In vitro cytotoxicity of CD8+ T cells in multi-drug-resistant tuberculosis. A preliminary report

Background and objective:   Specific CD8+ T-cell cytotoxicity has been recognized as being involved in the elimination of drug-susceptible tuberculosis (DS-TB). Given that there is currently no information on the cytotoxic effector functions of CD8+ T cells in multi-drug-resistant tuberculosis (MDR-TB), our objective was to analyse the cytotoxic activity, both basal and stimulated, of CD8+ T cells from MDR-TB patients and compare it with that of DS-TB patients, as well as purified protein derivative (PPD)+ and PPD− subjects.
Methods:   Cytotoxic activity of CD8+ T cells from MDR-TB patients, DS-TB patients, PPD+ and PPD− subjects was measured by a colorimetric assay, using H37Rv culture filtrate protein as the antigenic stimulus.
Results:   Twenty-eight subjects were studied (7 MDR-TB patients, 7 DS-TB patients, 7 PPD+ subjects and 7 PPD− subjects). In the presence of the antigenic stimulus, the cytotoxic activity of CD8+ T cells from MDR-TB patients (% lysis) increased from 6.7% to 59.6% ( P  < 0.001). In DS-TB patients lysis increased from 3.2% to 22.5% ( P  < 0.001), whereas in PPD+ subjects it increased from 2.7% to 12.0% ( P  < 0.001) and in PPD− subjects from 1.3% to 3.2% ( P  < 0.001). Basal cytotoxic activity was significantly higher for MDR-TB patients than PPD+ and PPD− subjects ( P  = 0.003), but not compared with that for DS-TB patients ( P  = 0.05). Stimulated cytotoxic activity was highest for MDR-TB patients.
Conclusions:   CD8+ T cells from MDR-TB patients showed an exaggerated cytotoxic activity after antigenic stimulation. Further studies are required to elucidate the role of this response in the immunopathogenesis of MDR-TB.     

Interferon-gamma and interleukin-4 reciprocally regulate CD8 expression in CD8+ T cells

The CD8 co-receptor can modulate CD8⁺ T cell function through its contributions to T cell receptor (TCR) binding and signaling. Here we show that IFN-γ and IL-4 exert opposing effects on the expression of CD8α mRNA and surface CD8 protein during CD8⁺ T cell activation. IL-4 caused down-regulation of surface CD8 on ovalbumin (OVA)_257–264-specific TCR-transgenic OT-I CD8⁺ T cells activated with OVA_257–264-coated antigen presenting cells or polyclonal stimuli, and on wild type CD8⁺ T cells activated with polyclonal stimuli. This effect was enhanced in each case when the cells lacked a functional IFN-γ or IFN-γR gene. When WT or IFN-γ-deficient OT-I CD8⁺ T cells were analyzed 9 days after co-injection with control or IL-4-expressing OVA⁺ tumor cells into RAG-2^−/−γc^−/− mice, CD8 levels were highest on WT donor cells from mice that received the control tumor and lowest on IFN-γ-deficient donor cells from mice that received the IL-4-expressing tumor. The latter CD8^low cells displayed markedly impaired binding of OVA_257–264/MHC tetramers and peptide/MHC-dependent degranulation. The data reveal an unexpected role for IFN-γ in tuning the CD8 co-receptor during primary CD8⁺ T cell activation both in vitro and in vivo.     

Recruitment of CD8+ T cells expressing granzyme A is associated with lesion progression in human cutaneous leishmaniasis

Human infection with Leishmania braziliensis leads to the establishment of cutaneous leishmaniasis (CL), characterized by the appearance of skin lesions that progress from nonulcerated to ulcerated forms. Our goal was to characterize the immunological kinetics associated with this progression, comparing the cellular composition, cytokines and granzyme expression between lesions of patients with early (E-CL) and late stages (L-CL) of CL. Histopathological analysis showed that lesions from L-CL had more exuberant inflammatory infiltrate as compared to E-CL. Although E-CL and L-CL lesions were predominantly mononuclear, lesions from E-CL patients presented higher neutrophil and eosinophil counts than L-CL. While percentages of CD4⁺ and of CD68⁺ cells were slightly higher in L-CL, a fivefold increase of CD8 ⁺ cells was observed in L-CL, as compared to E-CL. Moreover, CD8⁺ T-cells from L-CL expressed significantly higher levels of granzyme A than E-CL. Interestingly, granzyme A expression was positively correlated with intensity of the inflammatory infiltrate in L-CL but not E-CL. Lastly, percentages of IFN-γ ⁺ and IL-10⁺ cells were higher in L-CL as compared to E-CL, with CD4⁺ T-cells and CD68⁺ monocytes as the main sources of these cytokines, respectively. These results suggest that recruitment of CD8⁺ granzyme A⁺ T cells is involved in lesion progression in human CL.     

