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M Dohlsten

Publications and source records attributed to M Dohlsten.

At least 73 records · Page 4Linked to original sources
PubMed1996

TCR alpha beta+ anti-tumor cytolytic T lymphocytes express NKR-P1 whilethe anti-tumor activity of TCR gamma delta+ T lymphocytes is not correlated to NKR-P1 expression.

The CD8 alpha alpha homodimer as well as the NK cell receptor-protein 1 (NKR-P1) have been implicated to be preferentially expressed by T cells that develop extrathymically. We have earlier shown that intraperitoneal administration of radiated syngeneic W439 lymphoma cells in rat induces tumor-specific cytotoxic T cells (CTL) expressing the TCR alpha beta receptor as well as the TCR gamma delta receptor. In the present study we have addressed the expression of CD8 alpha alpha /alpha beta and NKR-P1 on these CTL and their correlation to cytotoxicity activity against the W439 tumor. The induced CD8+ T cells differentiated to effective cytotoxic cells regardless of the CD8 composition. NKR-P1+ T cells expressing CD8 were found in the peritoneal cavity of untreated rats and this cell population was markedly increased upon lymphoma immunization. Both TCR alpha beta+ cells and TCR gamma delta+ cells expressing NKR-P1 showed high cytotoxicity against the tumor. TCR gamma delta+ NKR-P1- cells were also cytotoxic against the tumor, while TCR alpha beta+ NKR-P1- cells showed no cytotoxicity. NKR-P1+ T cells (TCR alpha beta+ and TCR gamma delta+) were not cytotoxic against NK sensitive targets, which contradicts earlier data implicating a correlation between the expression of NKR-P1 and MHC-unrestricted cytotoxicity. In conclusion, TCR alpha beta+ anti-lymphoma CTL express high levels of LFA-1 and NKR-P1, while the TCR gamma delta+ CTL are not dependant on NKR-P1. These results suggest that NKR-P1 has a different function within the TCR alpha beta+ CTL than within the TCR gamma delta+ CTL in the recognition process of these lymphoma cells.

Animals↗
PubMed1996

Mutations in the MHC class II binding domains of staphylococcal enterotoxin A differentially affect T cell receptor Vbeta specificity.

C-terminal residues of staphylococcal enterotoxin A (SEA), including H187, D225, and D227, are involved in moderate affinity binding to MHC class II beta-chain, whereas N-terminal residues, including F47, are involved in low affinity binding to MHC class II alpha-chain. The effect of alanine substitutions at residues D227 or F47 on induction of T cell proliferation and the expansion of specific TCR Vbeta families was determined. SEA wild type specifically activated T cells expressing Vbeta1, Vbeta5.2, Vbeta6, Vbeta7, Vbeta9, Vbeta18, and Vbeta22. Although SEA-D227A exhibited substantially reduced mitogenicity compared with SEA wild type, it expanded the same Vbeta-bearing T cells, except those expressing Vbeta1. By contrast, SEA-F47A, which was slightly less mitogenic than SEA wild type, induced expansion only of T cells expressing Vbeta6, Vbeta7, and to a lesser extent Vbeta22. Therefore, specific mutations affecting either MHC class II alpha or beta binding sites differentially affect the Vbeta specificity of this superantigen. The lack of expansion in four of seven Vbeta families by SEA-F47A suggests that the class II alpha binding site may position SEA on the MHC class II molecules in an appropriate conformation for interaction with certain Vbeta elements.

Antigens, Bacterial↗
PubMed1996

Regulation of superantigen-induced T cell activation in the absence and the presence of MHC class II.

To study MHC class II-dependent and -independent SAg2 activation and the relative importance of CD80/CD28 costimulation, staphylococcal enterotoxin A (SEA) was presented to T cells as a fusion protein containing the Fab fragment of an mAb directed against the CA215 glycoprotein. Chinese hamster ovary (CHO) cells transfected with HLA-DR4, CA215, and CD80, individually or in combinations, were used as presenting cells. A strong T cell proliferation was obtained when C215Fab-SEA fusion proteins were presented by CHO-DR/CD80 or CHO-CA215/CD80 double transfectants, whereas only low levels of proliferation were seen in the absence of CD80. Large amounts of IL-2, IFN-gamma, and TNF were produced in addition to an increase in IL-2 mRNA as a result of CD80 costimulation. Only approximately 50% of the SEA-reactive T cells responded by expression of IL-2 receptor chains and by blast formation when activated with SEA in the absence of MHC class II. Reverse transcription-PCR-assisted repertoire analysis of SEA-reactive TCR V beta families showed that the CA215-dependent activation involved an expansion of fewer TCR V beta families compared with MHC class II-dependent activation. One-half of the six analyzed TCR V beta families were expanded independently of class II. This indicates that MHC class II has only a partial influence on the TCR V beta repertoire imprinted by SAg. This finding redefines the role of MHC class II in SAg presentation. It is suggested that MHC class II molecules are selected as SAg-binding molecules mainly as a suitable targeting receptor for professional APC expressing costimulatory molecules such as CD80 and CD86.

