimulates the cell surface expression of phosphatidylserine an early indicator of apoptosis. In CD45+ Jurkat T cells, galectin-1 induces higher levels of phosphatidylserine when compared with CD45- Jurkat cells. These observations indicate that galectin-1-mediated ligation of CD45 is involved in the induction of apoptosis in Jurkat T cells.

Aging splenocyte and thymocyte apoptosis is associated with enhanced expression of p53, bax, and caspase-3

Aging is associated with altered immune function. We previously reported that splenocytes and thymocytes undergo apoptosis with aging in rats. In the present study, we examined the expression of genes associated with apoptosis in splenocytes and thymus in aging rats. We evaluated the expression of bax, interleukin 1-beta-converting enzyme (ICE)/ced-3 protease family, caspase-3 and tumor suppressor gene p53. Rats in age groups of 6, 24, 48, and 96 weeks were sacrificed; thymocytes and splenocytes were isolated followed by lysis in a modified RIPA buffer containing protease inhibitors. Western blot analysis of proteins was performed by probing immunoblots with antibodies against p53, bax and PARP (poly ADP-ribose polymerase). Increased aging was associated with enhanced expression of bax, p53 and cleavage of PARP by Caspase-3. The expression of p53 and cleavage of PARP indicates the presence of damaged DNA; nevertheless, the cleavage of PARP or activation of caspase-3 may be playing an important role in the initiation of early events in apoptosis. These results suggest that aging of splenocytes and thymocytes is associated with the expression of cell death genes. The present study provides an insight into age-associated altered immune function.

Neuronal death and survival in two models of hypoxic-ischemic brain damage

Two unilateral hypoxic-ischemia (HI) models (moderate and severe) in immature rat brain have been used to investigate the role of various transcription factors and related proteins in delayed neuronal death and survival. The moderate HI model results in an apoptotic-like neuronal death in selectively vulnerable regions of the brain while the more severe HI injury consistently produces widespread necrosis resulting in infarction, with some necrosis resistant cell populations showing evidence of an apoptotic type death. In susceptible regions undergoing an apoptotic-like death there was not only a prolonged induction of the immediate early genes, c-jun, c-fos and nur77, but also of possible target genes amyloid precursor protein (APP751) and CPP32. In contrast, increased levels of BDNF, phosphorylated CREB and PGHS-2 were found in cells resistant to the moderate HI insult suggesting that these proteins either alone or in combination may be of importance in the process of neuroprotection. An additional feature of both the moderate and severe brain insults was the rapid activation and/or proliferation of glial cells (microglia and astrocytes) in and around the site of damage. The glial response following HI was associated with an upregulation of both the CCAAT-enhancer binding protein alpha (microglia only) and NFkappaB transcription factors.

Examining a paradox in the pathogenesis of human pulmonary tuberculosis: immune activation and suppression/anergy

Protective immunity against Mycobacterium tuberculosis (MTB) in animal models is based on cell-mediated immunity (CMI), involving bi-directional interactions between T cells and cells of the monocyte/macrophage (MO/MA) lineage. Key factors include MO-derived interleukin (IL)-12 and tumor necrosis factor (TNF)-alpha as well as T cell derived IL-2 and interferon (IFN)-gamma. These cytokines appear particularly crucial in the induction of MA-mediated elimination of mycobacteria. Several lines of evidence indicate that similar mechanisms are operating in humans. During active pulmonary tuberculosis (PTB), signs of both immune depression and immune activation are concomitantly present. Decreased tuberculin skin test reactivity in vivo and deficient IFN-gamma production by MTB-stimulated mononuclear cells in vitro are observed. On the other hand, the serum levels of several cytokines, including TNF, and other inflammatory mediators are increased and circulating MO and T cell show phenotypic and functional evidence of in vivo activation. In this review, we will discuss the evidence for three models, which could explain this apparent paradox: 1. Stimulation of the T cell-suppressive function from MO/MA; 2. Intrinsic T cell refractoriness, possibly associated with tendency to apoptosis (programmed cell death), and 3. Compartmentalization and redistribution of immune responses to the site of disease. The opportunistic behavior of MTB during human immunodeficiency virus (HIV) infection can be explained by suppression of type-1 responses at the level of antigen-presenting cells, CD4 T cells and effector macrophages. The ominous prognostic significance of intercurrent PTB during HIV infection seems primarily due to prolonged activation of HIV replication in macrophages. Supportive immune therapy during PTB could aim at correcting the type-1 deficiency either by IFN-gamma inducers (e.g. IL-12, IL-18) or by neutralizing the suppressive cytokines transforming growth factor beta (TGF-beta) and IL-10. Alternatively, inflammatory over-activity could be reduced by neutralizing TNF. Finally, anti-apoptotic therapies (e.g. IL-15) might be considered.

