Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “CTL”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 757 records · Page 42Linked to original sources
PubMed2004

Identification of HLA-A2-restricted CTL epitope encoded by the MAGE-n gene of human hepatocellular carcinoma.

BACKGROUND: Identification of the cytotoxic T lymphocytes (CTL) restricted epitopes of tumor antigens opens up possibilities of developing a new cancer vaccine. For the MAGE-n has been demonstrated closely associated with hepatocellular carcinoma (HCC) and HLA-A2.1 is found in over 50% of HCC patients in China, we aim at identifying MAGE-n-encoded peptide presented by HLA-A2.1. MATERIALS: A HLA-A2.1-restricted CTL epitope was identified by using an improved "reverse immunology" strategy: (a) computer-based epitope prediction from the amino acid sequence of MAGE-n antigen; (b) peptide-binding assay to determine the affinity of the predicted peptide with HLA-A2.1 molecule; (c) stimulation of primary T-cell response against the predicted peptides in vitro; and (d) testing of the induced CTLs toward HCC cells expressing MAGE-n antigen and HLA-A2.1. RESULTS: Of the five tested peptides, effectors induced by a peptide of MAGE-n at residue position 159-167(QLVFGIEVV) lysed HCC cells expressing both MAGE-n and HLA-A2.1. Our results indicated that peptide QLVFGIEVV was a new HLA-A2.1-restricted CTL epitope capable of inducing MAGE-n specific CTLs in vitro. CONCLUSIONS: Identification of the MAGE-n /HLA-A2.1 peptide QLVFGIEVV may facilitate peptide-based specific immunotherapy for HCC. The combination of epitope prediction, epitope reconstruction method and immunological methods can improve the efficiency and accuracy of CTL epitope studies.

Amino Acid Sequence↗
PubMed1999

HIV-1-specific CTL responses primed in vitro by blood-derived dendritic cells and Th1-biasing cytokines.

Vaccine strategies designed to elicit strong cell-mediated immune responses to HIV Ags are likely to lead to protective immunity against HIV infection. Dendritic cells (DC) are the most potent APCs capable of priming both MHC class I- and II-restricted, Ag-specific T cell responses. Utilizing a system in which cultured DC from HIV-seronegative donors were used as APC to present HIV-1 Ags to autologous T cells in vitro, the strength and specificity of primary HIV-specific CTL responses generated to exogenous HIV-1 Nef protein as well as intracellularly expressed nef transgene product were investigated. DC expressing the nef gene were able to stimulate Nef-specific CTL, with T cells from several donors recognizing more than one epitope restricted by a single HLA molecule. Primary Nef-specific CTL responses were also generated in vitro using DC pulsed with Nef protein. T cells primed with Nef-expressing DC (via protein or transgene) were able to lyse MHC class I-matched target cells pulsed with defined Nef epitope peptides as well as newly identified peptide epitopes. The addition of Th1-biasing cytokines IL-12 or IFN-alpha, during priming with Nef-expressing DC, enhanced the Nef-specific CTL responses generated using either Ag-loading approach. These results suggest that this in vitro vaccine model may be useful in identifying immunogenic epitopes as vaccine targets and in evaluating the effects of cytokines and other adjuvants on Ag-specific T cell induction. Successful approaches may provide information important to the development of prophylactic HIV vaccines and are envisioned to be readily translated into clinical DC-based therapeutic vaccines for HIV-1.

CD4-CD8 Ratio↗
PubMed1999

CD86 (B7-2) can function to drive MHC-restricted antigen-specific CTL responses in vivo.

Activation of T cells requires both TCR-specific ligation by direct contact with peptide Ag-MHC complexes and coligation of the B7 family of ligands through CD28/CTLA-4 on the T cell surface. We recently reported that coadministration of CD86 cDNA along with DNA encoding HIV-1 Ags i.m. dramatically increased Ag-specific CTL responses. We investigated whether the bone marrow-derived professional APCs or muscle cells were responsible for the enhancement of CTL responses following CD86 coadministration. Accordingly, we analyzed CTL induction in bone marrow chimeras. These chimeras are capable of generating functional viral-specific CTLs against vaccinia virus and therefore represent a useful model system to study APC/T cell function in vivo. In vaccinated chimeras, we observed that only CD86 + Ag + MHC class I results in 1) detectable CTLs following in vitro restimulation, 2) detectable direct CTLs, 3) enhanced IFN-gamma production in an Ag-specific manner, and 4) dramatic tissue invasion of T cells. These results support that CD86 plays a central role in CTL induction in vivo, enabling non-bone marrow-derived cells to prime CTLs, a property previously associated solely with bone marrow-derived APCs.

