Bovine helper T-cell clones specific for lymphocytes infected with Theileria parva (Muguga)

T-cell clones specific for lymphocytes infected with Theileria parva were derived from animals immunized by infection with T. parva (Muguga). These clones were non-cytolytic and had the BoT4+ BoT8- surface phenotype, BoT4 and BoT8 being the bovine analogues of human CD4 and CD8 molecules. The clones proliferated in response to irradiated autologous lymphoblasts infected with T. parva (Muguga) but not to autologous uninfected lymphoblasts or monocytes. They were parasite strain-specific, in that they did not respond to autologous lymphoblasts infected with another parasite stock, T. parva (Marikebuni). The clones proliferated in the absence of exogenous T-cell growth factor (TCGF) and produced TCGF when stimulated with concanavalin A. Induction of proliferation of the cloned T-cells was genetically restricted, and evidence was obtained which indicated that they were restricted by determinants on class II major histocompatibility complex (MHC) molecules. These findings demonstrate that infections with T. parva stimulate antigen-specific MHC-restricted T-cells with the properties of T-helper cells. The results also provide further evidence for the expression of a parasite strain-specific antigen on the surface of T. parva-infected lymphocytes.     

Theileria parva (Muguga) infects bovine T-lymphocytes in vivo and induces coexpression of BoT4 and BoT8

During the course of a lethal infection with Theileria parva (Muguga), the surface phenotypes of efferent lymphatic lymphocytes (ELL) were analysed to determine whether the parasite preferentially infected any particular subpopulation of cells. In the second week of infection, when the proportion of lymphoblasts and parasitized cells increased to 50% of the total ELL, greater than 99% of infected cells expressed T-lymphocyte markers including both BoT4 and BoT8. From day 10, a population of T-lymphocytes coexpressing BoT4 and BoT8 appeared in ELL, reaching 33% by day 14. Similar changes were observed in peripheral blood mononuclear cells (PBM) and lymph node cells (LNC). Analysis of ELL sorted into populations differing on the basis of expression of BoT4 and BoT8, revealed a higher level of parasitosis in the BoT4+ and BoT8+ lymphocytes than in the BoT4+ BoT8- or BoT4- BoT8+ populations. For comparison, the phenotypes of 28 cloned cell lines, obtained by infection of PBM with sporozoites in vitro, were examined. All of these clones exhibited T-cell markers. Nine of the clones expressed both BoT4 and BoT8; within each of these lines, BoT4 was expressed on all cells, whereas BoT8 was expressed at variable concentrations on 20-70% of cells. That BoT4+ cells were induced by T.parva (Muguga) to coexpress BoT8 was demonstrated directly by the finding that a BoT4+ BoT8- T-cell clone expressed BoT8 following infection with the parasite.     

Induction of lymphokine-activated cytotoxic T lymphocytes stimulated by dendritic cells and autologous tumor from a patient with gastric cancer and their effects in vitro

BACKGROUND/AIMS: The purpose of the study was to generate lymphokine-activated cytotoxic T lymphocytes stimulated by dendritic cells (DC) and autologous tumor from a patient with gastric cancer and to clarify their cytotoxic effects in vitro. METHODOLOGY: DC was induced by interleukin-4 (IL-4) and granulocyte-macrophage-colony-stimulating factor (GM-CSF) from the peripheral blood mononuclear cells (PBMC). Then, PBMC was incubated with mitomycin C-treated tumor cells and DC, and following that was activated with IL-2 and anti-CD3. Induction of DC and cytotoxic T cells (CTL) were confirmed by the analyses of the cell surface antigens, killing activities, and blocking tests. RESULTS: Induction of DC and cytotoxic T cells (CTL) was confirmed by the analyses of the cell surface antigens, killing activities, and blocking tests. In vitro study demonstrated that lymphokine-activated lymphocytes pulsed by DCs and autologous tumor contained the largest population of CTLs, the greatest production of IFN-gamma, and the greatest ATK activity. CONCLUSIONS: Those results indicated that CTLs could be generated in vitro from a patient with gastric cancer more successfully by this method than by conventional methods, suggesting the possibility of a new immunotherapy for the treatment of gastric cancer.     