Induction of apoptosis by the N-acetyl-galactosamine-specific toxic lectin from Viscum album L. is associated with a decrease of nuclear p53 and Bcl-2 proteins and induction of telomeric associations

The ribosome-inhibiting proteins from Viscum album L., i.e. the mistletoe lectins (ML), were recognized to induce apoptosis in various tumour cell lines and human lymphocytes. However, several aspects of ML-induced cell death are unclear. We report that the galNAc-binding ML III incubated with human lymphocytes mediates a very effective death signal resulting in the binding of Annexin-V and expression of mitochondrial membrane proteins Apo2.7, but also in an influx of the DNA intercalating dye propidium iodide. The addition of the ribosome-inhibiting protein Volkensin also induced Apo2.7 molecules, while Momordin, lacking a carbohydrate-binding chain, did not enter the cell membrane and thus did not affect the cells. However, we observed ML III to preferentially affect CD8+ cells with a memory phenotype (CD62L(lo)) as compared to their CD8+ CD62L(hi) counterparts, CD4+ T cells and CD19+ B cells. Furthermore, ML III did not induce sister chromatid exchange-inducing DNA lesions but reduced the intensity of telomeric signals, increased the frequencies of telomeric associations and C-anaphases and reduced nuclear Bcl-2 and p53 proteins. Whatever the exact mechanisms are, our results provide strong evidence that the ML III-mediated cytotoxicity involves distinct killing pathways, i.e. (1) primary cell death via an induction of apoptosis which may not be dependent on protein and/or RNA synthesis and may not involve p53 and Bcl-2 proteins and (2) a loss of telomeres resulting in chromosomal instability in the surviving cells which is incompatible with life. However, we cannot exclude the possibility that this effect is due to a decrease in nuclear p53 proteins.

Increased spontaneous apoptosis in T lymphocytes in DiGeorge anomaly

The aim of this study was to determine whether increased apoptosis in peripheral blood lymphocytes plays a role in T cell deficiency associated with DiGeorge anomaly. T cell subsets from a patient with DiGeorge anomaly were examined for the expression of Fas, FasL, Bcl-2 and Bcl-XL at the protein level with monoclonal antibodies, using dual-colour flow cytometry, and at the mRNA level in mononuclear cells by quantitative reverse transcriptase-polymerase chain reaction. In vitro spontaneous apoptosis was examined by propidium iodide staining and DNA fragmentation, using flow cytometry and gel electrophoresis, respectively. Fas and FasL expression, both at the level of protein and of mRNA, was increased, whereas Bcl-2 expression was decreased both at the level of protein and of mRNA. However, no difference in Bcl-XL expression was observed between the patient and an age-matched control. A significant proportion of both CD4+ and CD8+ T cells from the patients underwent spontaneous apoptosis, whereas almost no spontaneous apoptosis was observed in the age-matched control. These data suggest that spontaneous apoptosis in T lymphocytes, at least in part, may be responsible for T cell deficiency in DiGeorge anomaly.