Animals↗
PubMedDate not supplied

Kinetics of cytokine gene expression during the in vitro CTL induction against a murine nonimmunogenic tumor.

BACKGROUND: The study of the local environment around tumors, including cellular and endogenous cytokine kinetics may improve our understanding of the biological process occurring during the CTL induction. MATERIALS AND METHODS: The expression kinetics of ten cytokine genes and immune cell subsets were examined by a RT-PCR and immunohistochemistry using a nonimmunogenic murine tumor and its immunogenic variant (A7). RESULTS: In a mixed lymphocyte-parent tumor cell culture (MLTC) using in vivo A7-immunized spleen cells, where CTL induction was confirmed on day 5 of cultivation, IL-6 gene expression was promptly activated at 12 h, IL-2 and IL-4 gene expression was prominently up-regulated on days 1 and 2, and then IL-10 and TGF-beta gene expression was down-regulated from day 2 onward. In contrast, in a MLTC using non-immunized spleen cells (a CTL non-induction model), no prominent upregulation of the IL-6, IL-2 or IL-4 gene was detected, and expression of the IL-10 and TGF-beta genes increased steadily. Although numerous dendritic cells were observed in the A7 immunized spleen tissue, lower numbers of dendritic cells were evident in the non-immunized spleen tissue. CONCLUSIONS: A cellular environment that includes the presence of dendritic cells and a cytokine environment that involves the timely production of IL-6, IL-2, and IL-4, and subsequent inhibition of the immunosuppressive cytokines IL-10 and TGF-beta, appear to play an important role in induction of CTL in this model.

Animals↗
PubMed2002

Gammadelta T cells in anterior chamber-induced tolerance in CD8(+) CTL responses.

PURPOSE: Delivery of antigen to the anterior chamber (AC) of the eye induces a systemic form of tolerance, referred to as anterior chamber-associated immune deviation (ACAID). ACAID is characterized by decreases in delayed-type hypersensitivity responses and complement-fixing antibodies on subsequent challenge with an immunogenic form of the antigen. The current study was designed to test whether priming of antigen-specific CD8(+) cytotoxic T-lymphocytes (CTLs) are inhibited by injection of soluble antigen into the AC and whether gammadelta T cells play a role in the inhibition of such responses. METHODS: Antigen was administered through the AC to normal gammadelta T-cell-deficient or reconstituted gammadelta T-cell-deficient mice. Seven days after the AC injection, the mice were primed with antigen in adjuvant and 10 days later, their spleen cells were cultured for 5 to 7 days and the CTL responses measured. RESULTS: CTL responses were inhibited by antigen delivered through the AC in normal but not gammadelta T-cell-deficient mice. Tolerance was reconstituted in delta-chain knockout mice by the adoptive transfer of gammadelta T cells from normal mice. Moreover, spleen cells and splenic gammadelta(+) T cells, but not gammadelta(-) T cells, from mice injected with antigen through the AC inhibited development of CTL responses when cultured together with primed effector T cells. CONCLUSIONS: These data show, for the first time, that administration of soluble antigen in the AC inhibits development of CD8(+) cytotoxic T-cell responses and that gammadelta T cells play a critical role in inhibition of CTL responses.

Animals↗
PubMed2004

[A HLA-A2-restricted-CTL epitope variation at the N-terminal of HCV helicase and the immune response of CTLs].

