凋亡抑制蛋白XIAP和促凋亡因子Smac在胰腺癌化疗抵抗中的作用

目的探讨x-相关凋亡抑制蛋白（XIAP）和促凋亡因子Smac在胰腺癌细胞化疗抵抗中的作用，以及转染胞浆表达型Smac基因靶向下凋XIAP对化疗药物诱导的胰腺癌细胞凋亡的影响。方法应用流式细胞术检测顺铂、5-FU介导的Panc-1、BXPC-3的凋亡率及胞浆染色分析细胞XIAP表达变化，Western blot分析XIAP、Smac、Caspase-3表达水平；构建pEGFP-NI／Smac真核表达载体并转染胰腺癌Panc-1细胞，流式细胞术检测转染Smac基因前后Panc-1细胞的凋亡敏感性。结果与BXPC-3细胞相比，Panc-1对顺铂或5-FU介导的凋亡具有较强抵抗性，Western blot分析显示Panc-1细胞高表达XIAP，在化疗药物作用下化疗敏感细胞BXPC-3胞浆内XIAP水平下降明显多于Panc-1细胞，而且凋亡的BXPC-3细胞释放入胞浆内的成熟Smac蛋白水平明显高于Panc-1细胞。转染胞浆表达型Smac基因至化疗抵抗Panc-1细胞，可明显下调其XIAP表达水平，促进效应Caspase-3分子活化，显著提高顺铂、5-FU诱导的细胞凋亡率。结论胰腺癌细胞XIAP的表达水平下调与其化疗敏感性有关，XIAP是克服化疗抵抗的重要靶分子，而上调Smac活性蛋白的胞浆表达作为一种有效调节信号，通过拮抗XIAP的凋亡抑制作用协同化疗药物促进胰腺癌细胞凋亡。     

紫杉醇联合奥沙利铂对非小细胞肺癌模型小鼠的治疗作用

目的观察紫杉醇联合奥沙利铂对荷瘤裸鼠非小细胞肺癌治疗效果以及对PDCD5和XIAP表达的影响。方法制备裸鼠肺癌荷瘤模型,将荷瘤小鼠随机分为空白组、0.9%氯化钠溶液组、奥沙利铂组、紫杉醇组和紫杉醇联合奥沙利铂组;q-PCR检测各组PDCD5和XIAP基因表达水平;Western bolt分析各组PDCD5和XIAP蛋白表达情况;对比分析各组肿瘤组织重量。结果紫杉醇联合奥沙利铂组PDCD5 mRNA表达水平最高(P0.01),XIAP mRNA表达水平最低(P0.01);紫杉醇联合奥沙利铂组PDCD5蛋白表达最高(P0.01),XIAP蛋白表达最低(P0.01);对比各分组肿瘤组织重量,紫杉醇联合奥沙利铂组肿瘤质量最小(P0.01)。结论紫杉醇联合奥沙利铂化疗能显著增加PDCD5表达和降低XIAP表达,能使已发生的非小细胞肺癌组织质量显著减少。     

下调X连锁调亡抑制蛋白基因表达增强多西他赛诱导膀胱癌细胞凋亡的作用

目的: 观察人源性膀胱癌细胞在下调X连锁凋亡抑制蛋白(XIAP)基因表达后,多西他赛对其敏感性的影响。方法: 以shRNA和shRNA-XIAP质粒分别稳定转染人源性膀胱癌T24T细胞。以荧光显微镜观察转染细胞。以RT-PCR和Western blotting法分别检测膀胱癌细胞XIAP mRNA和蛋白的表达。与T24T以及转染空载体的T24T细胞相比较,以ATPase法检测多西他赛对转染 XIAP 基因的膀胱癌细胞的细胞毒性。相差显微镜下观察,流式细胞术检测多西他赛预处理转染 XIAP 基因的膀胱癌细胞的凋亡率;以Western blotting法检测细胞内的聚腺苷二磷酸核糖聚合酶(PARP)和caspase-3蛋白表达和裂解水平。结果: 荧光显微镜下分别观察shRNA和shRNA-XIAP转染的T24T细胞,均见稳定荧光。Western blotting和RT-PCR检测结果显示,人源性膀胱癌T24T细胞在稳定转染反义XIAP基因后,其XIAP蛋白和mRNA水平均显著降低。经多西他赛处理24 h后, 转染反义XIAP基因的T24T细胞IC₅₀为(1.23±0.62)nmol/L,远低于T24T以及转染空白载体的对照组细胞 。流式细胞术检测结果显示, T24T shRNA-XIAP细胞组(2 nmol/L和5 nmol/L)凋亡率 显著高于转染空载体细胞的凋亡率 。与转染空载体的细胞相比较,T24T shRNA-XIAP细胞内的PARP和caspase-3明显降低。结论: 下调膀胱癌细胞的XIAP基因表达后,可显著增强化疗药物多西他赛所诱导的膀胱癌细胞的凋亡,并增强多西化赛的细胞毒性。     