Adoptive transfer of immunity to Theileria parva in the CD8+ fraction of responding efferent lymph.

Evidence that class I major histocompatibility complex-restricted cytotoxic T lymphocytes (CTL) are involved in immunity to malaria has highlighted the potential importance of these cells in protection against intracellular parasites. Parasite-specific CTL are a prominent feature of the immune response of cattle to Theileria parva, a related apicomplexan parasite. The relationship between the appearance of these cells in the blood of immune cattle under challenge and the clearance of infection suggests that they are involved in the control of infection, but direct evidence is lacking that CTL can mediate protection. We have made a quantitative kinetic study of CTL responses in lymph originating from infected lymph nodes in a number of immune cattle under challenge with T. parva. Direct killing activity and the frequency of CTL precursors (CTLp) within responding cell populations were evaluated. A substantial increase in the proportion of CD8+ CTL was observed between days 8 and 11 after challenge. Frequencies of CTLp as high as 1:32 were observed and activity was essentially confined to the large blasting cell fraction. The analogous response in peripheral blood was of lower magnitude and delayed by 1-2 days. The high frequency of CTLp in efferent lymph permitted the adoptive transfer of this activity between immune and naive monozygotic twin calves. In separate experiments, naive calves lethally infected with T. parva were protected by inoculation of up to 10(10) responding CD8+ T cells derived from their immune twins. Elimination of CD8+ T cells within the inoculum abrogated this effect. These findings provide direct evidence that CD8+ T cells can control T. parva infections in immune cattle.     

HLA-C and HLA-E reduce antibody-dependent natural killer cell-mediated cytotoxicity of HIV-infected primary T cell blasts

OBJECTIVE: To determine whether the presence of HLA-C and HLA-E on HIV-infected cells modulates autologous natural killer (NK) cells from implementing antibody-dependent cell-mediated cytotoxicity (ADCC) of HIV-infected cells. DESIGN: The capability of HLA-C and HLA-E to control NK cell killing of HIV-infected autologous T cells coated with anti-gp120 monoclonal antibody was determined by blocking the interaction between the inhibitory receptors on NK cells and the MHC class I molecules on infected cells. METHODS: Phytohemagglutinin-treated CD4 T cells were infected in vitro with HIV-1. Infected cells were separated from uninfected cells by removal of CD4 T cells. Infected cells were labeled with chromium-51, treated with a cocktail of four different monoclonal antibodies against HIV gp120, and co-cultured with freshly isolated autologous NK cells that were incubated with or without anti-CD159a, anti-CD158a, and CD158b, or all three antibodies combined. Killing of the HIV-infected cells by NK cells was assessed in a 4 h cytotoxic assay. RESULTS: When the interaction between NK cell inhibitory receptors (i.e., CD158a, CD158b, and CD159a) and MHC class I molecules (i.e., HLA-C and HLA-E) on HIV-infected autologous T cells was blocked, a drastic increase in killing of anti-gp120-coated HIV-infected cells by NK cells was observed. CONCLUSION: These studies indicate that the presence of HLA-C and HLA-E molecules on HIV-infected cells may facilitate evasion of NK-mediated killing of antibody-coated HIV-infected cells.     

Expansion of autorecognitive cytotoxic effectors in human cancer by T cell growth factor (Interleukin 2)1