CD8~+ T细胞在早期内毒素血症对心功能的损害作用

目的:探讨CD8+T细胞在早期内毒素血症心脏损伤中的浸润及其对心功能的影响。方法:野生雄性小鼠20只随机分为野生对照组和野生内毒素血症组,每组各10只;CD8敲除雄性小鼠10只,随机分为CD8敲除对照组和CD8敲除内毒素血症组,每组各5只。对照组均给予0.9%氯化钠液腹腔注射,内毒素血症组均给予脂多糖腹腔注射。6 h显微超声检测射血分数及短轴缩短分数;即刻处死并收取野生对照组及野生内毒素血症组各3只小鼠心脏组织,流式细胞技术检测心脏细胞悬液中巨噬细胞(F4/80+细胞)及CD8+T细胞、CD4+T细胞分布;其余小鼠心脏组织进行病理切片HE染色,观察心肌纤维断裂及炎症细胞浸润。结果:与野生对照组相比,野生内毒素血症组射血分数及短轴缩短分数显著降低(均为P<0.05);野生内毒素血症组F4/80+细胞、CD4+T细胞及CD8+T细胞均显著增加(均为P<0.05)。与野生内毒素血症组相比,CD8基因敲除内毒素血症组射血分数及短轴缩短分数均显著升高(均为P<0.05)。结论:急性内毒素血症导致心肌纤维损伤、心功能不全,心脏组织CD8+T等炎症细胞浸润;而缺乏CD8+T细胞时则减轻内毒素血症导致的心功能损伤,提示CD8+T细胞在急性内毒素血症诱导的心功能不全早期发挥重要作用。     

CD8+ T cells suppress autologous megakaryocyte apoptosis in idiopathic thrombocytopenic purpura

To investigate the effect and mechanism of the CD8⁺ T cells in bone marrow on autologous megakaryocytopoiesis in idiopathic thrombocytopenic purpura (ITP) patients, we prepared bone marrow mononuclear cells (MNCs) from 15 chronic ITP patients and 13 controls. MNCs were cultured in vitro directly (MNC group) or after depleting CD8⁺ T cells (CD8⁺ T-dep group) or adding purified autologous CD8⁺ T cells to CD8⁺ T-dep MNCs (Coculture group) or adding dexamethasone to the coculture (DEX group) all in semi-solid and liquid culture systems. The quantity and quality of megakaryocytes were measured. The megakaryocyte count was increased in the presence of autologous CD8⁺ T cells of patients with chronic ITP, while platelet production was reduced. In addition, lower percentages of polyploidy and apoptotic megakaryocytes, and higher levels of soluble Fas (sFas) in supernatant were observed. Dexamethasone successfully corrected this effect of CD8⁺ T cells on autologous megakaryocytopoiesis. These studies provide evidence that activated CD8⁺ T cells in bone marrow of patients with chronic ITP might suppress megakaryocyte apoptosis, leading to impaired platelet production. Megakaryocyte apoptosis would be a novel target for the management of ITP.     

Activated CD8+ T cells contribute to clearance of gastric Cryptosporidium muris infections

The role of CD4+ and CD8+ T lymphocytes in the development of a protective immune response against Cryptosporidium muris infection was studied by the reconstitution of severe combined immunodeficient (SCID) mice with well-defined populations of either naive or immune CD8+ or CD4+ T lymphocytes. Adoptive transfer of both naive and immune CD4+ T lymphocyte subpopulations protects SCID mice against cryptosporidiosis. Moreover, a significant biological impact of activated CD8+ T cells against gastric cryptosporidiosis was observed. The significant difference in the course and intensity of the infection in reconstituted SCID mice was found to be dependent on the protective function of both the CD4+ and CD8+ T-cell populations transferred. While SCID mice reconstituted with either immune or naive CD4+ or immune CD8+ T-cell subpopulations resolved the infection within 29, 37 and 51 days post-infection, respectively, those reconstituted with naive CD8+ T cells suffered from chronic infection similar to control SCID mice. Reconstitution with CD4+ T cells resulted in suppression of oocyst excretion and shortening of patent period in comparison with SCID mice reconstituted with CD8+ T cells. Thus, although CD4+ T cells are considered important in protective immunity, our results are the first to demonstrate the involvement of activated CD8+ T lymphocytes in the protection of mice against gastric cryptosporidiosis.     