XIAP在鼻咽癌细胞株CNE1、CNE2和5-8F中的表达与研究

目的比较CNE1、CNE2及5-8F鼻咽癌细胞株中X链锁调亡抑制蛋白(XIAP)的表达差异。方法体外培养鼻咽癌细胞株CNE1、CNE2及5-8F,采用RT-PCR法检测CNE1、CNE2及5-8F细胞株中XIAP基因表达情况。结果 XIAP基因在CNE1低表达,而在CNE2和5-8F高表达。结论 XIAP与NPC的恶性程度和转移潜能有关。     

小干扰RNA下调白血病细胞X连锁凋亡抑制蛋白的表达及其对化疗药物敏感性的影响

目的 探讨小干扰RNA(siRNA)下调白血病MOLT-4、HL-60、K562细胞的白血病细胞X连锁凋亡抑制蛋白(XIAP)的表达对化疗药物敏感性的影响.方法 采用实时荧光定量PCR和Western免疫印迹检测MOLT-4、HL-60、K562细胞及健康人外周血单个核细胞(PBMC)XIAP mRNA和XIAP蛋白表达水平.用NucleofectorTM核酸转染仪对高表达XIAP的K562细胞转染XIAP siRNA(实验组),同时以转染无同源性siRNA作阴性对照组,未转染任何siRNA的K562细胞作空白对照组,并检测3组细胞XIAP mRNA和XIAP蛋白表达水平.同时将实验组、阴性及空白对照组细胞暴露于不同浓度的依托泊苷(vp-16,0.01、0.1、1、10、100mg/L)及阿糖胞苷(Ara-c,0.1、1、10、100、1000、10 000mg/L),用CCK-8法检测细胞抑制率变化.结果 与健康人PBMC比较,MOLT-4、HL-60、K562细胞XIAPmRNA及蛋白表达均增高(均P＜0.05),其中K562细胞XIAPmRNA及蛋白表达水平最高,与MOLT-4、HL-60细胞比较差异有统计学意义(均P＜0.05).K562细胞转染XIAP siRNA48 h后,与阴性对照组、空白对照组比较,实验组细胞XIAP mRNA及蛋白表达水平均明显下降(mRNA:0.37±0.10比1.41±0.13比1.00±0.12,蛋白:0.37±0.03比0.99±0.08比0.98±0.07,均P＜0.05).在给予1 mg/L vp-16、10及100 mg/L的Ara-c后,实验组细胞抑制率与阴性对照组、空白对照组比较,差异有统计学意义(均P＜0.05);在给予其他浓度vp-16和Ara-c后,3组细胞抑制率差异均无统计学意义(均P＞0.05).结论 XIAP siRNA能特异性下调K562细胞XIAPmRNA和蛋白质水平的表达,增强K562细胞对化疗药物依托泊苷、阿糖胞苷的敏感性.     

Pathomorphological peculiarities of damage to hair cells of the organ of Corti in experimental sensorineural hearing loss

Pathomorphology of the organ of Corti was studied on models of acute and chronic sensorineural damage to the acoustic analyzer. Peculiarities of hair cell degeneration, necrosis, and apoptosis in the organ were studied by light and scanning electron microscopy. The type of pathomorphological substrate in abnormalities of the organ of Corti depends on the intensity of the destructive exposure, but not on the nature of otopathological factors. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 141, No. 3, pp. 356–360, March, 2006     

Immunohistochemical detection of X-linked inhibitor of apoptosis in head and neck squamous cell carcinoma