Conditions for the production of supernates from mitogen stimulated human lymphocytes with the capacity to induce proliferation in long term MLC or PHA stimulated cultures which no longer respond to PHA have been investigated. These supernates can be used to maintain lymphocytes in continuous growth with a doubling time of approximately 48 hours. Cells grown from MLC stimulated cultures show less than 80% SRBC rosetting cells, are Fc-, do not show ADCC activity and induce reduced lysis of K562 compared with freshly isolated effectors. Cultured T cells (CTC) show high lytic activity against the inducing PHA blasts but not autologous or third part targets. Similar experiments have been performed with lymphocytes from the blood, lymph node, spleen and tumour of cancer patients and CTC tested for cytotoxicity against autologous and allogeneic tumour cells and the K562 compared with freshly isolated effectors. Cultured T cells (CTC) show high lytic activity against the inducing PHA blasts but not autologous or third part targets. Similar experiments have been performed with lymphocytes from the blood, lymph node, spleen and tumour of cancer patients and CTC tested for cytotoxicity against autologous and allogeneic tumour cells and the K562 cell line. Cytotoxicity for autologous tumour was found in all samples. This was accompanied by killing of allogeneic cells in most instances but killing of K562 was only rarely demonstrable. These data would be consistent with a polyclonal expansion of cytotoxic effectors in the samples. The finding of autologous reactivity suggests the presence of autorecognitive cytotoxic T cells in cancer patients with specificity for tumour. Cloning experiments are currently in progress to investigate this possibility further.     

Generation and characterization of ex vivo propagated autologous CD8+ cells used for adoptive immunotherapy of patients infected with human immunodeficiency virus

Cytolytic T lymphocytes play an important role in host defense against viral infections, including human immunodeficiency virus (HIV). In a phase I clinical trial (protocol 080 of the AIDS Clinical Trials Group), generation of CD8+ effector cells from peripheral blood of patients with acquired immunodeficiency syndrome (AIDS)-related complex (ARC) or AIDS and safety of autologous adoptive transfer of these cells were evaluated. For therapeutic infusions, CD8+ T cells were purified by positive selection on anti-CD8 monoclonal antibody-coated flasks from leukapheresed peripheral blood of seven patients. These CD8+ T cells were cultured in the presence of interleukin-2 and phytohemagglutinin for up to 3 weeks to obtain cells sufficient for therapeutic infusions (10(8) to 10(10)). All 31 cell cultures established from the seven patients and used for therapy were highly enriched in CD8+ (mean, 97%), CD8+HLA-DR+ (50%), cytotoxic CD8+CD11b- (82%), and memory CD29+ (78%) T lymphocytes. In vitro expanded CD8+ cells had excellent cytotoxic function at the time they were used for therapy, including HIV-specific activity against autologous targets infected with vaccinia vectors expressing HIV-IIIb antigens, gag, pol, and env. Anti-HIV activity of cultured CD8+ cells was significantly higher than that of autologous fresh peripheral blood lymphocytes. Our results show that CD8+ T lymphocytes obtained from peripheral blood of symptomatic HIV-infected patients can be purified, cultured to obtain large numbers of cells with enhanced anti-HIV activity, and safely infused into patients with AIDS as a form of immunotherapy.     

Varicella-zoster virus-specific HLA-restricted cytotoxicity of normal immune adult lymphocytes after in vitro stimulation

Varicella-zoster virus (VZV)-specific cytotoxic T cell responses were studied in 35 presumably immune and two nonimmune adult donors and in two patients with herpes zoster. Peripheral blood lymphocytes (PBLs) were stimulated for five or 12 days with autologous, irradiated, VZV-infected PBLs. Cytotoxicity was measured in a chromium-release assay. Target cells were usually cryopreserved, phytohemagglutinin-stimulated PBLs, either infected with VZV or uninfected. In testing the presumably immune adults, VZV-specific cytotoxicity was observed in 32 (91%) of 35 cases after five days and in 19 (90%) of 21 cases after 12 d of stimulation. Lysis of HLA-matched target cells was significantly greater than that of mismatched, VZV-infected target cells after both intervals. Responses were similar when PBLs from two patients with acute zoster were tested after in vitro stimulation and in one of those two tested without in vitro stimulation.     

Studies on Theileriidae (Sporozoa) in Tanzania. VIII. Experiments with African buffalo (Syncerus caffer).

