Defective Antigen Presentation Research Articles

Induction of immune hyporesponsiveness after portal vein immunization with ovalbumin

Background. Previous work has demonstrated prolonged allograft survival after donor-specific portal vein immunization before the transplantation. The purpose of this study was to examine the potential mechanism of portal vein—induced hyporesponsiveness after portal vein immunization with the soluble protein ovalbumin. Methods. Balb/c mice were immunized with a portal vein injection of ovalbumin. After the immunization, in vivo delayed-type hypersensitivity response and in vitro proliferative response of ovalbumin-specific T cells were assessed to determine host immune response. Type 1 (IL-2, IL-12, IFN-γ) and type 2 (IL-4, TGF-β) regulatory cytokines were assessed by semiquantitative reverse transcriptase polymerase chain reaction. Sera anti-ovalbumin IgG, IgG1, and IgG2a were measured by enzyme-linked immunosorbent assay, and the antigen-presenting ability of liver nonparenchymal cells (NPCs) was assessed by T-cell proliferation to ovalbumin in vitro. Results. There was significant inhibition of ovalbumin-specific delayed-type hypersensitivity and T-cell proliferation in portal vein—immunized mice compared with intraperitoneal-immunized or control mice. Reverse transcriptase polymerase chain reaction analysis results showed that lymphocytes from portal vein—immunized mice exhibited decreased type 1 and increased type 2 cytokine messenger RNA expression compared with intraperitoneal-immunized or control animals. The type 2 cytokine response of lymphocytes from ovalbumin portal vein-immunized mice correlated with increased sera ovalbumin-IgG1 and decreased IgG2a. The results of an antigen-presenting assay revealed that liver NPCs were deficient antigen-presenting cells compared with adherent cells from heart or spleen. Conclusions. Processing of ovalbumin by hepatic NPCs results in hyporesponsiveness to ovalbumin by an impaired type 1 cytokine response and a preferential shift toward a type 2 cytokine response, possibly because of defective antigen presentation by hepatic NPCs. Intrahepatic processing of antigen may play an important role in the development of strategies to reduce host immunoreactivity against transplanted allografts. (Surgery 2001;129:66-75.)

Defective antigen presentation resulting from impaired expression of costimulatory molecules in breast cancer

Defective antigen presentation resulting from impaired expression of costimulatory molecules in breast cancer

Altered major histocompatibility complex class II peptide loading in H2-O-deficient mice.

The biosynthesis of MHC class II/peptide complexes involves classical, cell surface MHC products as well as the intracellular component H2-M, required for the removal of invariant chain-derived CLIP and for peptide loading. The function of another intracellular class II heterodimer, H2-O, is the matter of some controversy. The physical association of H2-O with H2-M and co-localization in class II+ vesicles suggest a related function in peptide exchange. Furthermore, the distinctive thymic distribution of H2-O raises the possibility of a specialized role in T cell thymic selection. To investigate the role of H2-O in vivo we generated mice carrying a targeted disruption in the H2-Oa gene. No evidence was obtained for a defect in removal of CLIP. However, the array of endogenous peptides bound by class II was altered and a defect in antigen presentation through H2-A to T cells was seen on the 129/Sv/ C57BL/6 mixed strain background but not in 129/Sv pure strain mice. Furthermore, H2-O-null mice showed enhanced selection of CD4+ single positive thymocytes. The findings indicate that H2-O interacts with H2-M in peptide editing but that the genetic background in which H2-O deficiency is manifest is also important. Overall, the experiments indicate that H2-O/HLA-DO should be regarded as neither up-regulating nor down-regulating the DM-dependent release of CLIP, but as a modulator of peptide editing, determining the presenting cell type specific peptide profile able to retain stability in the class II groove.

Increasing the frequency of T-cell precursors specific for a cryptic epitope of hen-egg lysozyme converts it to an immunodominant epitope.

Efforts to understand the mechanisms that govern how immunodominant T-cell epitopes are selected from protein antigens have focused mostly on differences in the efficiency of processing and presentation of peptide/major histocompatibility complex (MHC) complexes by antigen-presenting cells, while little attention has been directed at the role of the T-cell repertoire. In this report, the influence of the T-cell repertoire on immunodominance was investigated using transgenic mice that express the beta chain from a T-cell receptor specific for a cryptic Ek restricted epitope of hen-egg lysozyme, HEL85-96. In these mice, the frequency of HEL85-96-specific T-cell precursors is increased 10-20-fold over non-transgenic mice. Transgenic mice respond as well as non-transgenic controls to intact HEL, even though they respond poorly or not at all to a variety of other antigens, including the dominant H-2k restricted epitopes of HEL. Following immunization with native HEL, the only HEL peptide that could recall a response in vitro in the transgenic mice was HEL85-96. Therefore, this normally cryptic epitope is the sole immunodominant epitope in the transgenic mice, and this alteration in immune response is due solely to an increase in the frequency of specific T-cell precursors. An analysis of four additional H-2k restricted cryptic epitopes of HEL suggests that three are similarly limited by T-cell frequency, and that only one is consistent with a defect in efficient antigen presentation. This indicates that there are at least two different types of cryptic epitopes, one in which crypticity is caused by inefficient processing or presentation, and another in which the frequency of specific T-cell progenitors is limiting.

