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At least 775 records · Page 43Linked to original sources
PubMed1980

A "nonidiotypic" inhibition of influenza-immune H-2-restricted CTL by an anti-T cell serum.

A xenogeneic serum directed at alloimmune CTL is shown to block H-2-restricted anti-viral CTL activity. Extensive absorption studies with targets and effector cells indicate that the blocking is at the level of the CTL and not the target cells. Inhibition is demonstrated for influenza-specific cytotoxicity operating in the context of 3 distinct H-2 haplotypes, suggesting that the serum is not directed at antigen-recognition structures. Kinetic studies on the addition of RAT to an ongoing 51Cr release assay further support the hypothesis that inhibition is not operating via the idiotypic region of the antigen receptor. We suggest that RAT is specific for CTL surface structures involved in nonrecognition events--possibly the lytic sites or a conserved region (idiotype-negative) of th antigen-binding receptor.

Animals↗
PubMed1980

Mechanisms of immune lysis. II. CTL-induced nuclear disintegration of the target begins within minutes of cell contact.

Within minutes of CTL-target interaction, the intracellular disintegration of the target cell nucleus begins. This nuclear event satisfies the ionic and temperature requirements that have been described by others as important in CTL-mediated lysis. Such nuclear disintegration does not occur in Ab+C-lysed targets. Thus the target cell nucleus appears to signal a primary event in CTL-mediated lysis that distinguishes the CTL lytic mechanism from that of Ab+C.

Animals↗
PubMed1994

Direct sequence identification and kinetic analysis of an MHC class I-restricted Listeria monocytogenes CTL epitope.

Murine infection with the intracellular bacterium Listeria monocytogenes elicits MHC class I-restricted CTL with specificity for multiple bacterial peptides. The variety and relative abundance of self-peptides bound by MHC molecules make identification of pathogen-derived peptides difficult. In this report, the sequence of a pathogen-derived CTL epitope is determined by direct analysis of peptides extracted from MHC class I molecules. The epitope, p60 217-225, is presented to L. monocytogenes-specific CTL by the H-2Kd MHC class I molecule and is derived from p60, a secreted invasion-associated protein. Quantitation of p60 217-225 in infected cells shows that this epitope is detectable within 2 h of infection and, after a 9-h infection, there are over 3000 epitopes per infected cell. This contrasts with listeriolysin 91-99, the other major L. monocytogenes epitope, which is present in quantities below 200 epitopes per cell until 5 h of infection and reaches 800 epitopes per cell 9 h after infection. This report shows that identifying new T lymphocyte epitopes by direct sequence analysis of peptides isolated from MHC molecules is feasible. Furthermore, kinetic and quantitative analysis of T cell epitopes in infected cells is a useful approach to investigate the multispecific CTL response to complex intracellular pathogens.

Amino Acid Sequence↗
PubMed1993

Hepatitis C virus-specific CTL responses in the liver of chimpanzees with acute and chronic hepatitis C.

Hepatitis C virus (HCV)-specific CTL responses were evaluated in two chimpanzees (Pan troglodytes) during the acute and chronic phases of HCV infection. CD8+ T lymphocytes were isolated from liver tissue homogenates using anti-CD8 antibody-coated magnetic beads and then stimulated with anti-CD3 antibodies, IL-2, and irradiated human PBMC using limiting dilution culture conditions. HCV-specific cytotoxic activity of expanding CD8+ cell lines was assessed against autologous lymphoblastoid cell lines infected with recombinant vaccinia virus vectors encoding HCV Ag. CD8+ T cell lines specific for structural and nonstructural proteins of HCV were established from both animals. Cytolytic activity was blocked with anti-CD8 or anti-class I MHC antibodies, indicating that class I MHC molecules were involved in presentation of viral Ag to the CTL. Overlapping synthetic peptides were used to define a 12 amino acid segment of the nonstructural 3 (NS3) protein recognized by CTL lines from both chimpanzees. Studies with truncated peptides revealed that these CD8+ cell lines were directed against overlapping epitopes presented by distinct class I restriction elements of the chimpanzee MHC complex. CD8+ cell lines with identical specificities for an NS3 epitope were generated from one chronically infected animal at 16 and 28 wk postinfection. These results indicate that virus-specific CTL populations persist in the liver for months, but are unable to resolve chronic HCV infection.

Acute Disease↗
PubMed1995

CTL specific for the tyrosinase autoantigen can be induced from healthy donor blood to lyse melanoma cells.