Apoptosis and ageing

Stimulation of T cells from aged individuals leads to different kinds and/or size of responses if compared with the responses of T cells obtained from young individuals. In fact elderly is associated with a progressive decline of immune response besides an increasing incidence of autoimmune phenomena. These differences might be the result of modified cellular mechanisms controlling the immune system in the course of ageing. The apoptotic deletion of activated T cells has been proposed as the key mechanism to maintain T cell homeostasis, and in this respect CD95 (Fas antigen) seems to play a major role in this course of events. In this study we show that just collected lymphocytes from old subjects displayed an increased expression of the apoptosis molecule CD95. The expression of CD95 and the spontaneous apoptosis showed the same trend. In fact the percentage of apoptotic cells in blood collected from old subjects was enhanced too. The lymphocyte subpopulation analysis by flow cytometry did not show significant changes in T subset percentages between old and young subjects. Moreover mononuclear cells obtained from aged individuals underwent apoptosis in culture in response to a single stimulation with mitogen or anti-CD3, more than mononuclear cells from young controls. To gain insight into mechanisms of this increased apoptosis, experiments were performed to evaluate the behaviors of lymphocytes from old and young donors in respect of interleukin-2 (IL-2) rescue from apoptosis. Results show that IL-2 rescued only a little fraction of cells of old donors from apoptosis when activated by anti-CD3 and that this effect was not related to a different expression of CD95. Thus, during the course of ageing the different regulation of T cell homeostasis might be also explained by the modified proneness of lymphocytes to undergo apoptosis. The contemporaneous demonstration of a reduced Ca2+ influx in lymphoid cells of these subjects allows to suppose that multiple defects play a role in the pathogenesis of immunosenescence.

Human eosinophils express bcl-2 family proteins: modulation of Mcl-1 expression by IFN-gamma

The expression of the Bcl-2 family proteins Bax, Mcl-1, Bcl-2, and Bcl-xL, was examined in human peripheral blood eosinophils or in umbilical-cord-blood-derived eosinophils. Immunoblot analysis disclosed high amounts of the proapoptotic factor Bax in freshly purified eosinophils of both types. Although cord-blood-derived eosinophils expressed easily detectable levels of Mcl-1, Bcl-2, and Bcl-xL, only traces or no expression of these three antiapoptotic proteins were found in peripheral blood eosinophils. Incubation of both eosinophil types for 1 to 3 days in a cytokine-deprived medium led to apoptosis, without changes in the expression of Bax, Mcl-1, Bcl-2, or Bcl-xL. Although addition of interleukin-5 or interferon-gamma (IFN-gamma) to the culture medium increased the survival of both eosinophil types, a rise in the levels of Mcl-1 was observed only in IFN-gamma-treated cord-blood eosinophils. Together, these results indicate that human eosinophils have a specific profile of Bcl-2-family protein expression that depends on their maturation status and may be modulated by stimuli that influence their survival.

Increased Apoptosis of T Cell Subsets in Aging Humans: Altered Expression of Fas (CD95), Fas Ligand, Bcl-2, and Bax

Aging is associated with lymphopenia and progressive decline in T cell functions; however, the mechanisms underlying these defects are unclear. We analyzed the expression of genes promoting apoptosis (fas/fasL1 and bax) and those inhibiting apoptosis (bcl-2 and bcl-xL) in lymphocytes from aging and young subjects at the protein level, using flow cytometry/Western blotting, and at the mRNA level, using quantitative PCR. Susceptibility of T cell subsets to undergo anti-Fas-induced apoptosis was analyzed by propidium iodide staining, TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling) assay, DNA fragmentation assay, and staining with Hoechst 33342 dye. An increased expression of Fas and Fas ligand and a decreased expression of Bcl-2 were observed in both CD4+ and CD8+ T cells from aging as compared with young controls. Increased Fas and decreased Bcl-2 expression were also found in memory cells of both CD4+ and CD8+ T cell subsets from aging. Bax expression was increased in lymphocytes from aging at both the protein and mRNA level. No significant difference was observed in Bcl-xL expression between aging and young; however, the ratio of Bax:Bcl-xL was increased in aging. An increased proportion of CD4+ and CD8+ T cell subsets from aging underwent apoptosis following anti-Fas Ab treatment as compared with CD4+ and CD8+ T cell subsets from young controls. These data suggest that increased apoptosis may be one of the mechanisms responsible for lymphopenia and T cell deficiency associated with human aging.