It has been found that African buffalo may remain infective carriers of Theileria parva lawrencei for at least 5 years. This infection is now known to exist in buffalo in 3 sites in northern Tanzania. It was shown that buffalo can be infected with Haematoxenus veliferus and Theileria mutans of cattle and retransmission of these parasites from buffalo to cattle was successful. The species of Haematoxemus reported in wild buffalo in central and East Africa is likely to be H. veliferus, while the possibility that Theileria barnetti of buffalo is identical with T. mutans should be considered. African buffalo can also be infected with Babesia bigemina and Anaplasma marginale of cattle and although the infections are latent, their blood may remain infective for at least several months.     

Malignant plasma cells are sensitive to LAK cell lysis: pre-clinical and clinical studies of interleukin 2 in the treatment of multiple myeloma

To assess the role of the cytokine interleukin 2 (IL2) in the treatment of patients with multiple myeloma, we examined the sensitivity of plasma cell lines and malignant plasma cells from multiple myeloma (MM) patients to cell and cytokine-mediated killing induced by IL2. Unstimulated peripheral blood mononuclear cells (PBM) from normal donors produced little killing (mean lysis 1.0 +/- 1.0%, effector:target (ET) ratio 50:1), but cytotoxicity was modestly increased when PBM were incubated with IL2 prior to assay (8.0 +/- 2.9%). Unstimulated PBM from patients with MM also failed to kill autologous malignant plasma cells (mean 0.6 +/- 0.6%), but after exposure to IL2 they induced substantial lysis of autologous malignant cells (mean 55.3 +/- 22.1%). In addition, tumour necrosis factor (TNF) and interferon-gamma (IFN-gamma), two cytokines released from mononuclear cells in response to IL2, also reduced the survival and thymidine uptake of malignant plasma cells in culture. To determine whether these potentially beneficial immunomodulatory effects could be reproduced by in vivo administration of IL2, we have administered seven courses of IL2 to four patients with MM after autologous bone marrow transplant (ABMT). No serious adverse effects were noted. Increases in natural killer (NK) and lymphokine-activated killer (LAK) activity of PBM occurred during IL2 infusion, although cells capable of killing autologous MM cells did not circulate. However, IL2 infusions also induced substantial increases in the production of the cytokines TNF and IFN-gamma from peripheral blood lymphocytes. These results suggest that the in vivo administration of IL2 in MM deserves further evaluation, particularly for its potential to control minimal residual disease.     

Theileria parva and the bovine CTL response: down but not out?

Theileria parva is a tick-borne intracellular protozoan of cattle, with obligate sequential differentiation stages in lymphocytes and erythrocytes. Immunity is mediated by cytotoxic T lymphocytes (CTL) that target and clear parasitized lymphocytes but allow persistence of infected erythrocytes, which are required for transmission to the tick. The life cycle of T. parva is haploid with the exception of a brief diploid stage in the tick vector during which sexual recombination occurs. There is evidence for antigenic diversity in field parasite populations, although broad immunity can be acquired following exposure to a limited number of strains. The CTL response in individual animals is tightly focused and its specificity is strongly influenced by major histocompatibility complex (MHC) phenotype. This review discusses the issue of how CTL immunity is likely to impact on parasite population structure in the light of available information on diversity of the parasite and its ability to recombine.     

Cytotoxic factors secreted by cells infected by human immunodeficiency virus type I

Conditioned media from human immunodeficiency virus type I (HIV-1) infected cells were tested for cytotoxic cell-derived factors. The assay used a murine fibroblast cell line which is sensitive to the effects of tumor necrosis factors, but nonpermissive for HIV-1 replication. Cytotoxic activity was detected in cultures of peripheral blood mononuclear cells infected with HIV-1. However, no differences in activity were found in conditioned media from infected lymphoid or monocytoid cell lines compared to their uninfected counterparts. These data suggest that cytotoxic activities of this type are not mediators of cell killing resulting from HIV-1 infection. Thus, this cytotoxic activity is a direct or indirect result of virus replication or cytopathicity. One should consider a role for this cytotoxic factor, secreted by HIV-1 infected mononuclear cells, in various aspects of infection in vivo, such as AIDS encephalopathy or the systemic manifestations accompanying ARC.     