CTL that lyse melanoma cells were previously isolated from several melanoma patients. Such CTL recognize autologous proteins, indicating the occurrence of autoreactive T cells in melanoma patients. We have now raised CTL, using responding T lymphocytes from healthy donor blood, that lysed not only cells incubated with an HLA-A*0201-binding tyrosinase peptide but also melanoma cells endogenously processing and presenting the epitope. Our results suggest that autoreactive CTL precursors are present in healthy donor blood and can be activated in vitro with synthetic peptides presented on appropriate APCs. Therefore, tissue-specific, autoantigen-derived peptides might be useful in immunotherapy of both poorly and nonimmunogenic tumors.

Amino Acid Sequence↗
PubMed1995

Simian immunodeficiency virus (SIV)-specific CTL in cerebrospinal fluid and brains of SIV-infected rhesus macaques.

Simian immunodeficiency virus (SIV)-specific CD8+ CTL were isolated from blood, cerebrospinal fluid, and brains of rhesus macaques infected i.v. with SIV. CTL were found as early as 1 wk postinfection and their appearance correlated with a decrease of viral Ag (p27) found in the blood. CTL isolated from cerebrospinal fluid and/or brain often recognized different viral proteins than CTL isolated from blood, suggesting either a unique migratory pattern to the central nervous system or a difference in activation/retention of lymphocytes in these compartments.

Amino Acid Sequence↗
PubMed1994

Studies of the mechanism of cytolysis by HIV-1-specific CD4+ human CTL clones induced by candidate AIDS vaccines.

Vaccine-induced, virus-specific CTLs may rapidly eliminate the host cells that first become infected after virus exposure, thereby preventing disseminated infection. Thus, there is much interest in the ability of candidate AIDS vaccines to elicit CTLs. All HIV-1 envelope (env) protein-based vaccines tested to date in seronegative humans induce CTLs from the CD4+ subset. Because the mechanism of cytolysis by CD4+ CTLs is controversial, a detailed study of the cytolytic reactions mediated by vaccine-induced, HIV-1-specific human CD4+ CTL clones was conducted. CD4+ CTL clones induced rapid destruction of Ag-pulsed target cells. Lysis was readily detectable within 15 min. Lysis was not a result of syncytium formation between CD4+ effector cells and env-expressing targets. Target cell destruction was not dependent upon de novo RNA or protein synthesis in either the effector or the target cell. Expression of perforin mRNA was detected by Northern blotting and reverse-transcriptase-PCR in CD4+ CTL clones but not in autologous B lymphoblastoid cell lines. Immunohistochemical studies demonstrated perforin protein in cytoplasmic granules in CD4+ CTL clones. Lysis by CD4+ CTLs was strictly dependent upon extracellular Ca2+ and was highly specific, with no lysis of innocent bystander cells. DNA fragmentation was detectable in target cells, but did not precede 51Cr release. Taken together, these results provide a dramatically different view of cytolysis by human CD4+ CTLs. Target cells are lysed by a rapid and efficient mechanism that involves a preformed mediator and that is functionally similar to the mechanism used by CD8+ CTLs.

AIDS Vaccines↗
PubMed1994

Heightened intragraft CTL gene expression in acutely rejecting renal allografts.

The role of CTL in the immunopathogenesis of acute cellular rejection is controversial. To further define the relationship of activated CTLs to rejection, we analyzed gene expression of three CTL-derived effector molecules in renal allograft biopsies. CTLs are endowed with the ability to promote allograft damage through the elaboration of these highly cytopathic molecules. Intragraft gene transcript levels were determined for granzyme B, perforin, and TIA-1 and correlated with the immunologic status of the allograft as categorized by conventional clinical and histologic criteria. The categories were acute cellular rejection, chronic rejection, elements of both acute and chronic rejection, and no evidence of rejection. Biopsies were snap-frozen, total RNA extracted, and the mRNA converted to cDNA by reverse transcription. Levels were quantitated by competitive template PCR techniques. Intragraft granzyme B and perforin transcripts were highly restricted to biopsies in the acute cellular rejection category. TIA-1 expression was more ubiquitous but significantly higher transcript levels were found in the acute rejection category. The presence of these transcripts in acute cellular rejection samples implicates CTL in the pathogenesis. Moreover, intragraft CTL-specific transcript levels may serve as markers of rejection.