Activation of lymphocytes by anti-CD3 single-chain antibody dimers expressed on the plasma membrane of tumor cells.

Activation of cytotoxic T cells without MHC restriction was attempted by expressing single-chain antibodies (scFv) against CD3 on the surface of tumor cells. A chimeric protein consisting of a scFv of mAb 145.2C11, the hinge-CH2-CH3 region of human IgG1, and the transmembrane and cytosolic domains of murine CD80 formed disulfide-linked dimers on the plasma membrane of cells and specifically bound lymphocytes. Anti-CD3 scFv dimers expressed on the cell surface induced CD25 (IL-2 receptor alpha-chain) expression and proliferation of splenocytes. CT26 tumor cells engineered to express surface scFv dimers (CT26/2C11) also induced potent lymphocyte cytotoxicity with or without addition of exogenous IL-2. Splenocytes activated by CT26/2C11 cells also killed wild-type CT26 cells, indicating that activated splenocytes could kill bystander tumor cells. Immunization of BALB/c mice with irradiated CT26/2C11 cells did not protect against a lethal challenge of CT26 cells, suggesting that systemic immunity was not induced. However, the growth of CT26 tumors containing 50% CT26/2C11 cells was significantly retarded compared with CT26 tumors, whereas CT26/2C11 tumors did not grow in syngeneic mice. These results suggest that expression of anti-CD3 scFv dimers on tumors may form the basis for a novel therapeutic strategy for tumors that exhibit defects in antigen processing or presentation. Gene Therapy (2000) 7, 339-347.

The effect of a vitamin A acetate diet on ultraviolet radiation-induced immune suppression as measured by contact hypersensitivity in mice.

The adverse health effects caused by increased exposure to ultraviolet radiation (UVR) due to deterioration of stratospheric ozone are of major concern. These health effects include sunburn, skin cancer, cataracts and immune suppression. Immune suppression has been associated with the release of cytokines, a defect in antigen presentation, induction of suppressor T cells and suppression of contact hypersensitivity (CH). CH is typically assessed by the mouse ear swelling test (MEST). Previous studies have demonstrated enhanced CH responses with vitamin A acetate (VAA) dietary supplementation assessed by MEST and the local lymph node assay (LLNA). To determine the effect that VAA has on UVR-induced immune suppression, we examined both the induction and elicitation phases of CH using murine models. The MEST was used to evaluate the interaction of UVR and VAA on CH elicitation. However, a positive MEST response requires that the induction phase as well as the elicitation phase of CH be functional. The LLNA was used to evaluate the interaction of UVR and VAA only on CH induction. We tested the hypothesis that mice maintained on a VAA-enriched diet are more resistant to UVR-induced immune suppression (CH) than those maintained on a control diet. Mice were maintained on a VAA-enriched or the control diet for 3 weeks and then exposed to UVR 3 days prior to sensitization with 2,4-dinitrofluorobenzene (DNFB). VAA enhanced the MEST response in both UVR-exposed and non-UVR-exposed mice. The VAA-enriched diet did not significantly alter the LLNA response in either UVR- or non-UVR-exposed mice. However, there was significant suppression in CH by UVR as measured by the LLNA. These results indicate that (1) the VAA-enriched diet does not restore the number of proliferating cells in the CH induction phase of UVR-induced immunosuppression; (2) the immunosuppressive effects of UVR affect the induction phase of CH; and (3) the LLNA should be examined as an alternative to the MEST for measurement of UVR-induced immunosuppression. The data indicate that the VAA-enriched diet enhanced the elicitation response (MEST) but not the earlier induction phase (LLNA). Further studies are necessary to define mechanisms of action, but modulation of cytokines and effects of specific lymphocyte subsets, as well as systemic effects and local modulation at the site of elicitation are possible. Additionally, future studies to evaluate the effect of the VAA-enriched diet when multiple doses of both UVR and DNFB are used would be of interest for both the LLNA and MEST end-points.