Cytotoxic T-cells elicited in cattle challenged with Theileria parva (Muguga): evidence for restriction by class I MHC determinants and parasite strain specificity

The MHC restriction and parasite strain specificity of cytotoxic cells elicited in a group of Theileria parva (Muguga)-immunized cattle following homologous challenge, were investigated. The cytotoxic cells were specific for parasitized target cells and in 9 of the 10 animals examined, they were clearly genetically restricted. Cytotoxicity could be inhibited by monoclonal antibodies (MoAb) to class I MHC molecules but not by MoAb to class II molecules, indicating that a large component of the response was restricted by class I MHC determinants. Low levels of inhibition of cytotoxicity were also obtained with a MoAb to the T-cell subset marker BoT8, suggesting that at least part of the response was mediated by BoT8+ lymphocytes. When cytotoxic cells from individual cattle were assayed on panels of parasitized target cells, there was a close correlation between susceptibility of the target cells to lysis and sharing of BoLA-A locus-encoded specificities with the effectors. This observation, taken together with the knowledge that within several of the sets of BoLA-A-matched targets the relevant BoLA-A specificities were on different MHC haplotypes, indicated that the responses were restricted predominantly by BoLA-A products. In individual cattle there was a striking bias in the restriction of the response to one or other BoLA-A specificity. Among the six specificities represented, responses restricted by w6, w8 and KN18 consistently predominated over responses restricted by w7, w10 and w11. In the three cattle tested for parasite strain specificity, two showed complete specificity and one partial specificity for cells infected with the parasite stock used for immunization, T. parva (Muguga).     

Nitric oxide inhibits establishment of macroschizont-infected cell lines and is produced by macrophages of calves undergoing bovine tropical theileriosis or East Coast fever

Nitric oxide (NO) was produced when bovine peripheral blood mononuclear cells (PBMC) or purified, adherent PBMC (macrophages) were incubated in vitro with bovine recombinant interferon gamma (Bo rIFN-γ). NO was produced by cells from naive, uninfected calves as well as by cells from cattle either infected with or recovered from infection with Theileria annulata or Theileria parva. PBMC of cattle undergoing tropical theileriosis (T. annulata infection) or East Coast fever (T. parva infection) synthesized NO spontaneously in vitro. NO was also induced when PBMC of immune, but not of naive, cattle were cultured with T. annulata macroschizont-infected cell lines. Macrophages alone were not stimulated to produce NO by such infected cells. In vitro establishment of macroschizont-infected cell lines was suppressed either by incubating sporozoites with S-nitroso-N-acetyl-DL-penicillamine (SNAP), a NO releasing molecule, prior to invasion of PBMC or by pulsing developing cultures of trophozoite-infected cells with SNAP. Proliferation of established macroschizont-infected cell lines was not affected by SNAP. Taken together with the well documented roles of NO in neurotransmission, vasodilatation, cell and tissue damage and immunosuppression, the results presented here indicate that NO may not only protect cattle against T. annulata and T. parva but, if produced in excess, play a prominent role in the pathogenesis of tropical theileriosis and East Coast fever.     

TCR gamma delta bearing lymphocyte clones with lymphokine-activated killer activity against autologous leukemic cells

Activated T lymphocytes with the T-cell receptor (TCR) gamma delta (CD3+ and TCR delta 1+) exhibit strong cytotoxic activity against the standard natural killer (NK) and lymphokine-activated killer (LAK) sensitive target cells. In order to test the cytotoxic activity of gamma delta T lymphocytes against autologous leukemic cells, 84 clones of gamma delta T lymphocytes were obtained from the peripheral blood of three acute lymphoblastic leukemia (ALL) patients. Forty-four of these T-cell clones were active against an LAK-sensitive cell line and the other 40 were active against K562, an NK target cell line. In each of the three patients, cytotoxic clones against autologous leukemic cells were obtained. Among the 84 clones, ten were able to kill autologous tumor cells, including eight that lyse the LAK-sensitive target and two with NK activity. The clones were highly cytotoxic, stable, and easily expanded in large quantity.     