Animals↗
PubMed1996

Immune response during tumor therapy with antibody-superantigen fusion proteins.

To engineer superantigens (SAg) to express tumor reactivity, we genetically fused the Fab-part of the tumor-reactive MAb C215 and the bacterial SAg staphylococcal enterotoxin A (SEA). Treatment of mice carrying established lung micrometastases of the C215-transfected syngeneic B16 melanoma with 3-4 daily injections of C215Fab-SEA resulted in strong antitumor effects, while only moderate effects were seen when treatment was given every 4th day (intermittent treatment). High serum levels of IL-2, TNF-alpha, IFN-gamma and strong induction of CTLs (cytotoxic T lymphocytes) were noted after priming with the fusion protein. T cells responded well to 3 daily injections of C215Fab-SEA and then gradually entered a hyporesponsive state, characterized by a reduced ability to produce IL-2, TNF-alpha and IFN-gamma and failure to mediate cytotoxicity in vitro. Intermittent treatment was characterized by increased levels of IL-10, concomitant with accentuated loss of IL-2, TNF-alpha and IFN-gamma production. A 10-fold increase in SEA-reactive TCR V(beta)3+ CD4+ cells was observed in the spleen, while a loss of TCR V(beta)3+ CD8+ and V(beta)11+ CD8+ cells was noted. This is in striking contrast to injections of native SEA which induced a marked deletion of TCR V(beta)3+ CD4+ T cells, but not of CD8+ cells. Recovery of the TH1 cytokine profile occurred within 1-2 weeks, while restoration of cytotoxicity required several months and correlated with recovery of TCR V(beta)3+ CD8+ and TCR V(beta)11+ CD8+ T cells. These results show that the temporal relationship of SAg stimulations dictates the cytokine profile. Moreover, different mechanisms appear to regulate hyporesponsiveness in CD4+ and CD8+ T cells.

Animals↗
PubMed1996

Fusion of a signal sequence to the interleukin-1 beta gene directs the protein from cytoplasmic accumulation to extracellular release.

Interleukin (IL)-1 differs from most other cytokines by the lack of a signal sequence, which results in the retention of the immature proform intracellularly (i.c.). Several cell types have the capacity to produce IL-1, but release has been shown to be restricted predominantly to monocytes/macrophages and associated with apoptosis of the producer cell. These features have limited the studies on IL-1 in early T cell-APC interactions. To develop a model for studying the biological effects of IL-1 beta release during long-lasting immune responses, we have established cells transfected with IL-1 beta cDNA constructs. To construct a hybrid gene for IL-1 beta release, the signal sequence from the related IL-1 receptor antagonist was fused to the gene encoding the 17-kDa mature form of IL-1 beta. A murine fibroblast cell line was transduced with retroviral technique and analyzed for the expression of human IL-1 beta, with or without a signal sequence (ssIL-1 beta and IL-1 beta, respectively). The fibroblasts transduced with either IL-1 beta or ssIL-1 beta expressed similar levels of human IL-1 beta mRNA. High levels of IL-1 bioactivity were recorded in freeze-thaw extracts from cells expressing the IL-1 beta protein i.c., and in supernatants of ssIL-1 beta-transduced cells, which indicates that the initial formation of a proform of IL-1 beta is not required for correct folding of the protein. Treatment of ssIL-1 beta-transduced cells with Brefeldin A (BFA), an inhibitor of protein transport in the endoplasmatic reticulum, induced accumulation of the protein i.c. BFA treatment did not affect IL-1 beta-transduced cells, while lipopolysaccharide-activated human monocytes increased the secretion of IL-1 beta. Cytoplasmic staining of single cells demonstrated that expression of the ssIL-1 beta gene directed the protein to a perinuclear Golgi-like compartment, whereas cells transduced with IL-1 beta cDNA showed a diffuse cytoplasmic distribution pattern. Secretion of IL-1 beta from human monocytes was under certain conditions accompanied by cell death. In contrast, in the fibroblast cell line transduced to secrete IL-1 beta, no accompanying cell death could be detected. Gene targeting of IL-1 to the secretory or cytoplasmic pathway may be useful for elucidating the role of IL-1 in T cell-APC interactions, avoiding cell death of the producer cells.