Apoptosis as a mechanism of peripheral blood mononuclear cell death after measles and varicella-zoster virus infections in children

Viral infections may induce an acquired form of immunodeficiency, generally lasting a few weeks. In the more severe form, such as HIV infection, the immunodeficiency is permanent. Programmed death of T cells represents one of the mechanisms by which HIV determines the T cell functional impairment, finally resulting in the destruction of T cells. In this study, we evaluated whether an altered regulation of apoptosis was also implicated in the anergy associated with the common measles or varicella-zoster virus (VZV) infections in infancy. A spontaneous apoptosis of peripheral blood mononuclear cells was observed in children who had suffered from these infections as long as 6 mo after the acute disease. Apoptosis was demonstrated through analysis of cellular DNA content, morphologic evidence of cell nuclei shrinkage, and by analysis of DNA degradation. Stimulation of T cells through anti-CD4 MAb increased the number of apoptotic cells with a maximal effect 72 h after the stimulation. Our results suggest that apoptosis may account for the anergy that follows acute viral infections in infancy.

DNA fragmentation is a feature of cystic fibrosis epithelial cells: a disease with inappropriate apoptosis?

Cystic fibrosis (CF) is a single-gene disease caused by mutations in the CFTR gene, which result in disrupted chloride secretions with inspissated mucous secretions by exocrine glands. Nick-end labelling was used to assess DNA fragmentation in 14 CF and 24 control duodenal samples, and in two CF and two control lung tissues. In CF small intestine median 46% (range: 30-82) villus enterocytes show DNA fragmentation (vs. 3% (range: 1-7) in controls P < 0.001) and median 37.5% (range: 23-79) crypt enterocytes show Ki67 antigen (P < 0.001). In CF airways 57% (range: 54-70) of epithelial cells show DNA fragmentation. Inappropriate high DNA fragmentation is a feature of various CF epithelia. This could have great impact in understanding the mechanisms leading to disease.

The expression of genes modulating programmed cell death in normal human polymorphonuclear neutrophils

Normal human polymorphonuclear neutrophils (PMN) have a short life and die in progression via apoptosis. In order to understand the molecular basis of PMN apoptosis, the expression of apoptosis-related (Fas, Fas-ligand, p53, and c-myc) and survival-related (bcl-2) genes was detected by flow cytometry, Western blot and reverse transcription-assisted polymerase chain reaction (RT-PCR). We found that Fas and Fas-ligand (FasL) were expressed on the surface of most of the cells. However, the disappearance of FasL was much faster than Fas after 24 h incubation. p53 and bcl-2 were also expressed in the cytoplasm of most of the cells. In contrast, the expression of c-myc was negligible in PMN. The addition of monoclonal anti-human Fas antibody (25 micrograms/ml) to PMN suspension enhanced whereas anti-FasL antibody (25 micrograms/ml) suppressed PMN apoptosis in 48 h incubation. These results suggest that the activation of Fas pathway induced by Fas-FasL interaction among PMNs is one of the mechanisms for spontaneous PMN apoptosis. Lack of proto-oncoprotein c-myc expression in PMN is responsible for their non-proliferative property and may aggravate the spontaneous apoptosis of the cells.

Increased apoptosis of CD45RO- T cells with aging

Increasing susceptibility to infectious and autoimmune phenomena have long been recognized to accompany advancing age in otherwise healthy individuals. Recently animal models of aging have suggested that age-associated immune dysfunction may correlate with defects in T cell apoptosis. We have examined activation-induced apoptosis defects in human peripheral T cells from young individuals (mean age = 31 +/- 3 years old) compared to aged individuals (mean age = 67 +/- 8 years old). Following in vitro activation of T cells with PHA and IL-2, apoptosis was measured in T cell subsets using 7-amino actinomycin D (7-AAD) staining and analysis via three colour flow cytometry. There was no significant difference in apoptosis of the total CD3+ T cell population at early and late time points. Interestingly, increased apoptosis in the CD3+ CD45RO- T cell population of older adults was observed by culture day 6. While the total number of CD3+ CD45RO- cells was not different between young (< 33 years) and old (> 65 years) individuals, 32% of these cells did not undergo apoptosis in younger individuals while only 10% of these cells avoided this fate in older individuals. These results suggest that accumulation of CD45RO+ T cells may occur in aged subjects due in part to preferential elimination of CD45RO- cells with activation. Furthermore, as new or continued immune response requires differentiation of CD45RO+ T cells to CD45RO+ T cells after activation, increased apoptosis instead of survival in aged individuals could lead to observed T cell immune deficiency.