The X-linked inhibitor of apoptosis (XIAP) is the most potent member of the IAP group of structurally related caspase inhibitors. Experimental and clinical evidence implicates XIAP in resistance to cancer therapy and in clinical aggressiveness of certain tumors. We examined the expression of XIAP in head and neck squamous cell carcinoma (SCC). Four-micrometer sections from 59 routinely processed specimens of head and neck SCC were subjected to citrate-based antigen retrieval, followed by incubation with monoclonal anti-XIAP antibody (BD Biosciences, San Jose, Calif) and EnVision Plus reagents (Dako, Carpinteria, Calif). Granular cytoplasmic staining was considered positive; the extent and intensity of staining were recorded. Normal squamous epithelium was either nonstaining (n=22), displayed generally weak basal staining (n=9), or moderate basal staining (n=1). Squamous dysplasia or carcinoma in situ was either nonstaining (10 of 18 cases) or displayed generally weak staining (8 of 18 cases). Varying degrees of XIAP positivity were found in 41 (69.5%) of 59 carcinomas. Most of the nonstaining and weakly staining carcinomas were well or moderately differentiated. In contrast, intense and extensive staining was most frequently found in poorly differentiated carcinomas. In keratinized tumor nests, staining was strongest peripherally and became diminished in central keratinized zones. New parameters of tumor aggressiveness are needed for more effective triaging of patients to appropriately aggressive therapies. The present findings suggest that the potent apoptotic inhibitor XIAP may be such a biomarker in head and neck SCCs, of resistance to apoptosis-inducing therapies, and, possibly, of responsiveness to a new class of XIAP-suppressive drugs presently in clinical trials for other malignancies or in preclinical development.     

凋亡抑制蛋白Livin在肾癌组织中的表达及其意义

目的观察凋亡抑制蛋白Livin在肾癌组织内的表达情况,分析Livin的表达与肾癌临床病理特征之间的关系。方法应用免疫组化法和Westernblot技术观察Livin在肾癌组织内的表达。结果 Livin在肾癌组织及正常肾组织中均有表达,Livin蛋白表达于肿瘤细胞胞质,在48例肾癌组织中Livin阳性表达率为79.2%,对照组16例正常肾组织中Livin阳性表达率为18.8%,二者之间差别具有统计学意义(<0.05)。Westernblot检测结果表明在肾癌组织中Livin蛋白的表达量显著高于正常肾组织的表达水平(<0.05)。Livin表达与患者性别、年龄、肿瘤分化程度无关,与临床分期和淋巴结转移显著相关(<0.05)。Kaplan-Meier生存分析结果表明,Livin阴性患者无瘤生存率明显高于Livin阳性患者(<0.05)。结论 Livin在肾癌组织高表达与肾癌的进展和淋巴结转移密切关系,可能预示肾癌复发。     

Opposing responses of apoptosis and autophagy to moderate compression in skeletal muscle

Aim: The molecular mechanism that contributes to the pathogenesis of deep pressure ulcer remains to be elucidated. This study tested the hypotheses that: (1) apoptosis and autophagy are activated in compression‐induced muscle pathology and (2) apoptotic and autophagic changes precede pathohistological changes in skeletal muscle in response to prolonged moderate compression. Methods: Adult Sprague–Dawley rats were subjected to an experimental model of pressure‐induced deep tissue injury. Static pressure of 100 mmHg was applied to an area of 1.5 cm² over the mid‐tibialis region of right limb of rats for one single session of 6‐h compression (1D) or two sessions of 6‐h compression over two consecutive days with rats sacrificed one day (2D) or immediately after (2D‐IM) the compression. The left uncompressed limb served as the intra‐animal control. Muscle tissues underneath compression region were collected for analysis. Results: Our histological analysis indicated that pathohistological characteristics including rounding contour of myofibres and massive nuclei accumulation were apparently demonstrated in muscles of 2D and 2D‐IM. In contrast, these pathohistological changes were generally not found in muscle following 1D. Apoptotic DNA fragmentation, terminal dUTP nick‐end labelling index and caspase‐3 protease activity were significantly elevated in compressed muscles of all groups. Caspase‐9 enzymatic activity was found to be significantly increased in compressed muscles of 2D and 2D‐IM whereas increase in caspase‐8 activity was exclusively found in compressed muscle of 1D. According to our immunoblot analysis, FoxO3 was significantly reduced in compressed muscles of all groups whereas Beclin‐1 was decreased only in 2D. LC3‐I was significantly reduced in compressed muscles of all groups while LC3‐II was decreased in 2D and 1D. No significant differences were found in the protein abundance of Akt and phospho‐Akt in muscles among all groups. Conclusion: These data demonstrate the opposing responses of apoptosis and autophagy to moderate compression in muscle. Moreover, our findings suggest that cellular changes in apoptosis and autophagy have already taken place in the very early stage in which apparent histopathology has yet to develop in the process of compression‐induced muscle pathology.     