Base Sequence↗
PubMed1993

[Analysis on the CTL-p frequency before and after immunotherapy for patients with unexplained habitual abortion].

The efficacy of immunotherapy with paternal lymphocytes has been reported as a treatment for unexplained habitual aborters. The underlying mechanisms, however, have not yet been fully elucidated. We have previously reported the appearance of humoral blocking factors which inhibited the response of maternal lymphocytes to paternal cells. Although studies concerning changes in cellular immunity in vaccinated patients have been reported, further analyses are required to elucidate the underlying mechanisms. In this context, we have investigated the changes in cytotoxic T lymphocyte precursor (CTL-p) frequency in 10 patients who were unexplained recurrent aborters before and after vaccination with the husband's lymphocytes using a sensitive limiting dilution culture system. The results obtained were as follows; 1. The reciprocal number for the frequency of CTL-p in patients reacting to their husband's lymphocytes before immunotherapy was 93,620.0 +/- 61,893.3 and that after the immunotherapy was 33,860.0 +/- 33,578.8. The frequency, thus, significantly increased after the immunotherapy (p < 0.01). 2. The frequency of CTL-p reacting to an unrelated third party's lymphocytes showed no significant change before and after the immunotherapy even though the HLA antigens in the husband and the third party were the same. 3. The sera, which were collected after the immunotherapy, were observed to undergo a decrease in the frequency of CTL-p.

Abortion, Habitual↗
PubMed1996

Induction of microvariant-specific CTL lines reactive to a single amino acid mismatch in bulk cultures using a transfectant expressing a single HLA class I molecule.

Alloreactivity against micromismatches in MHC class I molecules is difficult to measure. Here, we describe an in vitro model with which it is possible to examine alloreactivity against a single HLA class I allotype. The HLA class I- and class II-negative myelocytic leukemia cell line K562 was transfected with a genomic DNA clone carrying B*4403 to express a single allotype. CTL lines were generated from normal individuals carrying B*4402, B*4403, or unrelated HLA-B alleles by stimulation with B*4403- transfected K562. The bulk CTL lines generated from B*4402+ T cells against B*4403 that carry a single amino acid disparity at position 156 were specific for B*4403+ targets and did not react with targets carrying any other HLA allotype. However, the CTL lines generated from B44-negative individuals exhibited killing of the targets bearing not only B44, but also B44 CREG and a few other B alleles. Reverse transcriptase-PCR analysis of TCRs, expressed in the CTL clones uniquely specific for B*4403, showed that TCR V beta usage of alloreactive T cells directed against B*4403 was diverse but nonrandom and was affected by the HLA background of the responder. Thus, the K562-HLA transfectant system provides a useful in vitro tool to analyze alloreactivity against a single class I allele and to aid in the prediction of alloreactivity in unrelated marrow transplantation.

Alleles↗
PubMed1996

Specificity and degeneracy of minor histocompatibility antigen-specific MHC-restricted CTL.

Random peptide libraries were employed to investigate the specificity of Ag recognition by H-3-specific, H-2K(b)-restricted CTL clones. The peptide libraries consist of octapeptides with one defined sequence position and mixtures of 19 amino acids (all proteinogenic amino acids except for cysteine) in the remaining seven sequence positions. The complete set of 152 peptide libraries includes all octapeptides possible with these amino acids. Responses of the CTL clones to these peptide libraries reveal patterns of preferred epitope amino acids. Depending on the CTL clone tested, varying numbers of different amino acids were identified for the different sequence positions indicating degeneracy of Ag recognition. Sequences for synthetic epitopes active at low pM concentrations could be deduced from these patterns. They confirm that TCRs of CTL clones do not exhibit specificity for unique ligand structures but rather can interact with sets of ligands. The sequences of peptides recognized by a single clone exhibit great sequence heterogeneity.

Amino Acid Sequence↗
PubMed1996

The weak CD8+ CTL response to an influenza hemagglutinin epitope reflects limited T cell availability.