3T3 Cells↗
PubMed1996

In vivo anergized CD4+ T cells express perturbed AP-1 and NF-kappa B transcription factors.

Anergy is a major mechanism to ensure antigen-specific tolerance in T lymphocytes in the adult. In vivo, anergy has mainly been studied at the cellular level. In this study, we used the T-cell-activating superantigen staphylococcal enterotoxin A (SEA) to investigate molecular mechanisms of T-lymphocyte anergy in vivo. Injection of SEA to adult mice activates CD4+ T cells expressing certain T-cell receptor (TCR) variable region beta-chain families and induces strong and rapid production of interleukin 2 (IL-2). In contrast, repeated injections of SEA cause CD4+ T-cell deletion and anergy in the remaining CD4+ T cells, characterized by reduced expression of IL-2 at mRNA and protein levels. We analyzed expression of AP-1, NF-kappa B, NF-AT, and octamer binding transcription factors, which are known to be involved in the regulation of IL-2 gene promoter activity. Large amounts of AP-1 and NF-kappa B and significant quantities of NF-AT were induced in SEA-activated CD4+ spleen T cells, whereas Oct-1 and Oct-2 DNA binding activity was similar in both resting and activated T cells. In contrast, anergic CD4+ T cells contained severely reduced levels of AP-1 and Fos/Jun-containing NF-AT complexes but expressed significant amounts of NF-kappa B and Oct binding proteins after SEA stimulation. Resolution of the NF-kappa B complex demonstrated predominant expression of p50-p65 heterodimers in activated CD4+ T cells, while anergic cells mainly expressed the transcriptionally inactive p50 homodimer. These alterations of transcription factors are likely to be responsible for repression of IL-2 in anergic T cells.

Adult↗
PubMed1996

Antibody-targeted superantigen therapy induces tumor-infiltrating lymphocytes, excessive cytokine production, and apoptosis in human colon carcinoma.

Bacterial superantigens are the most potent known activators of human T lymphocytes. To engineer superantigens for immunotherapy of human colon carcinoma, the superantigen, staphylococcal enterotoxin A (SEA) was genetically fused to the Fab region of the colon carcinoma-reactive monoclonal antibody C242. In the present study the effector mechanisms involved in the anti-tumor response to C242 Fab-SEA were characterized. Immunohistochemistry and computer-aided image analysis were used in studies of cryopreserved tumor tissue to evaluate the phenotype of infiltrating cells and their cytokine profiles in response to therapy. Human T cells and monocytes were recruited to the tumor area and penetrated the entire tumor mass within hours after injection of C242 Fab-SEA. The production of cytokines at the single-cell level was found to be dominated by tumor necrosis factor (TNF)-alpha, interleukin (IL)-2, IL-4, IL-5, IL-10, IL-12, interferon (IFN)-gamma, granulocyte-macrophage colony-stimulating factor, and transforming growth factor-beta, whereas IL-1-alpha, IL-1ra, IL-1 beta, TNF-beta, IL-3, IL-6, and IL-8 were undetectable. Most of the TNF-alpha, IL-2, IL-12, and IFN-gamma were made by the infiltrating human leukocytes, while the colon carcinoma cells were induced to produce IL-4, IL-10, and TNF-alpha. Up-regulation of IFN-gamma receptors and TNF R p60 receptors was found, while the TNF R p80 receptor was absent. The cytokine production, T cell infiltration, and CD95 Fas receptor expression concomitantly occurred to induce programmed cell death in the tumor cells. This was followed by a strong reduction of the tumor mass that was seen within 24 h after C242 Fab-SEA infusion. These findings demonstrate that antibody-superantigen proteins efficiently recruit tumor-infiltrating lymphocytes actively producing a variety of cytokines likely to be essential for the therapeutic effects observed in the model. Although the humanized SCID model has obvious limitations in its predictive value for treatment of human cancer, we believe that these results encourage clinical evaluation of antibody-targeted superantigens.