The influences of sphingolipid metabolites on gentamicin-induced hair cell loss of the rat cochlea

Sphingolipid metabolites inducing ceramide, sphingosine, and sphingosine-1-phosphate (S1P) play important roles in the regulation of cell proliferation, survival, and death. Aminoglycoside antibiotics including gentamicin induce inner ear hair cell loss and sensorineural hearing loss. Apoptotic cell death is considered to play a key role in this injury. The present study was designed to investigate the possible involvement of ceramide and S1P in hair cell death due to gentamicin. In addition, the effects of other metabolites of ceramide, gangliosides GM1 (GM1) and GM3 (GM3), on gentamicin ototoxicity were also investigated. Basal turn organ of Corti explants from p3 to p5 rats were maintained in tissue culture and exposed to 20 or 35 μM gentamicin for 48 h. The effects of ceramide, S1P, GM1, and GM3 on gentamicin-induced hair cell loss were examined. Gentamicin-induced hair cell loss was increased by ceramide but was decreased by S1P. GM1 and GM3 exhibited protective effects against gentamicin-induced hair cell death at the limited concentrations. These results indicate that ceramide enhances gentamicin ototoxicity by promoting apoptotic hair cell death, and that S1P, GM1, and GM3 act as cochlear protectants. In conclusion, sphingolipid metabolites influence the apoptotic reaction of hair cells to gentamicin ototoxicity.     

62例胰腺癌组织中细胞凋亡的特征

目的研究拟阐明凋亡与胰腺癌分型、分期、分化程度、术后生存期的关系。方法62例胰腺癌标本取自1999年1月至2002年1月中国医科大学第二临床学院普外科及辽宁省人民医院普外科，术后病理证实。22例正常胰腺组织为上述医院的解剖标本。TUNEL法检测正常胰腺组织、胰腺癌组织内的凋亡细胞。结果在22例正常胰腺组织中细胞凋亡率为4／22，程度为（＋）；在62例胰腺癌组织中细胞凋亡阳性率为72．6％（45／62），程度为（＋）～（＋＋＋）。凋亡阳性率在胰腺癌组织分型、分期之间无统计学意义；高分化胰腺癌凋亡阳性率高于低分化胰腺癌（P〈0．05），中分化胰腺癌凋亡阳性率高于低分化胰腺癌（P〈0．01）；高、中分化胰腺癌之间差异无统计学意义；在中、高分化胰腺癌中，细胞凋亡程度（＋＋）～（＋＋＋）与（-）～（＋）的病例术后生存时间比较，前者显著长于后者（P〈0．05）。结论凋亡主要影响胰腺癌的发展、转移及预后；细胞凋亡在一定程度上阻止胰腺癌进展，最终延长胰腺癌患者生存时间。因此采用不同方法诱导胰腺癌组织中细胞凋亡可能为胰腺癌综合治疗提供新思路。     

Regulation of apoptosis and T cell activation by Fas-specific mAb

Fas was initially described as a molecule expressed on the surfaceof certain cell lines that could mediate programmed cell death(apoptosis) subsequent to ligatlon by specific mAb. To determinewhether mAb to other epitopes on the Fas molecule might mediateother functions, we generated a panel of mAb to the extracellularportion of human Fas. Significant lysis of Fas-expressing targetcells was only observed when the new mAb were first bound toa solid-phase support and not when the mAb were added in solution.However, several of these mAb inhibited the killing of targetcells induced by the prototypic Fas-specific mAb, CH-11. ThosemAb that inhibited apoptosis of target cells mediated by theCH-11 mAb also blocked lysis of target cells mediated by cellsexpressing Fas ligand. Finally, some of the Fas-specific mAbwere found to co-stimulate proliferation of peripheral bloodT cells in the presence of immobilized CD3 mAb. Thus, the dataindicate the existence of a complex set of interactions mediatedby Fas in both normal and transformed lymphoid cells that mayhave important implications regarding the role(s) of this moleculein regulation of immune responses.     