Defective antigen presentation resulting from impaired expression of costimulatory molecules in breast cancer

Previous experiments from our laboratory have shown that immune mechanisms aiming at the destruction of tumour cells including the recognition of target cells and their elimination via the expression of intercellular adhesion molecule-1 (ICAM-1; CD54), the production of tumour necrosis factor-alpha (TNF-alpha) by monocytes and appropriate function of lymphocyte subpopulations were defective in breast cancer. Previous observations were extended to assess expression levels and regulatory mechanisms of costimulatory molecules CD54, CD80 and CD86 on monocytes derived from patients with early breast cancer (EBC). In addition, antigen presentation by antigen-presenting cells (APC) was analyzed within this context. We report that monocytes derived from patients with EBC exhibited significantly decreased expression levels of CD54 (p = 0.0002), CD80 (p = 0.009) and CD 86 (p = 0.002) compared with monocytes derived from healthy females. Simultaneously, lipopolysaccharide (LPS)-induced TNF-alpha production of monocytes was found to be defective in patients with EBC. Finally, T-cell proliferation in response to tetanus toxoid (TT) was significantly decreased in patients with EBC compared with healthy control females (p < 0.0001). Furthermore, T-cell proliferation in response to TT-pulsed APC derived from healthy controls was significantly inhibited in the presence of anti-CD54 and/or anti-CD80 antibodies in a dose-dependent manner, thus corroborating the necessity of the presence of CD54 and CD80 as costimulatory molecules in the present setting. We conclude that monocytes derived from patients with EBC showed a simultaneous defect of expression of CD54 and its regulation via TNF-alpha, CD80 and CD86 as well as T-cell proliferation following exposure to TT-pulsed APC. Based upon these findings, it is speculated that defects in costimulatory molecule expression might contribute to tolerance of the immune system towards the presence of malignant cells in patients with EBC.

Immune rejection of intracerebral gliomas using lymphocytes from glioma-bearing rats.

Naturally occurring malignancies do not induce immune responses against cancer antigens. Is the lack of an immune response caused by an antigen presentation defect or by induced antigen-specific immune suppression? The current study was performed to determine whether a progressing intracerebral malignancy affects production of peripheral autologous glioma antigen-specific immune responses. Peripheral immunization of both glioma-bearing and non-glioma-bearing animals with cancer cells and adjuvant generated similar levels of glioma antigen-specific cytotoxic T lymphocyte activity. However, immune cell populations from glioma bearers were significantly less efficient than immune cell populations from non-cancer bearers in their ability to reject progressing intracerebral tumors. A variety of manipulations designed to reduce nonspecific immune suppression in vivo and in vitro had no effect on the in vivo efficacy of the activated T-lymphocyte populations. The presence of progressing tumors appeared to augment rather than suppress cancer antigen-specific responses, leading to the speculation that reduced efficacy was caused not by generalized immune suppression but rather by a reduction in the number of immune effector cells by either clonal anergy or clonal deletion. Most importantly, the data demonstrated that, despite decreased in vivo efficacy, immune effector cells capable of rejecting an intracerebral malignancy could be generated from cancerous hosts.

An algorithm for evaluating human cytotoxic T lymphocyte responses to candidate AIDS vaccines.

Development of an effective vaccine against HIV-1 will likely require the induction of a broad array of immune responses, including virus-specific CTLs and neutralizing antibodies. One promising vaccine approach involves live recombinant canarypox (CP)-based vectors (ALVAC) containing multiple HIV-1 genes. In phase I clinical trials in HIV-1-seronegative volunteers, the cumulative rate of detection of HIV-1-specific CTLs has been as high as 60-70%. In the present study, the factors associated with CTL responsiveness were evaluated in a subset of vaccinees immunized with a CP vector expressing portions of the gag, pro, and env genes of HIV-1 (ALVAC-HIV). CTL responses were detected in one of seven examined. While the responding individual had both CD4+ and CD8+ CTLs directed at multiple HIV-1 antigens, this response was not detectable 1 year after the last vaccination. In-depth characterization of "CTL nonresponders" showed that nonresponsiveness was not associated with defects in antigen processing or presentation. A generalized defect in CTL responsiveness was ruled out by parallel assays to detect CMV-specific CTLs from these same volunteers. Furthermore, HIV-1-specific memory CTLs were not detectable by peptide stimulation or by a novel technique for flow cytometric visualization of Gag epitope-specific T lymphocytes while HIV-1-seropositive donors frequently had 0.1-3% of CD8+ cells stain positively for this epitope (SLYNTVATL). Taken together, these results suggest that the lack of detectable HIV-1 CTLs in these volunteers was not due to classic MHC-linked nonresponsiveness.