CD8+ cytotoxic lymphocytes in cutaneous leishmaniasis

OBJECTIVE: Review of the literature on the role of CD8+ T cell in the immune response against Leishmania species that cause cutaneous leishmaniasis. The role of macrophages, dendritic cells, CD4 T cells and NK cells has been extensively analyzed in leishmaniasis, yet very little knowledge has been gained on CD8+ T cells in this disease. Murine models of leishmaniasis suggest that CD8+ T cells participate through IFNg production, yet their cytotoxic capacity may also play a crucial role, as has been found in human disease. It is an enigma what mechanisms underlie the CD8+ T cell activation. It is possible that dendritic cells activate CD8+ T cells through mechanisms that include antigen traspresentation. A better understanding of CD8+ T cells in the immune response against Leishmania will undoubtedly provide new insights into the physiopathogenesis of the disease that could lead to new therapeutic approaches against leishmaniasis.     

肺结核患者外周血CD_4~+、CD_8~+T细胞Blimp-1表达下降

目的研究活动性肺结核患者外周血单个核细胞(PBMCs)Blimp-1的表达及临床意义。方法采集31例活动期肺结核患者和45位健康对照组外周血,纯化PBMCs,用结核分枝杆菌ESAT-6和CFP-10混合性抗原肽库刺激,通过细胞表面标记和细胞内细胞因子染色技术,采用流式技术检测CD+4、CD+8T细胞Blimp-1的表达。结果与对照组比较,肺结核患者PBMCs中的CD+4、CD+8T细胞亚群分布出现显著性下降,且肺结核患者CD+4T细胞中Blimp-1的表达比例(%)下降(肺结核组89.5%(83.8%,95.7%),对照组94.5%(89.8%,98.7%),P0.05),且CD+4、CD+8T细胞中Blimp-1的表达量(平均荧光强度)也显著性下降(CD+4T细胞:肺结核组9.28(7.5,18.9),对照组15.4(11,25.4),P0.05);CD+8T细胞:肺结核组9.01(6.08,14.7),对照组14.2(9.53,23.1),P0.05)。结论活动期肺结核CD+4、CD+8T细胞群内Blimp-1的表达下降可能会使效应性和调节性T细胞的分化出现异常。Blimp-1可能参与结核病的疾病进程,这为研究结核病的诊断和治疗提供了线索。     

Microarray analysis reveals similarity between CD8+CD28- T cells from young and elderly persons, but not of CD8+CD28+ T cells

We isolated highly purified CD8⁺CD28⁺ and CD8⁺CD28⁻ T cell populations from healthy young and elderly persons for gene expression profiling using Affymetrix oligonucleotide microarrays. We demonstrate that the gene expression profile of CD8⁺CD28⁻ T cells is very similar in young and elderly persons. In contrast, CD8⁺CD28⁺ in elderly differ from CD8⁺CD28⁺ in young persons. Hierarchical clustering revealed that CD8⁺CD28⁺ in elderly are located between CD8⁺CD28⁺ in young and CD8⁺CD28⁻ (young and old) T cells regarding their differentiation state. Our study demonstrates a dichotomy of gene expression levels between CD8⁺CD28⁺ T cells in young and elderly persons but a similarity between CD8⁺CD28⁻ T cells in young and elderly persons. As CD8⁺CD28⁺ T cells from elderly and young persons are distinct due to a different composition of the population, these results suggest that the gene expression profile does not depend on chronological age but depends on the differentiation state of the individual cell types.     

Protective and pathogenic roles of CD8+ T cells during malaria infection

CD8+ T cells play a key role in protection against pre-erythrocytic stages of malaria infection. Many vaccine strategies are based on the idea of inducing a strong infection-blocking CD8+ T cell response. Here, we summarize what is known about the development, specificity and protective effect of malaria-specific CD8+ T cells and report on recent developments in the field. Although work in mouse models continues to make progress in our understanding of the basic biology of these cells, many questions remain to be answered - particularly on the roles of these cells in human infections. Increasing evidence is also emerging of a harmful role for CD8+ T cells in the pathology of cerebral malaria in rodent systems. Once again, the relevance of these results to human disease is one of the primary questions facing workers in this field.     