Programmed cell death (apoptosis) as a mechanism of cell death in peripheral blood mononuclear cells from cats infected with feline immunodeficiency virus (FIV).

FIV is a lentivirus infection of cats which induces an immunodeficiency syndrome associated with early qualitative defects in antigen-specific T cell function and with late quantitative defects in CD4+ T lymphocytes. We have observed that peripheral blood mononuclear cells (PBMC) from FIV-infected cats have impaired survival in culture. The mechanism of this in vitro dysfunction and depletion is not known. We have proposed that inappropriate induction of programmed cell death (apoptosis) could account for these in vitro defects. Here, we report that PBMC from FIV-infected cats, with impaired T cell blastogenesis and impaired survival in vitro, undergo an active cell death upon culture, which has the morphological and biochemical characteristics of programmed cell death (PCD). Apoptosis occurred in all six asymptomatic FIV-infected cats, and in none of the nine uninfected cats, which were studied. Changes in cell morphology under both light and electron microscopy, and fragmentation of genomic DNA were characteristic for apoptosing cells. Cell death was spontaneous and occurred in the absence of any stimuli, and culture with the T cell mitogen, concanavalin A (Con A), did not significantly enhance cell death. Activation-induced cell death was inhibited, in a dose-dependent manner, by addition to the incubation medium of zinc, which has been shown to inhibit the action of endonuclease responsible for the characteristic fragmentation of DNA. Since apoptosis has recently been implicated in AIDS pathogenesis, FIV infection may prove useful to study this aspect of retroviral, in particular HIV, infection.     

Elevations in cytosolic free Ca2+ are not required to trigger apoptosis in human leukaemia cells.

Previous studies have indicated that Ca2+ is a trigger for apoptosis (programmed cell death) in thymocytes and related cell lines. Recently we have shown that levels of apoptosis in leukaemic cells are diminished in Ca(2+)-deficient conditions, indicating that Ca2+ may be important in the mechanism of apoptosis in these cells. In the present study we investigated the possibility that Ca2+ serves as a trigger for apoptosis in the human leukaemic cell line, HL-60. Using fura-2 to measure cytosolic free Ca2+ concentrations, [Ca2+]i, in cell suspensions, and by using ratio imaging of fura-2 in single cells, we did not observe an early significant increase in [Ca2+]i in HL-60 cells undergoing apoptosis. The latter stages of apoptosis were, however, accompanied by increasing [Ca2+]i; these increases were apparently a result of, rather than a cause of, apoptosis. Furthermore, apoptosis could be induced in HL-60 cells under conditions of vastly reduced [Ca2+]i achieved by loading these cells with fura-2 in the presence of EGTA. These results indicate that elevation of [Ca2+]i is not a prerequisite for apoptosis in HL-60 cells and that apoptosis can occur in these cells in the presence of low [Ca2+]i.     

Aspergillus fumigatus conidia inhibit tumour necrosis factor- or staurosporine-induced apoptosis in epithelial cells

A major innate immune response to inhaled conidia of the opportunistic pathogen Aspergillus fumigatus (Af) is the synthesis of pro-inflammatory cytokines, which include tumour necrosis factor (TNF)-alpha, a known inducer of apoptosis. Modulation of host cell apoptosis has been reported to be one of the mechanisms whereby pathogens overcome host cell defences. Our study was designed to investigate whether or not Af conidia could modulate apoptosis induced by TNF-alpha or staurosporine (STS). Exposure of epithelial cells treated by these inducers and exposed to Af conidia decreased the number of apoptotic cells detected by Annexin V staining, analysis of nuclear morphology, terminal deoxynucleotidyl transferase-mediated fluorescein-dUTP nick end-labelling reaction and immunoblotting. Inhibition of apoptosis by Af conidia was seen in cells of the A549 pneumocyte II line, human tracheal epithelial 16HBE and primary human respiratory cells. Inhibition of apoptosis by Af conidia was also observed when apoptosis was induced by co-cultivating A549 cells with activated human alveolar macrophages. Unlike Af conidia, conidia of Cladosporium cladosporioides as well as latex beads or killed Af conidia have no inhibitory effect on TNF-alpha or STS-induced apoptosis. For TNF-induced apoptosis, the observed anti-apoptotic effect of Af conidia was found to be associated with a significant reduction of caspase-3.     