AIM: To investigate a HLA-A2-restricted CTL epitope variation at the N terminal of hepatitis C virus (HCV) helicase and the proliferative response of cytotoxic T lymphocytes (CTLs) to this epitope. METHODS: Two patients infected with HCV were followed up for 7 years. Blood samples taken at the first year and the fifth year were used for viral RNA extraction. Using RT-PCR, the N terminal gene of helicase region was amplified from the extracted RNA. The amplified segments were subcloned and sequenced to assess the epitope variation. A HLA-A2-restricted CTL epitope peptide was synthesized according to the sequencing result. HLA types of the two patients were determined by serological method. The peripheral blood lymphocytes were separated from the two patients at 7th year after infection and cultured with the synthetic CTL epitope peptide to assess the CTL's proliferative response. RESULTS: In the HLA-A2(+) individual, there was an amber mutation at the first amino acid of the epitope in the first year after infection, but the amber mutation disappeared after 5 years. However, in the HLA-A2(-) individual, the epitope had neither variation nor amber mutation in 5 years after infection. 7 years after HCV infection, T lymphocytes from both individuals had no proliferative response to the epitope peptide. CONCLUSION: The amber mutation of the epitope at N terminal of helicase may be associated with viral immune escape. CTLs have no response to the epitope peptide in the N terminal of HCV helicase in the later stage of chronic HCV infection.

Adult↗
PubMed2005

[Identification of a novel HLA-A2-restrictive CTL epitope of an ovary cancer-associated antigen OVA66].

AIM: To identify a novel HLA-A2-restrictive CTL epitope of an ovary cancer-associated antigen OVA66. METHODS: Dendritic cells (DCs), induced from peripheral blood mononuclear cells(PBMCs) by cytokines, were confirmed by morphological observation and FACS. Mature DCs were pulsed with each of the two synthesized peptides which were selected as possible CTL epitopes by software analysis. The pulsed DCs were used to stimulate autologous CD8+ T cells from an HLA-A2+ healthy donor. One week later, the peptides-pulsed autologous PBMCs were used to stimulate the CD8+ T cells for another 3 times at weekly intervals. The stimulated CD8+ T cells were used as CTLs. The cytotoxicity of CTLs to target cells was detected by lactate dehydrogenase (LDH) release assay and the number of T cells secreting antigen-specific IFN-gamma in CTLs was analyzed by enzyme-linked immunospot assay (ELISPOT). RESULTS: The results of morphology observation and FACS indicated that mature DCs were induced from PBMCs. Of the two peptides, peptide L235(FLPDHINIV) induced peptide-specific CD8+ T cells that lysed HLA-A2+ T2 cells pulsed with L235 and OVA66+/HLA-A2+ SW480 cells. Compared with control peptide, L235 increased the number of IFN-gamma producing T cells. CONCLUSION: This novel OVA66-derived CTL epitope L235 can induce HLA-A2-restrictive CTL response, which lays the foundation for preparation of tumor-specific peptide vaccine.

Amino Acid Sequence↗
PubMed2006

[CTL response to pre-erythrocytic stage vaccine candidate of plasmodium falciparum in HLA-A*0201 transgenic mice detected by ELISPOT assay].

The importance of cytotoxic T-lymphocyte (CTL) against malaria parasite in pre-erythrocytic stage has been presented in relevant researches. In order to investigate whether one CTL epitope (YLNKIQNSL) involved in a chimeric pre-erythrocytic stage vaccine candidate of Plasmodium falciparum which was expressed and purified in the laboratory can stimulate in vivo CTL response, HLA-A*0201 transgenic mice were immunized with this vaccine candidate. Enzyme-linked immunosorbent spot (ELISPOT) assay was performed on the splenocytes from the immunized transgenic mice. Positive result indicated that this CTL epitope can be in vivo processed and correctly presented.

Animals↗
PubMed2006

[Production of specific CTL induced by exosomes derived from K562 cells].

The aim of this study was to investigate whether exosomes derived from K562 cells and human monocyte-derived dendritic cells (DCs) transfected with total RNA of K562 cells are capable of inducing antigen-specific cytotoxic T lymphocytes (CTL) responses in vitro. DCs were generated from peripheral blood mononuclear cells (PBMNC) of healthy volunteers in the presence of GM-CSF and IL-4, and then were transfected with K562 RNA by using DOTAP lipofection. Exosomes was extracted from the supernatant of DCs and K562 cells. The T cell were activated to be tumor specific CTL after DCs and exosomes were co-cultured with autologous T cells derived from healthy volunteers' PBMNC. The effect of CTL on K562 cells was detected by MTT assay. The results showed that treatment of T cells with exosomes derived from K562 cells or DCs transfected with total RNA of K562 cells could significantly promote their killing ability on K562 cells as compared with untreated T cells (P < 0.05). The killing ability of T cells treated with exosomes on K562 cells was stronger than on HL-60 cells (P < 0.05). It is concluded that the specific CTL immune response to leukemia cells can be induced by exosomes derived from K562 cells.