Induction of cytomegalovirus-specific CD4+ cytotoxic T lymphocytes from seropositive or negative healthy subjects or stem cell transplant recipients

OBJECTIVE: We generated cytomegalovirus (CMV)-specific cytotoxic T lymphocytes (CTL) in vitro using dendritic cells (DC) pulsed with crude CMV antigens (Ag). PATIENTS AND METHODS: Mononuclear cells from healthy CMV-seropositive or seronegative volunteers and from stem cell transplant (SCT) recipients were cultured with CD14(+) monocyte-derived DC prepulsed with CMV Ag and then matured in vitro with lipopolysaccharide and tumor necrosis factor-alpha. After proliferation, cells were checked for phenotype (CD4/CD8), while killing activity was measured by 51Cr-release assay. RESULTS: CD4(+) T cells, the main proliferating cells from both seropositive and seronegative individuals, killed autologous Ag-pulsed DC but not vehicle-pulsed autologous DC or CMV-pulsed allogeneic DC. Similar CTL induction was accomplished from SCT recipients. Significant killing of autologous CMV-infected fibroblasts required 16-hour incubation as opposed to the standard 4-hour incubation, which was prevented by either a perforin inhibitor or anti-Fas ligand monoclonal antibody. CTL enhanced surface HLA-DR expression of CMV-infected fibroblasts, and their activity was neutralized by anti-HLA-DR monoclonal antibody. CONCLUSION: CMV-specific CD4(+) CTL were inducible with or without antiviral humoral immunity, even from immunosuppressed SCT recipients. These CTL showed perforin- and Fas/Fas ligand-mediated cytotoxicity after long-term (16-hour) contact with CMV-infected targets.     

Antigen-specific recognition of autologous leukemia cells and allogeneic class-I MHC antigens by IL-2-activated cytotoxic T cells from a patient with acute T-cell leukemia

Culturing of leukemic blood lymphocytes from a patient with acute T-cell lymphoblastic leukemia (T-ALL) with interleukin-2 (IL-2) yielded T-cell line AK-1 with a remarkable cytotoxic specificity. This line mediated strong lysis of tumor target lines expressing major histocompatibility complex (MHC) class I antigens, such as Raji, CEM, and Molt-4 cells, but no killing of K562 and Daudi cells, which are deficient in MHC class I. In contrast, lymphokine-activated killer (LAK) cells from normal donors destroyed all these tumor targets, without MHC restriction. Line AK-1, originating from residual normal T cells present in the leukemic blood, lysed autologous leukemic blasts and peripheral blood lymphocytes (PBL) from many but not all allogeneic individuals but failed to kill autologous remission lymphocytes. Destruction of the autologous leukemic targets by AK-1 could be inhibited by unlabeled competitor target cells that were lysed by AK-1, but not by target cells that were not lysed. This suggests that AK-1 specifically recognized an alien determinant on the autologous ALL cells, crossreactive with allogeneic MHC class I antigens. This reactivity with some degree of tumor specificity may be a leukemic equivalent to responses reported for populations of tumor infiltrating lymphocytes (TIL) seen in some solid tumors.     

Induction by specific T lymphocytes of intracellular destruction of Leishmania major in infected murine macrophages