CD8 and CD4 T Cells in West Nile Virus Immunity and Pathogenesis

CD4 and CD8 T lymphocytes are adaptive immune cells that play a key role in the immune response to pathogens. They have been extensively studied in a variety of model systems and the mechanisms by which they function are well described. However, the responses by these cell types vary widely from pathogen to pathogen. In this review, we will discuss the role of CD8 and CD4 T cells in the immune response to West Nile virus infection.     

Decreased numbers of signal-joint T cell receptor excision circle-containing CD4+ and CD8+ cells in systemic lupus erythematosus patients

Systemic lupus erythematosus (SLE) patients have a decreased number of peripheral blood T cells containing signal-joint T cell receptor excision circles (Sj TRECs), which are considered an indicator of thymic output. The objective of this study was to investigate the mechanism of the decrease in such T cells. Peripheral blood T cells from SLE patients were classified into CD4+ and CD8+ cells. Sj TREC levels were measured by real-time PCR. Telomerase activity was determined by the telomeric repeat amplification protocol assay. The numbers of Sj TREC containing CD4+ and CD8+ cells were lower in the peripheral blood of SLE patients than in the controls. A correlation was found between the numbers of Sj TREC-positive CD4+ and CD8+ cells. The level of TRECs is influenced by an increase in cell division. To examine this increase, telomerase activity as an indicator of cell division was measured simultaneously; however, there was no correlation between the Sj TREC level and telomerase activity. These results suggest that decreased thymic output occurs in SLE patients.     

Purification of cytomegalovirus-specific CD8 T cells from peripheral blood using HLA–peptide tetramers

Cytomegalovirus (CMV) reactivation and disease remains an important clinical problem for patients after allogeneic stem cell transplantation. Impaired cellular immune control of viral replication is responsible for viral reactivation, and transfer of CMV-specific T cells from transplant donors can be effective in providing protection. Recent reports have indicated that the frequency of CMV-specific CD8(+) T cells in the peripheral blood of healthy donors is surprisingly high. Here we demonstrate that by using a combination of human leucocyte antigen (HLA) Class I-peptide tetramers and magnetic selection it is possible to select CMV-specific T cells from CMV antibody-positive individuals to high purity. Reliable purification of CMV-specific T cells up to 99.8% of CD8(+) cells was possible within hours, even when starting with a precursor frequency of < 0.1% of peripheral blood CD8(+) T cells. CMV-specific T cells remained functional after the selection process. This novel form of antigen-specific T-cell selection should facilitate the selection of T cells for cellular immunotherapy to treat or prevent CMV disease after transplantation. In addition, this technique could potentially be applied to many antigens including against other infective agents and tumour-specific antigens.     

Demonstration of strain-specific CD8 T cell responses to Theileria annulata

The present study set out to examine the nature and specificity of the bovine CD8 T cell response at the clonal level in a group of eight animals immunized with a cloned population of Theileria annulata . The results demonstrated that immunized animals generated parasite-specific CD8 T cells that produced IFNγ in response to parasite stimulation but had highly variable levels of cytotoxicity for parasitized cells. The study also demonstrated that these parasite-specific CD8 T cells could be propagated and cloned in vitro from the memory T cell pool of cattle immunized with live T. annulata parasites. Within the small group of animals studied, there was evidence that responses were preferentially directed to antigens presented by an A10⁺ class I major histocompatibility complex (MHC) haplotype, suggesting that responses restricted by products of this haplotype may be dominant. The A10-restricted responses showed differential recognition of different parasite isolates and clones. By using a cloned population of parasites both for immunization of the animals and for in vitro analyses of the responses, we obtained unambiguous evidence that at least a proportion of CD8 T cells restricted by one MHC haplotype were parasite strain restricted.     