Estrogen decreases in vitro apoptosis of peripheral blood mononuclear cells from women with normal menstrual cycles and decreases TNF-alpha production in SLE but not in normal cultures

Estrogen has been suspected of causing changes in the lupus disease process by an as yet undetermined mechanism. In vitro apoptosis of peripheral blood mononuclear cells (PBMCs) in short-term unstimulated cultures of systemic lupus erythematosus (SLE) cells is accelerated compared to that in cells from normal individuals. To determine whether estrogen might be involved in regulating the rate of apoptosis in lupus, PBMCs or T cells from women with or without normal menstrual cycles were cultured for 16-20 hr with or without 30 ng/ml estradiol. The rate of apoptosis of the cells was measured, and supernatants of these cultures were tested for various cytokines known to affect apoptosis directly or indirectly. Compared to untreated cultures, estrogen significantly reduced in vitro apoptosis of both patient (P < 0.05, n = 12) and normal (P < 0.001, n = 14) PBMCs if the donors had normal menstrual cycles. Estrogen did not decrease apoptosis of noncycling patient (n = 8) nor of normal (n = 11) cells. Apoptosis of T cells cultured alone was not affected by estrogen. Supernatants from patients' estrogen-treated PBMCs had significantly less TNF-alpha than untreated cultures (P < 0.05, n = 12). TNF-alpha levels from normals' cell cultures were unchanged. Changes in hormone status (hysterectomy or menopause) alter estrogen-sensitive apoptosis, which may be mediated through monocytes. Estrogen-induced decreases in apoptosis combined with decreased TNF-alpha production in the presence of estrogen may allow survival of auto-immune cells in SLE patients.

Missense Mutations in the Fas Gene Resulting in Autoimmune Lymphoproliferative Syndrome: A Molecular and Immunological Analysis

Programmed cell death (or apoptosis) is a physiological process essential to the normal development and homeostatic maintenance of the immune system. The Fas/Apo-1 receptor plays a crucial role in the regulation of apoptosis, as demonstrated by lymphoproliferation in MRL-lpr/lpr mice and by the recently described autoimmune lymphoproliferative syndrome (ALPS) in humans, both of which are due to mutations in the Fas gene. We describe a novel family with ALPS in which three affected siblings carry two distinct missense mutations on both the Fas gene alleles and show lack of Fas-induced apoptosis. The children share common clinical features including splenomegaly and lymphadenopathy, but only one developed severe autoimmune manifestations. In all three siblings, we demonstrated the presence of anergic CD3+CD4−CD8− (double negative, [DN]) T cells; moreover, a chronic lymphocyte activation was found, as demonstrated by the presence of high levels of HLA-DR expression on peripheral CD3+ cells and by the presence of high levels of serum activation markers such as soluble interleukin-2 receptor (sIL-2R) and soluble CD30 (sCD30).

N-acetylcysteine protects lymphocytes from nitrogen mustard-induced apoptosis

The ability of the antioxidant N-acetylcysteine to prevent apoptosis induced in lymphocytes by nitrogen mustard (HN2) was investigated. HN2 caused a concentration-dependent induction of apoptosis on C3H murine spleen cells, as identified by two criteria: morphological features revealed by microscopical observations and DNA fragmentation visualized by the characteristic "ladder" pattern observed upon agarose gel electrophoresis, as well as by hypodiploid DNA-containing cells revealed by the flow cytometric analysis of propidium iodide labelled cells. The antioxidant N-acetylcysteine (NAC) was found to markedly reduce the occurrence of HN2-induced apoptosis in these cells. This protective effect will still obtained when NAC was added 30 min after HN2. In contrast, the pretreatment of spleen cells with this antioxidant did not provide any significant protection. We also showed that lymphocytes protected by NAC are still able to respond to a mitogenic stimulation. To gain some insight into the mechanisms underlying the cytoprotective action of NAC against HN2, we tested whether or not poly(ADP-ribose) polymerase (PARP, EC 2.4.2.30), a nuclear enzyme that participates in the triggering of apoptosis induced by alkylating agents, is involved. We report that 6(5H)-phenanthridinone, a potent PARP inhibitor, did not affect the ability of NAC to prevent HN2-induced apoptosis under our experimental conditions. Thus, the exact mechanism by which NAC protects lymphocytes from HN2 cytotoxicity has yet to be determined.