Animals↗
PubMed1996

Superantigen-mediated cellular cytotoxicity is dependent on antigen expression, but independent of the P-glycoprotein multidrug resistance phenotype.

Superantigen-activated T cells can be targeted by monoclonal antibodies (mAb) to lyse MHC class II negative tumour cells. In this study we determined the susceptibility of the T-lymphoblastoid leukaemic cell line CCRF-CEM and its multidrug resistant sublines CCRF VCR100, CCRF VCR1000 and CCRF ADR5000 to lysis by monoclonal antibody-targeted and superantigen-activated T cells (superantigen-dependent cellular cytotoxicity, SDCC). A recombinant fusion protein of protein A and the superantigen Staphylococcus enterotoxin A (SEA) was used together with the mAbs anti-CD7, anti-CD38, anti-CD45RA and 4E3 (anti-P-glycoprotein) to correlate susceptibility to SDCC with expression of the MDR1-gene product. Our results demonstrated SDCC to be independent of MDR1-gene expression. This was further confirmed by blocking the function of Pgp in the leukaemic cell lines with a cyclosporine A derivative, which had no influence on SDCC. As expected, expression of the respective cell surface antigens on target cells had a strong impact on SDCC, although other factors seem to influence efficiency of SDCC as well.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1996

The role of monoclonal antibody affinity in tumor immunotherapy evaluated in in vivo models for minimal residual disease.

To evaluate the role of affinity in monoclonal antibody (mAb)-mediated treatment of carcinomas, we compared the antibodies 17-1A and 323/A3 that bind with different affinities overlapping epitopes on the epithelial adhesion molecule Ep-CAM. This comparison was performed in several models for minimal residual disease in mice grafted with Ep-CAM transfected B16 melanoma cells originating from C57BL/6 mice. These cells were either grafted subcutaneously or injected intravenously into nude BALB/c mice, or grafted subcutaneously in immunocompetent C57BL/6 mice. In the BALB/c subcutaneous model, significant therapeutic results (p < 0.05) compared with the control mAb were obtained with both mAbs 17-1A and 323/A3. However, when treating lung metastases in nude BALB/c mice that had developed after intravenous injection of the B16/Ep-CAM tumor cells, only the high-affinity 323/A3 mAb could significantly (p < 0.05) reduce the number of metastases that appeared. In syngeneic C57BL/6 mice grafted subcutaneously with B16/ Ep-CAM cells, a single 323/A3 or 17-1A mAb injection had no effect, in contrast to that observed for the nude BALB/c mouse model. However, multiple injections of the 323/A3 mAb significantly (p < 0.005) reduced the mean tumor volume, although they did not prevent tumor development. The results show that in vivo antibody-mediated effector cell activation and subsequent tumor cell elimination is determined by mAb affinity and target antigen density. Therefore, treatment of minimal residual disease with high-affinity mAb 323/ A3 is expected to improve the clinical results obtained with mAb 17-1A.

Animals↗
PubMed1995

Cross-linking of major histocompatibility complex class II molecules by staphylococcal enterotoxin A superantigen is a requirement for inflammatory cytokine gene expression.

Staphylococcal enterotoxin A (SEA) has two distinct binding sites for major histocompatibility complex (MHC) class II molecules. The aspartic acid located at position 227 (D227) in the COOH terminus of SEA is one of the three residues involved in its interaction with the DR beta chain, whereas the phenylalanine 47 (F47) of the NH2 terminus is critical for its binding to the DR alpha chain. Upon interaction with MHC class II molecules, SEA triggers several cellular events leading to cytokine gene expression. In the present study, we have demonstrated that, contrary to wild-type SEA, stimulation of the THP1 monocytic cell line with SEA mutated at position 47 (SEAF47A) or at position 227 (SEAD227A) failed to induce interleukin 1 beta and tumor necrosis factor-alpha messenger RNA expression. Pretreatment of the cells with a 10-fold excess of either SEAF47A or SEAD227A prevented the increase in cytokine messenger RNA induced by wild-type SEA. However, cross-linking of SEAF47A or SEAD227A bound to MHC class II molecules with F(ab')2 anti-SEA mAb leads to cytokine gene expression, whereas cross-linking with F(ab) fragments had no effect. Taken together, these results indicate that cross-linking of two MHC class II molecules by one single SEA molecule is a requirement for cytokine gene expression.

Antigens, Bacterial↗
PubMed1995

Antibody-targeted superantigens are potent inducers of tumor-infiltrating T lymphocytes in vivo.