RIP1在细胞程序性死亡中作用的研究进展

近期研究发现受体相互作用蛋白（receptor—interacting protein,RIP）是细胞生存和死亡的重要交叉点,在细胞的凋亡与存活、程序性坏死等过程中发挥着关键性的作用。RIP1为RIP家族中的第一个成员,是一种重要的细胞信号转导调控分子。RIP1的结构与生物学功能及在细胞程序性死亡中的作用具有重要意义。     

Cell death by apoptosis in acute leukaemia

We have previously demonstrated that when freshly isolated childhood T-cell acute lymphoblastic leukaemia cells are incubated in growth medium after isolation from blood, chromatin is rapidly cleaved into nucleosomal sized fragments that are multiples of 200 bp. The fragmentation is similar to that observed in other types of cells undergoing apoptosis or programmed cell death. In this study we describe a more comprehensive approach to the study of DNA fragmentation in leukaemia. Fragmentation was observed in freshly isolated cells from patients with T-cell acute lymphoblastic leukaemia and in one with common acute lymphoblastic leukaemia. Frozen samples of T-cell acute lymphoblastic leukaemia, common acute lymphoblastic leukaemia, and acute myeloid leukaemia cells also showed fragmentation of DNA. However, no fragmentation was evident in normal leukocytes treated under the same conditions. Ultrastructural studies on the isolated leukaemia cells demonstrate that the chromatin cleavage observed biochemically is associated with morphological changes characteristic of apoptosis.     

Analysis of lymphocyte cell death and apoptosis in HIV-2-infected patients.

Recent evidence suggests that T cell apoptosis could be involved in the pathogenesis of HIV-1 infection. As the progression of HIV-2 associated disease appears to be slower than that of HIV-1, we investigated whether there were differences in the degree of T cell death and apoptosis in peripheral blood mononuclear cell (PBMC) cultures from patients with HIV-1 or HIV-2 infection. PBMC from healthy controls (n = 28) and patients infected with HIV-1 (n = 26: asymptomatic (ASY)/persistent generalized lymphadenopathy (PGL), n = 16; and AIDS-related complex (ARC)/AIDS n = 10) or HIV-2 (n = 30: ASY/PGL, n = 16; ARC/AIDS, n = 14) were cultured in the absence or presence of mitogens (PHA, PWM) or superantigen (SEB). After 48 h, cell death (CD) was assessed by trypan blue exclusion and in some patients programmed cell death (PCD) was quantified in flow cytometry by measuring the percentage of hypodiploid nuclei corresponding to fragmented DNA, after treating the cells with a propidium iodide hypotonic solution. HIV-1 and HIV-2 ARC/AIDS patients and ASY/PGL HIV-1+ patients had significant increases in cell death percentages compared with controls, both in unstimulated and stimulated lymphocyte cultures. However, HIV-2+ ASY/PGL patients did not exhibit significant increases of cell death in unstimulated cultures. In addition, the comparison between HIV-1 and HIV-2 infected subjects in similar stages of disease, showed no significant differences in CD in the ARC/AIDS patients, although ASY/PGL HIV-2 infected subjects had lower levels of CD than the HIV-1+ ASY/PGL (3.4% +/- 0.6 s.e.m. versus 6.8% +/- 1.1 s.e.m., P < 0.01). PCD was significantly increased both in ASY/PGL (14.3% +/- 2.2 s.e.m., n = 8, P < 0.005) and in ARC/AIDS (25.3% +/- 4.5 s.e.m., n = 9, P < 0.001) HIV-1+ patients compared with healthy controls (5.8% +/- 1.7 s.e.m., n = 11). This contrasts with HIV-2 infected subjects where the ASY/PGL patients (10.0% +/- 2.8 s.e.m., n = 6) did not differ significantly from healthy controls, although ARC/AIDS patients (27.2% +/- 4.2 s.e.m., n = 9, P < 0.001) had significantly increased levels of PCD. In conclusion, this is the first report describing the occurrence of spontaneous and activation-induced lymphocyte death by apoptosis in HIV-1 infected subjects.(ABSTRACT TRUNCATED AT 400 WORDS)