Elucidation of the genetic basis of the antigen presentation defects in the mutant cell line .220 reveals polymorphism and alternative splicing of the tapasin gene.

Antigenic peptides are presented to cytotoxic T lymphocytes by heterodimers of MHC class I molecules and beta2-microglobulin. Peptides are generated in the cytosol and translocated into the endoplasmic reticulum (ER) through the transporter associated with antigen processing (TAP). Optimal binding of peptides to class I molecules is facilitated by the physical association between class I heterodimers and TAP. This association is mediated largely by the glycoprotein tapasin. Analysis of tapasin function has relied on a mutant cell line, .220, which is defective in tapasin expression and antigen presentation. We have investigated the genetic basis of these defects. In .220 cells, Tapasin transcripts lack exon two. This is caused by a single nucleotide substitution, disrupting the 5' splice site of the second intron. A tapasin protein is produced in .220 cells, but has a truncated signal peptide and lacks the N-terminal 49 amino acids encoded by full-length transcripts. Nonetheless, this truncated form is translocated into the ER and interacts with TAP. As a result of alternative splicing, transcripts lacking exon two are also present in wild-type cells, although no truncated protein was detected. Additionally we describe a polymorphism in the Tapasin gene, with two alleles encoding arginine or threonine at peptide position 240.

Hsp72-mediated augmentation of MHC class I surface expression and endogenous antigen presentation.

Efficient recognition of tumor cells by cytolytic T lymphocytes (CTL) is often dependent on the presentation of cytosolic peptides in the context of MHC class I molecules. This process may be influenced by various molecular chaperones. To analyze this influence, we have utilized B16 melanoma cells, which are not effectively recognized by MHC class I-restricted CTL. This resistance to CTL is apparently due to a very low level of surface MHC expression. We have found that stably transfected clones of B16 which constitutively express the human heat shock protein 72 (Hsp72) exhibit significantly increased levels of MHC class I antigens on their surface. This Hsp72-mediated up-regulation of surface MHC class I antigen represents an increase in the amount of functional MHC-peptide complexes as measured by conformation-dependent antibodies and recognition by MHC class I-restricted CTL. Expression of Hsp72 did not improve the antigen presentation defect in cells lacking the activity of the transporter associated with antigen presentation (TAP). Moreover, mice immunized with Hsp72-expressing B16 cells, but not with control-transfected B16 cells, display significantly increased resistance to a subsequent challenge with live, wild-type B16. Together, our data demonstrate that the immune recognition of tumor cells can be substantially enhanced by the suitable expression of a molecular chaperone.

Low CD83, but normal MHC class II and costimulatory molecule expression, on spleen dendritic cells from HIV+ patients.

Dendritic cells (DCs), which are the most potent antigen-presenting cells for T lymphocytes, are targets for HIV in vitro and in vivo. Antigen presentation by DCs has been suggested to be impaired during HIV infection; however, the extent to which DCs from HIV+ individuals are altered, particularly in lymphoid organs where T cell stimulation takes place, is not clear. To address this question, the levels of expression of functionally important molecules by spleen DCs from HIV+ patients (n = 6), and HIV- organ donors (n = 5) were compared. By rare event analysis of flow cytometry data, spleen DCs from HIV+ patients were not depleted, representing 0.6 +/- 0.4% of spleen mononuclear cells compared with 0.8 +/- 0.5% in HIV- spleens. Fresh HIV+ spleen DCs were MHC II+ and weakly CD86+CD40+, but negative for CD83 and CD80, and hence had a normal phenotype, showing no signs of in vivo activation. After 24 hr of culture, they upregulated the expression of MHC II, CD40, CD80, and CD86 to levels just as high as those on DCs from organ transplant donors. However, cultured DCs from HIV+ spleens showed lower expression of CD83, compared with DCs from HIV- spleens. The biological significance of this observation will be appreciated further when the function of this molecule is better known. These results suggest that putative defects in antigen presentation by DCs from HIV+ patients are not related to the surface expression of MHC II, CD40, CD80, or CD86.