Dendritic Cells↗
PubMed1990

Anti-proliferative effect of IFN-gamma in immune regulation. IV. Murine CTL clones produce IL-3 and GM-CSF, the activity of which is masked by the inhibitory action of secreted IFN-gamma.

We have demonstrated recently that rIFN-gamma inhibits the proliferation of murine bone marrow cells stimulated with rIL-3 or recombinant granulocyte-macrophage (GM)-CSF. In light of this finding, three murine CD8+ CTL clones whose supernatants had been shown previously not to contain detectable levels of CSF activity but which contained a relatively high level of IFN-gamma were reassessed for their ability to secrete IL-3 and GM-CSF. Supernatants from CTL clones activated with anti-CD3 mAb failed to stimulate the IL-3-dependent cell line FDCP1. However, these supernatants were indeed able to stimulate the proliferation of FDCP1 cells if anti-IFN-gamma mAb was present. This stimulatory activity was specifically neutralized by anti-IL-3 mAb. Supernatants from two of the three clones stimulated the proliferation of a GM-CSF-responsive HT-2 cell line, and this activity was neutralized by anti-GM-CSF antibody. The otherwise modest ability of CTL supernatants to stimulate the proliferation of fresh bone marrow cells was augmented considerably in the presence of anti-IFN-gamma mAb, and this activity was appropriately blocked by anti-IL-3 and anti-GM-CSF antibodies. mRNA for IL-3 and GM-CSF, as well as for IFN-gamma and TNF-alpha, was detected in cells that secreted those lymphokines, and the time course of appearance of each mRNA correlated with secretion of the appropriate lymphokine activity. However, the time course of mRNA accumulation for each lymphokine was distinct, the order of expression of these genes apparently being TNF-alpha, then IFN-gamma and GM-CSF, and finally IL-3. Our results emphasize that potential interactions among lymphokines must be considered when interpreting data obtained from lymphokine bioassays and suggest an immunoregulatory role for CTL through the secretion of several of the same lymphokines produced by HTL.

Animals↗
PubMed1985

Presentation of Class I antigens on T cells can induce the generation of antigen-specific CTL.

Cytotoxic T lymphocyte (CTL) lines generally require a source of specific antigen to continue to proliferate in vitro. We previously showed that populations of mononuclear cells grown in medium containing interleukin 2 (IL 2) and composed largely of activated T cells were able to present Class I alloantigen to CTL lines. On the basis of these findings we were interested to know whether T cells themselves were able to present antigen or whether this was a function of the small number of contaminating non-T cells. To answer this question, populations of activated or resting mononuclear cells were rigorously depleted of non-T cells before use as antigen-presenting cells. We observed that populations composed of greater than 99% T cells were able to support the differentiation of antigen-specific CTL. These results were confirmed by using cells from an established T cell line. The proliferation of the same lines, however, was less than that of lines grown in the presence of antigen-presenting cells containing some non-T cells. These results suggest that although T cells can present Class I alloantigens to CTL, they may be less effective in triggering cell division than populations containing a source of non-T cells.

Antigen-Presenting Cells↗
PubMed1987

Recognition of the beta-2 microglobulin-B molecule by a CTL clone.

In this report we offer evidence that the beta-2 microglobulin-B (beta 2M-B) molecule is recognized by a cytotoxic T lymphocyte (CTL). Production of GA5, a CTL clone reactive against a membrane antigen with the same strain distribution pattern as beta 2M-B, is described. This clone lysed syngeneic target cells in which native beta 2M-A molecules had been exchanged with beta 2M-B molecules by incubating the cells in serum from beta 2M-B-positive mouse strains. Conversely, the CTL clone GA5 failed to lyse its specific target when beta 2M-B molecules had been exchanged with beta 2M-A molecules by incubating the cells in serum from beta 2M-A-positive, beta 2M-B-negative mouse strains. Strain combinations were chosen so as to limit reactivity to beta 2M and to preclude reactivity to H-3 antigens, thus indicating CTL clone GA5 to be reacting specifically with beta 2M-B.