One of the two class I MHC (H-2Kd)-restricted immunogenic regions identified on the influenza virus strain A/Japan/57 (H2N2) hemagglutinin (HA) encompasses two distinct, partially overlapping epitopes. These epitopes map to residues 204 to 212 (JHA 204-212) and 210 to 219 (JHA 210-219), respectively. When we investigated the magnitude of the CTL responses of H-2d BALB/c mice to these two epitopes, we found that the JHA 204-212 nonamer epitope is immunodominant, eliciting vigorous CTL responses in BALB/c mice immunized with A/Japan/57 virus. In contrast, the CTL response to the JHA 210-219 decamer epitope was weak and variable. The subdominance of the JHA 210-219 was not due to low affinity binding of JHA 210-219 to H-2Kd or to inefficient processing of this epitope in vivo. Rather, an analysis of CTL precursor (pCTL) frequency by limiting dilution showed that the frequency of pCTL to the JHA 210-219 epitope was at least 10-fold lower than the frequency of pCTL to the JHA 204-212 epitope, implying that the low and variable response to the JHA 210-219 epitope was due to a limited number of CD8+ T cell precursors directed to JHA 210-219. This hypothesis was further supported by the finding of limited heterogeneity in reactivity pattern displayed by short term bulk cultures of the JHA 210-219-specific CTLs for cross-reactive epitopes. Implications of these findings for vaccine design and for T lymphocyte function and repertoire development are discussed.

Amino Acid Sequence↗
PubMed1996

CTL recognition of an altered peptide associated with asparagine bond rearrangement. Implications for immunity and vaccine design.

The extent to which peptides containing chemically and post-translationally modified amino acid side chains are recognized by primed CTL has not been clearly defined. We report on the CTL recognition of a MHC class I-restricted peptide containing a cyclized asparagine (succinimide) residue. This modification of the asparagine side chain is a common intermediate structure during deamidation, isomerization, and bond rearrangements of amide-containing amino acids and also occurs as a side reaction in peptide synthesis. The CTL specifically recognized the succinimide-containing peptide showing only weak cross-reactivity at high concentrations of the parent peptide containing unmodified asparagine. Similarly, CTL raised against the parent peptide did not recognize the succinimide derivative of this peptide. Naturally processed forms of these structures are likely to occur given the importance and frequency of deamidation both in vitro and in vivo. Moreover, since succinimide intermediates of deamidated peptides can occasionally be very stable, these peptides have the potential to act as altered self-Ags with significant implications for autoimmunity. In addition, unwanted and potentially hazardous specificities may be elicited when using synthetic peptides in subunit vaccines in which succinimide residues may form spontaneously during storage or chemical synthesis.

Amino Acid Sequence↗
PubMed1996

Morphine suppresses the alloantigen-driven CTL response in a dose-dependent and naltrexone reversible manner.

Previous studies have shown morphine (50.0 mg/kg, s.c.) suppresses cytotoxic T lymphocyte (CTL) activity in alloimmunized mice. The present study was undertaken to assess the dose-dependent nature of the suppressive effect of subchronic morphine exposure on CTL activity in vivo. In alloimmunized ICR mice, morphine (10.0-100.0 mg/kg, s.c.) administered daily for 5 days significantly suppressed CTL activity ( > 50%) in a dose-dependent and naltrexone (10.0 mg/kg, s.c.)-reversible fashion. The morphine-treated mice showed tolerance to the drug after daily exposure over 5 days as determined by measuring tail flick latency during thermal application. CD4(+)- and CD8(+)-depletion studies showed that effector cells were predominately CD8+ and mediated cytolysis through a Ca(++)-dependent pathway. Splenocytes obtained from the morphine (56.0-100.0 mg/kg)-treated, alloimmunized mice produced significantly less (30-40%) interferon-gamma but not interleukin-2 or interleukin-10 after antigen stimulation but not concanavalin A stimulation. Furthermore, this effect was dose- and time-dependent. In addition, there was a modest decrease (10%) in the interferon-gamma transcript level from the morphine (56.0-100.0 mg/kg)-treated, alloimmunized mice compared with vehicle-treated, alloimmunized mice as determined by quantitative reverse transcription-polymerase chain reaction. However, there were no differences in the perforin transcript levels between morphine- and vehicle-treated mice. Collectively, these results suggest that subchronic morphine exposure suppresses CTL activity in tolerized, alloimmunized mice through a pathway that may peripherally involve interferon-gamma production.

Animals↗
PubMed1996

Exhaustion of CTL memory and recrudescence of viremia in lymphocytic choriomeningitis virus-infected MHC class II-deficient mice and B cell-deficient mice.