Skin-derived IL-10 following acute, low dose ultraviolet-B radiation creates a systemic antigen presentation defect

Skin-derived IL-10 following acute, low dose ultraviolet-B radiation creates a systemic antigen presentation defect

Trauma-induced alterations in macrophage function

Background: The juxtaposition of immune suppression and a hyperactive inflammatory response after injury represents a paradox in immune function. The aim of this study was to evaluate the delayed macrophage hypersecretion of inflammatory mediators in relation to functional macrophage defects. Methods: BALB/c mice were randomized to control or trauma (femur fracture plus 40% blood volume hemorrhage) groups. One and 7 days after injury, splenic macrophages were isolated and assayed for antigen presentation and the production of inflammatory mediators tumor necrosis factor-α (TNF-α), interleukin (IL)-6, prostaglandin E 2, H 20 2, and nitric oxide. Results: One day after injury, there were significantly diminished macrophage antigen presentation and decreased mean production of TNF-α, IL-6, and H 20 2. In contrast, 7 days after injury, splenic macrophages produced significantly increased mean amounts of TNF-α, IL-6, prostaglandin E 2, H 20 2, and nitric oxide, with a persistent functional defect in antigen presentation. Conclusions: This phasic response to trauma suggests a persistent state of macrophage dysregulation that may help explain the paradox of immune suppression, manifested by functional defects predisposing patients to increased infections, in the setting of inflammatory mediator hypersecretion, predisposing patients to the systemic inflammatory response syndrome/multiple organ dysfunction syndrome. (Surgery 1998;123:96-101.)

Defect in Th1-Like Cells of Nonresponders to Hepatitis B Vaccine

ABSTRACT: Peripheral blood lymphocytes from nonresponders to hepatitis B vaccine (HBsAg) failed to undergo a proliferative response to recombinant HBsAg in vitro, whereas cells from responders proliferated vigorously. The lack of proliferative response was not due to defective antigen presentation in that MHC-identical responder and nonresponder antigen presenting cells were equally effective in stimulating responder T cells. Nonresponder T cells did not proliferate in response to antigen-pulsed MHC identical responder antigen presenting cells. The present study demonstrated that: 1) there were no detectable (1 in <20 × 10 4) HBsAg-precursor T cells in any of the nonresponders, while in responders the frequency of HBsAg-precursor T cells ranged from 1 in 3.2 × 10 3 to 1 in 40 × 10 3; 2) nonresponder cell cultures did not secrete IL-2 in response to HBsAg stimulation; 3) exogenous recombinant IL-2 did not restore the proliferative response of the T cells in HBsAg-pulsed cultures of nonresponders. These results suggest that the cellular basis for the lack of response to HBsAg is a defect in HBsAg-specific Th1-like cells; either there is an absence of the Th1 cells or cells with TCR specificity for HBsAg are present but are unresponsive to the HBsAg peptide-MHC complex ( i.e., anergy or tolerance).

Proteasome specificity correlates with defective antigen presentation in Burkitt's lymphoma cells

Proteasome specificity correlates with defective antigen presentation in Burkitt's lymphoma cells

Proteasome specificity correlates with defective antigen presentation in Burkitt's lymphoma cells

Proteasome specificity correlates with defective antigen presentation in Burkitt's lymphoma cells

Transforming growth factor β induced immune deviation is associated with defective monocytic antigen presenting capacity

Transforming growth factor β induced immune deviation is associated with defective monocytic antigen presenting capacity

Transforming growth factor β induced immune deviation is associated with defective monocytic antigen presenting capacity

Transforming growth factor β induced immune deviation is associated with defective monocytic antigen presenting capacity

Bone marrow-derived dendritic cells, infection with human immunodeficiency virus, and immunopathology.

Dendritic cells (DC) exposed to HIV-1 show nonproductive infection that may become productive as they mature. The distribution of DC within genital mucosa and their susceptibility to infection particularly with clade E viruses could be reflected in the ease of heterosexual transmission. Carriage of virus and viral antigen by DC into lymph nodes may allow clustering and activation of T cells and production of protective immune responses. However, secondary infection of activated T cells from infected DC could cause dissemination of virus and loss of infected DC and T cells. In asymptomatic infection, fewer dendritic cells with reduced capacity to stimulate CD4 T cell proliferation are found before evidence of T cell abnormalities, and these early changes in antigen-presenting cells may result in a decline in the production of CD4 memory T cells. However, DC fuel ongoing production of antibody to HIV-1. Signaling by DC to T cells may thus underlie two major features of early HIV infection--loss in CD4+ memory T cells and persistence of antibody production. In AIDS, infected dendritic and epithelial cells within the thymus may affect maturation and contribute to loss of the "naive" T cell population. Further loss of memory T cells may occur through syncytium formation with infected DC. Finally, in AIDS patients, there is a failure in the development and the function of DC from CD34+ stem cells. In conclusion, the infection of dendritic cells, loss in their numbers, and changed signaling to T cells may shape the pattern of immunity during infection with HIV-1. Conversely, treatments that reverse the defect in antigen presentation by DC may improve cell-mediated immunity.