Animals↗
PubMed1976

Generation of cytotoxic T lymphocytes in vitro. VII. Suppressive effect of irradiated MLC cells on CTL response.

Irradiated cells obtained from MLC at the peak of the CTL response caused profound suppression of generation of CTL when added in small numbers at the initiation of primary MLC prepared with normal spleen cells. The inhibitory activity of the MLC cells was not affected by irradiation (1000 rads) but was abolished by treatment with anti-theta serum and complement. The suppression was immunologically specific. The response of A (H-2a) spleen cells toward C3H (H-2k) alloantigens was suppressed by irradiated MLC cells obtained from MLC prepared with A spleen cells and irradiated C3H-stimulating cells, whereas the response of A spleen cells toward DBA/2 (H-2d) alloantigens was affected relatively little. However, if irradiated C3H X DBA/2 F1 hybrid spleen cells were used to stimulate A spleen cells in MLC, addition of irradiated MLC cells having cytotoxic activity toward C3H antigens abolished the response to both C3H and DBA/2 antigens. The response to DBA/2 antigens was much less affected when a mixture of irradiated C3H and DBA/2 spleen cells was used as stimulating cells. Thus, the presence of MLC cells having cytotoxic activity toward one alloantigen abolished the response to another non-cross reacting antigen only when both antigens were present on the same F1 hybrid-stimulating cells. This suppression of generation of CTL by irradiated MLC cells apparently involves inactivation of alloantigen-bearing stimulating cells as a result of residual cytotoxic activity of the irradiated MLC cells. This mechanism may be active during the decline in CTL activity noted in the normal immune response in vivo and in vitro.

Animals↗
PubMed1983

Isolation of alloreactive CTL clones with cyclical changes in lytic activity.

We have isolated two H-2Dd specific CTL clones from CBA anti-DBA/2 MLC that undergo changes in lytic activity against tumor and Con A blast target cells as a consequence of weekly stimulation with irradiated allogeneic cells and conditioned medium from secondary MLC. Lytic activity is highest on days 2 to 3 after stimulation, and lowest on days 5 to 7. CTL that had been irradiated on day 0 before stimulation have significantly greater activity on day 2. Conditioned media alone, in the absence of added allogeneic stimulator cells is capable of supporting, in a dose-dependent fashion, the increase in activity. Collectively, these changes are similar to those described for the induction of lytic activity in nonlytic CTL populations from long-term MLC, and suggest that these cloned lines may be useful to study the modulation of lytic activity of CTL in culture.

Animals↗
PubMed1984

Mouse alloantibodies capable of blocking cytotoxic T cell function. V. The majority of I region-specific CTL are Lyt-2+ but are relatively resistant to anti-Lyt-2 blocking.

In an attempt to solve the conflict concerning the correlation between the Lyt-2 phenotype of T cells subsets and the type of the MHC antigens involved in the recognition by T cells, class 2 (I region) antigen-specific CTL were studied for their Lyt phenotypes and the sensitivity to the blocking effects of anti-Lyt-2,3 antibodies. To avoid contamination by CTL to class 1 antigens such as Qa antigens, A.TH anti-A. TL attackers and A.TH anti-A attackers were tested on LPS blasts of the A strain and the A.TL stain, respectively. By using these combinations, it was shown that the majority of I region-specific killers were Thy-1+, Lyt-1+23+. Specific target cell lysis by these cells were, however, found to be far less sensitive to the blocking effects of various monoclonal antibodies to the Lyt-2,3 antigens than conventional class 1-specific CTL. This conclusion was drawn by directly comparing the sensitivity of the I region-specific and K region-specific killing by identical numbers of the same attacker cells (A.TH anti-A). No significant difference was seen between the primary and the hyperimmune CTL. Lyt-2-, Thy-1+ killer cells with I region specificity could be induced when Lyt-2-depleted A.TH responder cells were stimulated in vitro. Such Lyt-2- killer cells were not induced to the H-2K alloantigen.

Animals↗
PubMed1983

In vivo development of cytolytic T lymphocytes (CTL) to hapten-altered self: MIs-disparate cells facilitate the response by neutralizing IL 2 inhibitor.