The following cell populations derived from lymph nodes of mice primed in vivo with living Leishmania major promastigotes were tested for their capacity to induce parasiticidal activity in L. major-infected macrophages: a L. major-primed lymph node cells, draining lymph node cells from mice primed by a subcutaneous injection of living L. major in Freund's Complete Adjuvant; b L. major-specific T blasts, i.e. blast T cells resulting from in vitro challenge of primed lymph node cells with L. major, c propagated L. major specific T blasts, i.e. blast T cells after propagation in vitro in antigen-free medium containing interleukin-2. Results indicate that cocultivation of these L. major specific lymphocyte populations with infected peritoneal exudate macrophages induced progressive destruction of intracellular L. major. This effect was antigen specific since similar populations obtained from mice primed either with ovalbumin or bovine serum albumin did not induce significant parasite killing. The various lymphocyte populations examined did not express cytolytic activity for syngeneic macrophages infected with L. major when tested in a short-term 51Cr release assay. These negative results could not be attributed to an inability of infected macrophages to be lysed by cytolytic lymphocytes since cytolytic T lymphocytes directed to H-2 alloantigens present on macrophages were perfectly capable of lysing these infected macrophages as revealed in a 4 h 51Cr release assay. Interestingly, infected macrophages from either BALB/c (H-2d), NZB (H-2d) or CBA (H-2k) mice were lysed by cytolytic T lymphocytes specific for their respective H-2 alloantigens as well as uninfected macrophages. These results suggest that H-2 expression on the surface of infected macrophages from either L. major susceptible or resistant mouse strains is sufficient to be detected by allogeneic cytolytic T lymphocytes.     

Induction of specific cytolytic T lymphocytes using fusions of hepatocellular carcinoma (HCC) patient-derived dendritic cells and allogeneic HCC cell line

BACKGROUND/AIMS: To assess the ability of hepatocellular carcinoma (HCC) patient-derived dendritic cells (DCs) fused with allogeneic HCC cell line to activate autologous lymphocytes to generate specific cytotoxic T lymphocytes (CTL) in vitro. METHODOLOGY: DCs were obtained by culturing adherent peripheral blood mononuclear cells (PBMC) from HCC patients in the presence of 100 microg/L recombinant human granulocyte/ macrophage- colony stimulating factor (rhGM-CSF) and 20 microg/L interleukin-4 (rhIL-4) for 1 week in vitro. DCs were fused with allogeneic HCC cell line HepG2 cells using polythyleneglycol (PEG), and the fusion cells were designated as DCs/HepG2. By labeling DCs and HepG2 with green and red fluoresceins, respectively, the cellular fusion was examined under fluorescence microscope. The ability of DCs/HepG2 to stimulate proliferation and differentiation of autologous lymphocytes was assessed by MTT method, and the specific killing efficacy of DCs/HepG2-induced CTL against HepG2 was evaluated. RESULTS: HCC patient-derived DCs expressed a certain level of CD1a, HLA-DR, CD54, CD80 and CD86. Fluorescence microscopic examination demonstrated that co-incubation of DCs and HepG2 in the presence of PEG lead to generation of DCs/HepG2. In the mixed lymphocyte reaction assay, DCs/HepG2 had a significantly greater ability to activate proliferation of autologous lymphocytes, as compared with DCs alone, DCs plus HepG2, HepG2 alone and medium control (P<0.05). The DCs/HepG2-activated CTL showed a potent specific killing efficacy against HepG2 cells. CONCLUSIONS: Fusions of HCC patient-derived DCs and allogeneic HCC cell line could efficiently stimulate autologous lymphocytes to generate tumor-specific CTL in vitro. It might represent a promising approach of immunotherapy for HCC.     

Mechanisms of immunosuppression in cytomegalovirus mononucleosis. II. Virus-monocyte interactions

Virus-monocyte interactions were evaluated in patients with mononucleosis due to cytomegalovirus (CMV). Group 1 patients studied about two weeks after the onset of symptoms had lymphocyte responses to concanavalin A (con A) that were maximally suppressed and unaffected by in vitro culture or reconstitution with monocytes. Lymphocytes from group 2 patients studied about three weeks after the onset of symptoms had less markedly suppressed responses, which were reversed by in vitro culture or by reconstitution with monocytes. Monocyte depletion resulted in a marked diminution of fresh lymphocyte responses of group 2 patients but not of group 1 patients. CMV was isolated from blood monocytes of four patients with mononucleosis; intact, infected monocytes were capable of suppressing responses of cultured autologous lymphocytes to con A. Monocytes from uninfected control donors were infected in vitro with CMV and evaluated for the induction of suppressor activity. CMV-infected monocytes were significantly more suppressive for autologous lymphocyte responses to con A than were uninfected monocytes.