Recruitment of antigen-specific tumor-infiltrating lymphocytes (TILs) is a major goal for immunotherapy of malignant tumours. We now describe that T-cell-activating superantigens targeted to a tumor by monoclonal antibodies induced large numbers of pseudospecific TILs and eradication of micrometastases. As a model for tumor micrometastases, syngeneic B16 melanoma cells transfected with the human colon carcinoma antigen C215 were injected intravenously into C57BL/6 mice and therapy with an anti-C215 Fab fragment-staphylococcal enterotoxin A (C215Fab-SEA) fusion protein reacting with the C215 antigen was initiated when visible lung metastases were established. More than 90% reduction of the number of lung metastases was observed when mice carrying 5-day-old established lung metastases were treated with C215Fab-SEA. The antitumor effect of C215Fab-SEA was shown to be T-cell-dependent since no therapeutic effect was seen in T-cell-deficient nude mice. Depletion of T-cell subsets by injection of monoclonal antibody demonstrated that CD8+ cells were the most prominent effector cells although some contribution from CD4+ cells was also noted. C215Fab-SEA treatment induced massive tumor infiltration of CD4+ and CD8+ T cells, while only scattered T cells were observed in untreated tumors. SEA treatment alone induced a slight general inflammatory response in the lung parenchyme, but no specific accumulation of T cells was seen in the tumor. TILs induced by C215Fab-SEA were mainly CD8+ but a substantial number of CD4+ cells were also present. Immunohistochemical analysis showed strong production of the tumoricidal cytokines tumor necrosis factor alpha and interferon gamma in the tumor. Thus, the C215Fab-SEA fusion protein targets effector T lymphocytes to established tumors in vivo and provokes a strong local antitumor immune response.

Animals↗
PubMed1995

Tumor-reactive superantigens suppress tumor growth in humanized SCID mice.

Superantigens are extremely potent activators of T lymphocytes. To develop a tumor-reactive superantigen for cancer therapy, we made a recombinant fusion protein of the superantigen staphylococcal enterotoxin A (SEA) and the Fab region of the C242 monoclonal antibody (C242Fab-SEA), which recognize human colon carcinoma cells. The therapeutic effect of C242Fab-SEA on colon-cancer growth was examined in lymphocyte-engrafted humanized SCID mice bearing intraperitoneally growing Colo205 colon carcinomas. i.v. injections of C242Fab-SEA significantly inhibited tumor growth. The anti-tumor effect required the presence of human T cells in the SCID mice. Optimal therapeutic effects were seen with C242Fab-SEA, but not with C242Fab fragment or SEA alone, demonstrating that both entities of the fusion protein were required. C242Fab-SEA-treated tumors showed a massive infiltration of T cells in the tumor parenchyme, and was accompanied by enhanced expression of ICAM-I and HLA-DR on the tumor cells. The results demonstrate that Fab-SEA fusion proteins convey superantigenicity on tumor cells which evoke T-cell-dependent suppression of tumor growth.

Animals↗
PubMed1995

Costimulation of human CD4+ T cells with LFA-3 and B7 induce distinct effects on AP-1 and NF-kappa B transcription factors.

We have earlier shown that stimulation of human CD4+ T cells with SEA presented on Chinese hamster ovary (CHO)-DR transfectants coexpressing either B7 or LFA-3 resulted in distinct cytokine profiles. We now demonstrate that B7, but not LFA-3, strongly costimulated IL-2 transcription and mRNA expression in CD4+ T cells. Maximal increase in IL-2 transcription was recorded with CHO-DR/B7/LFA-3, suggesting a cooperative effect of B7 and LFA-3 at the transcriptional level. Gel-shift analysis demonstrated that stimulation of CD4+ T cells with CHO-DR and staphylococcal enterotoxin A was sufficient to induce significant amounts of NF-kappa B binding proteins, whereas induction of AP-1 binding proteins required costimulation. LFA-3 induced moderate levels of AP-1, but did not influence the levels of NF-kappa B, while B7 costimulation strongly induced both AP-1 and substantially enhanced NF-kappa B binding proteins. The CHO-DR/B7/LFA-3 triple transfectant induced a further increase in AP-1 and NF-kappa B binding proteins compared with the double transfectants. The level of Oct-1 binding proteins remained similar in all samples. Super-shift analysis revealed that the NF-kappa B complex of costimulated CD4+ T cells contained large amounts of p50, substantial amounts of p65, and marginal levels of c-Rel proteins. The AP-1 binding proteins contained c-Jun, Jun-D, and Fra-1, but marginal amounts of Jun-B and c-Fos. Our results indicate distinct effects of B7 and LFA-3 costimulation on the activity of AP-1 and NF-kappa B. These may partly account for the differential effects of B7 and LFA-3 costimulation on IL-2 expression.