Inability to develop CTL in vivo to hapten-altered self can be attributed in part to an inhibitor of interleukin 2 (IL 2) that is present in the serum of normal mice. We have shown earlier that hapten-specific CTL can be generated in C3H mice (H-2k, MIsc) provided CBA/J (H-2k MIsd) spleen cells are injected simultaneously with hapten-modified syngeneic spleen cells into the hind foot paws. In efforts to determine whether serum levels of the inhibitor of IL 2 are altered as a consequence of this successful immunization method, we have compared the activity of the inhibitor in serum at intervals after the injection of syngeneic spleen cells, CBA spleen cells, or TNP-C3H spleen cells alone or together with CBA spleen cells, by using a murine IL 2-dependent, cloned cytotoxic T cell line, CT-6. The results indicate that inhibitor was neutralized optimally 48 to 72 hr after injection of TNP-C3H spleen cells mixed with CBA/J spleen cells. The order in which neutralization occurred was as follows: TNP-C3H cells + CBA/J cells greater than CBA cells greater than TNP-C3H cells greater than normal C3H spleen cells. Furthermore, supernatants from cultures of C3H lymph node cells stimulated in vivo with CBA/J cells also contained IL 2 activity. Thus, injection of CBA/J cells with TNP-modified syngeneic spleen cells produces IL 2 in vivo in sufficient quantity to neutralize the activity of the inhibitor as well as to facilitate the maturation of pre-CTL into hapten-altered self-specific CTL.

Animals↗
PubMed1984

Memory CTL-hybridoma: a model system to analyze the anamnestic response of cytolytic T lymphocytes.

We have previously described monoclonal CTL-hybridomas growing continuously in culture in the absence of a known antigenic stimulus or growth-promoting factor(s), exhibiting specific anti-H-2Db killing activity in vitro after a distinct 2-hr lag period before the onset of lysis. Here we provide evidence indicating that the hybridoma Md 26.15 represents "memory" CTL, and we examine the mechanism whereby they respond to antigen/mitogen. The brief period (2 to 3 hr) required for stimulation suggests that expression of potentiated effector function(s) after stimulation requires no cell replication. The frequency of effector hybridoma cells capable of specific binding to target cells before and after stimulation is the same, as determined in a direct hybridoma-target cell conjugation test, although cytolytic activity is markedly enhanced. On the other hand, kinetic and cell dispersion assays indicate that the potentiation of cytolytic activity can be attributed to shortening of the lag period of killing as well as to a small enhancement in the recycling ability of cytolytic effectors. We suggest that shortening of the lag period involves activation of potential effectors, which is manifested at a post-binding stage of effector-target interaction. The CTL hybridoma described herein provides a unique model system for studying CTL reactivation.

Animals↗
PubMed1983

The functional significance, distribution, and structure of LFA-1, LFA-2, and LFA-3: cell surface antigens associated with CTL-target interactions.

Three cell surface antigens associated with the cytolytic T lymphocyte(CTL)-target cell interaction were identified by generation of monoclonal antibodies (MAb) against OKT4+, HLA-DR-specific CTL and selection for inhibition of cytolysis in a 51Cr-release assay. These MAb block cytolysis by both OKT4+ and OKT8+ CTL and the proliferative responses to PHA and the mixed lymphocyte response (MLR). LFA-1 is an antigen widely distributed on lymphoid tissues and is composed of two polypeptides of 177,000 and 95,000 Mr on all cell types studied. Anti-LFA-1 MAb block NK cell-mediated cytolysis in addition to T lymphocyte-mediated cytotoxicity and proliferation. LFA-2 (Mr = 55,000 to 47,000), a determinant on the sheep red blood cell receptor, is expressed by T cells but not B cells and appears specific for T cell functions. LFA-3 (Mr = 60,000) is a widely distributed antigen present on both hematopoietic and nonhematopoietic tissues and appears to only be involved in T cell functions. MAb to LFA-1 and LFA-2 inhibit function by binding to effector cell surface molecules, whereas anti-LFA-3 MAb appear to block by binding to the target cells. Together with previously described molecules, LFA-1, LFA-2, and LFA-3 demonstrate the complexity of CTL-mediated cytotoxicity at the molecular level.

Antibodies, Monoclonal↗