Idiotype-pulsed dendritic cells are able to induce antitumoral cytotoxic CD8 cells in chronic lymphocytic leukaemia

Idiotypic structures of immunoglobulins from malignant B cells constitute tumour-specific antigens, though the function of immunoglobulin-specific CD8+ T cells in disease control and rejection remains unclear. We have studied five cases of B chronic lymphocytic leukaemia patients affected with indolent (three patients) or aggressive (two patients) disease. We showed that CD8+ T cells with major histocompatibility complex class I-restricted cytotoxicity against autologous tumour B cells could be generated following repeated stimulations with idiotype-pulsed dendritic cells in vitro. CD8+ T-cell lines were able to upregulate CD69 expression and to release interferon (IFN)-gamma upon contact with the autologous B cells, though cytolytic activity was only substantiated for patients with indolent disease. The failure of cytolytic activity in patients with aggressive disease may be explained by a skewed maturation of memory CD8 cells.     

CD48在类风湿关节炎患者外周血CD8+T细胞上的表达及意义

目的探讨类风湿关节炎（RA）患者CD8^＋T细胞上CIM8的表达及意义。方法选择30例RA患者（RA组）和30名健康人（对照组），采用流式细胞仪测定两组外周血CD8^＋T细胞表面上CD48的平均荧光强度，分析RA患者CD48在CD8^＋T细胞上表达的临床意义。结果RA组CD48^＋CD8^＋T细胞表面平均荧光强度明显低于正常对照组，差异有统计学意义（P〈0．01）。而两组CD48^＋CD4^＋T细胞的表面平均荧光强度差异无统计学意义。结论RA患者CD8^＋T细胞上CD48的表达低于对照组，CD48的表达减低使抑制性T细胞减少可能在RA的发病过程中起作用。     

CD4+ T cells in lung tissue predict responsiveness to cyclosporin A in interstitial pneumonia

OBJECTIVE: A limited number of case studies have demonstrated the steroid-sparing and disease stabilization effects of cyclosporin A (CsA) combined with corticosteroid in patients with chronic interstitial pneumonia (IP). Although CsA is known to inhibit the proliferation and function of CD4+ T cells, it is not clear what type of IP is responsive to CsA administration. METHODOLOGY: In order to evaluate whether any lymphocyte subsets in alveolar tissue predict the responsiveness to CsA, morphometric analysis was performed on lung tissue obtained from six IP patients who were treated with a combination of CsA and steroid because the therapeutic effect of steroid alone had been limited. RESULTS: Cell densities of CD4+ T cells were significantly decreased in the alveolar tissues obtained from CsA responders (n = 3) compared to non-responders (n = 3) (120 +/- 86/mm2 vs 503 +/- 172/mm2, P=0.0495). CD4/CD8 ratios of CsA responders were also significantly lower than those of non-responders (0.315 +/- 0.070 vs 1.975 +/- 0.965, P=0.0463). However, cell densities of CD8+ T cell and areas of B cells aggregates were similar in both groups. CONCLUSIONS: The present observations, contrary to expectation, reveal that lower cell densities of CD4+ T cells and lower CD4/CD8 ratios are associated with responsiveness to CsA in combination therapy, suggesting that pharmacological actions other than suppression of CD4+ T cells explain the efficacy of CsA in patients with chronic IP.     

肝细胞癌患者 Treg 细胞对 CD8＋T 淋巴细胞穿孔素表达的影响

目的：研究肝细胞癌患者免疫抑制性 Treg 细胞对 CD8＋ T 淋巴细胞穿孔素表达的影响。方法采集20例肝细胞癌患者和20名健康人的外周血,用流式分析法检测抗-CD3／CD28刺激48 h 后 CD8＋ T 淋巴细胞的穿孔素表达情况。免疫磁珠分离法分离健康人 CD8＋ T 淋巴细胞和肝细胞癌患者 Treg 细胞,一组 CD8＋ T 淋巴细胞单独培养,另一组CD8＋T 淋巴细胞与 Treg 细胞共同培养,用流式细胞法检测抗-CD3／CD28刺激48 h 后两组 CD8＋ T 淋巴细胞穿孔素表达情况。结果肝细胞癌患者外周血中 CD8＋ T 淋巴细胞穿孔素表达量与健康人相近,分别为（10．74±3．96）％和（12．6±2．48）％,差异无统计学意义（P ＞0．05）。CD8＋ T 淋巴细胞单独培养和与肝癌患者 Treg 细胞共培养后,健康人 CD8＋ T 淋巴细胞穿孔素表达量分别为（34．2±3．65）％和（20．43±4．52）％,差异有统计学意义（t＝11．42,P ＜0．01）。结论肝癌患者免疫抑制性 Treg 细胞可使 CD8＋ T 淋巴细胞穿孔素表达量降低。