To study the contribution of CD4+ T cells and B cells to antiviral immunity and long term virus control, MHC class II-deficient and B cell-deficient mice were infected with lymphocytic choriomeningitis virus. In class II-deficient mice, which lack CD4+ T cells, the primary CTL response is virtually intact, and the infection is initially controlled in most organ sites including the blood. However, approximately 2 mo postinfection, CTL memory cannot be detected, and recrudescence of viremia to titers as high as seen during the acute phase of the infection is observed. To investigate whether this phenomenon could reflect participation of B cells and/or Abs in long term virus control, similar experiments were performed with mice that do not have mature B cells because of a disrupted membrane exon of the mu chain gene. In these mice, the cell-mediated immune response was slightly delayed, but transient virus control was observed in most mice. However, approximately 3 mo postinfection, blood virus titers were as high as observed during the acute infection, and no CTL memory could be demonstrated. These results indicate that Abs and/or B cells are required for permanent virus control and that in their absence, the virus-specific CTL potential becomes exhausted. Together our results indicate that while CD8+ cells play a dominant role in acute virus control, all three major components of the immune system are required for long term virus control.

Acute Disease↗
PubMed1995

Usefulness of frequency analysis of cytotoxic T-lymphocytes precursors (CTL-p) for selection of HLA matched unrelated marrow donors.

A child with Sanfilippo syndrome and 5 potential unrelated marrow donors were typed serologically, tested in mixed lymphocyte reaction and typed by restriction fragment length polymorphism analysis in attempt to find a suitable donor. All donors were found to be identical with the recipient, however, these studies were not conclusive in identifying the best match donor. Therefore, recipient-donor pairs were examined by HLA-DR oligotyping. In addition we have studied the potential of cytotoxic T-lymphocytes precursors (CTL-p) analysis as a means of selection for matched unrelated donors. Low frequencies (1/10(5)) of pretransplant CTL-p correlated with oligotyping identity in all donor-recipient pairs evaluated. In one case oligotyping disclosed a previously unrecognized HLA-DRB1 disparity. This resulted in high frequencies of CTL-p (1/35,000). Based on this experience we can argue that CTL-p analysis may be used as an additional tool for selection of compatible unrelated marrow donors.

Bone Marrow Transplantation↗
PubMed1996

Lack of requirement for SHP-1 in both Fas-mediated and perforin-mediated cell death induced by CTL.

The Fas (CD95)-transmitted cell death signal has been reported to involve a protein tyrosine phosphatase, SHP-1. We analyzed the role of SHP-1 in the Fas-dependent as well as the perforin-dependent pathways of CTL-mediated killing using target cells prepared from SHP-1-deficient motheaten mice. Con A blast targets prepared from both a motheaten mouse and a phenotype-normal littermate were equally sensitive to the cytolysis and DNA fragmentation induced by both perforin-deficient Fas-dependent CTL and Fas ligand-deficient perforin-positive CTL. Fas-induced DNA degradation detected by the terminal deoxynucleotide transferase reaction was also observed in the killing of motheaten thymocytes by a Fas-based CTL as well as by anti-Fas mAb. These data cast doubt on the involvement of SHP-1 in Fas-induced lymphoid cell death.

Animals↗
PubMed1997

Human T cell leukemia virus type I (HTLV-I)-specific CD8+ CTL clones from patients with HTLV-I-associated neurologic disease secrete proinflammatory cytokines, chemokines, and matrix metalloproteinase.

Human T cell leukemia virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a chronic, progressive neurologic disease characterized by marked degeneration of the spinal cord and the presence of infiltrating CD8+ T cells and macrophages. HAM/TSP patients have very high frequencies of HTLV-I-specific CD8+ CTL in peripheral blood and in cerebrospinal fluid. In this study, we show that HAM/TSP patients also have elevated levels of peripheral blood CD8+ T cells that produce intracellular IFN-gamma. To address the potential role of soluble mediators secreted by CD8+ T cells in the pathogenesis of HAM/TSP, we have analyzed the capacity of a panel of nine HTLV-I-specific CD8+ CTL clones derived from three HAM/TSP patients to secrete cytokines, chemokines, and matrix metalloproteinases. The results demonstrate that the majority of these CTL clones secrete IFN-gamma, TNF-alpha, macrophage-inflammatory protein-1alpha and -1beta, IL-16, and matrix metalloproteinase-9. These findings indicate that HTLV-I-specific CD8+ CTL are an important source of proinflammatory soluble mediators that may contribute significantly to the pathogenesis of HAM/TSP.

Chemokines↗