Animals↗
PubMed1995

Crystal structure of the superantigen staphylococcal enterotoxin type A.

Staphylococcal enterotoxins are prototype superantigens characterized by their ability to bind to major histocompatibility complex (MHC) class II molecules and subsequently activate a large fraction of T-lymphocytes. The crystal structure of staphylococcal enterotoxin type A (SEA), a 27 kDa monomeric protein, was determined to 1.9 A resolution with an R-factor of 19.9% by multiple isomorphous replacement. SEA is a two domain protein composed of a beta-barrel and a beta-grasp motif demonstrating the same general structure as staphylococcal enterotoxins SEB and TSST-1. Unique for SEA, however, is a Zn2+ coordination site involved in MHC class II binding. Four amino acids including Ser1, His187, His225 and Asp227 were found to be involved in direct coordination of the metal ion. SEA is the first Zn2+ binding enterotoxin that has been structurally determined.

Binding Sites↗
PubMed1995

Characterization of two distinct MHC class II binding sites in the superantigen staphylococcal enterotoxin A.

Bacterial superantigens (SAgs) are potent activators of T lymphocytes and play a pathophysiological role in Gram-positive septic shock and food poisoning. To characterize potential MHC class II binding sites of the bacterial SAg staphylococcal enterotoxin (SE) A, we performed alanine substitution mutagenesis throughout the C-terminus and at selected sites in the N-terminal domain. Four amino acids in the C-terminus were shown to be involved in MHC class II binding. Three of these amino acids, H225, D227 and H187, had a major influence on MHC class II binding and appeared to be involved in coordination of a Zn2+ ion. Alanine substitution of H225 and D227 resulted in a 1000-fold reduction in MHC class II affinity. Mutation at F47, which is equivalent to the F44 previously shown to be central in the MHC class II binding site of the SAg, SEB, resulted in a 10-fold reduction in MHC class II affinity. The combination of these mutations in the N- and C-terminal sites resulted in a profound loss of activity. The perturbation of MHC class II binding in the various mutants was accompanied by a corresponding loss of ability to induce MHC class II-dependent T cell proliferation and cytotoxicity. All of the SEA mutants were expressed as Fab-SEA fusion proteins and found to retain an intact T cell receptor (TCR) epitope, as determined in a mAb targeted MHC class II-independent T cell cytotoxicity assay.(ABSTRACT TRUNCATED AT 250 WORDS)

Alanine↗
PubMed1995

Superantigen-induced anergy in cytotoxic CD8+ T cells.

This study describes the use of bacterial superantigens to investigate the mechanisms governing peripheral tolerance in CD8+ T cells. Administration of superantigens to mice activates T cells to proliferation, cytokine production, and cytotoxicity, but responding cells subsequently enter a state of hyporesponsiveness or are deleted. Superantigen-induced inactivation has so far mainly been demonstrated for CD4+ T cells. Injection of amounts of the superantigen staphylococcal enterotoxin A (SEA) that are optimal for T cell activation and which induce anergy in CD4+ T cells result in preserved responsiveness in CD8+ CTLs. In contrast, we found that intravenous injection of low concentrations of SEA induced a profound down-regulation of the cytotoxic function in SEA-reactive CD8+ TCR V beta 11+ T cells. No reduction in the number of CD8+V beta 11+ T cells was found, suggesting that anergy and not deletion is the main mechanism for the observed cytotoxic hyporesponsiveness. The cytotoxic anergy was evident 2 days after low-dose priming and remained present 4 wk later, indicating a rapid induction phase and long-lasting persistence. The anergized CD8+ T cell subset expressed lower levels of the alpha-(CD11a) chain of the cell adhesion molecule lymphocyte function-associated Ag 1 (LFA-1) and failed to mediate cytotoxicity, but retained the capacity to proliferate, express IL-2R, produce IFN-gamma, and express granzyme mRNA, which imply a partial defect in TCR-transduced signals. Taken together, these findings suggest that there is a biphasic stimulus-dependent threshold for acquiring responsiveness or anergy in CD8+ T cells.

Animals↗