Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0033036 (APC)
 10,214 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human myoblasts, cultured from muscle and purified to greater than 95%, were investigated for their capacity to act as facultative APC. The myoblasts reacted with antidesmin mAb and had the capacity to fuse into multinucleated myotubes in appropriate medium. The expression of HLA class I, HLA-DR, HLA-DP, HLA-DQ, intercellular adhesion molecule-1 (ICAM-1/CD54), lymphocyte function-associated (LFA) molecules LFA-1 (CD11a/CD18), LFA-2 (CD2), and LFA-3 (CD58) was investigated by FACS analysis before and after induction for various times with human rIFN-gamma, TNF-alpha, or both. Without cytokine induction, myoblasts expressed only HLA-class I and LFA-3. IFN-gamma alone or in combination with TNF-alpha induced the expression of HLA-DR and ICAM-1 reaching a plateau after 48 h, followed by HLA-DP and even later HLA-DQ. TNF-alpha alone induced only ICAM-1. The functional capacity of myoblasts to present Ag to CD4+ T cells was investigated using autologous T cell lines specific for tuberculin, tetanus toxoid, and human myelin basic protein. Noninduced myoblasts or myoblasts treated with TNF-alpha alone could not present any of these Ag to the T cells. However, myoblasts treated with IFN-gamma induced Ag-specific proliferation. In the presence of relevant Ag, myoblasts were killed by the T cells as observed by microscopy and measured by 51Cr release. Ag-specific T cell proliferation and myoblast killing was inhibited in the presence of anti-DR mAb. These results suggest that human myoblasts may act as facultative APC during local immune reactions in muscle.
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PMID:Human myoblasts as antigen-presenting cells. 135 32

The agents cyclosporine, tetranactin (TN), and didemnin B (DB) were compared for their ability to inhibit proliferative human T cell responses in vitro, using anti-CD3, PHA, alloantigen, or tetanus toxoid as stimuli and using monocytes or Langerhans cells as antigen-presenting cells/accessory cells (APC/AC). We found that all three agents suppressed T cell activation in a dose-dependent fashion, irrespective of the stimulus of APC/AC type used. Both T cells and APC/AC were affected by the drugs. DB appeared to be the most potent suppressive drug (IC50 = 1-4 ng/ml), whereas CsA and TN exerted approximately similar potency (IC50 = 50-60 ng/ml). Remarkably however, DB was toxic at a concentration of 10 ng/ml, which is quite close to the inhibition-inducing dose. No toxicity was observed with CsA and TN at doses up to 5000 ng/ml. The agents TN and DB could interrupt ongoing T cell responses and could block responsiveness to exogenous recombinant IL-2. Expression of IL-2 receptors was slightly inhibited by all three drugs. Expression of MHC class II molecule HLA-D and of adhesion molecules LFA-1, LFA-3, and ICAM-1 was clearly reduced by DB, giving an explanation for the observed inhibition of cluster formation between T cells and APC/AC. Except for a slight reduction of LFA-3 by TN, CsA and TN did not affect the expression of any of these cell surface markers or the formation of clusters. Differences in the effects of CsA, TN, and DB on immune responses in vitro and on the phenotype of T cells and APC/AC suggest that these immunosuppressive drugs have different inhibitory mechanisms.
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PMID:A comparison of the inhibitory effects of immunosuppressive agents cyclosporine, tetranactin, and didemnin B on human T cell responses in vitro. 156 53

Monocyte/macrophages (MM) were isolated from HIV-1 seronegative individuals, infected with HIV-1 and examined for their ability to infect autologous T lymphocytes with and without concomitant presentation of exogenous Ag. HIV-1-infected MM presented tetanus toxin (TT) and streptokinase to T cells (as measured by [3H]thymidine incorporation) comparable to presentation by uninfected MM. In these studies, it was observed that HIV-1-infected MM without additional exogenous Ag stimulated autologous T lymphocytes, however, to a lesser degree than with TT and streptokinase. Virus production in T cells appeared to be relative to the degree of stimulation with the highest levels of stimulation and infection observed when T cells were exposed to HIV-1-infected TT-presenting MM. Studies were carried out to examine some of the restricting elements in MM-mediated infection of T lymphocytes with and without TT presentation. Antibodies to CD4, as well as soluble immunopurified gp120, blocked cell-mediated infection indicating that infection of T cells was through the CD4 molecule as has been demonstrated with cell-free virus. In addition, soluble gp120 inhibited Ag presentation by HIV-1-infected and uninfected MM. mAb to MHC class II Ag HLA-DR and -DP blocked T cell infection by HIV-1-infected MM with and without presentation of TT. No effect was observed with mAb to MHC class I Ag. These results indicate that virus transmission to T lymphocytes can be mediated by HIV-1-infected MM and that these cells maintain their function as APC. Activation of T cells appears to be important in the process of T cell infection in this system inasmuch as antibodies that block Ag presentation and thus a T cell proliferative signal inhibit infection.
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PMID:HIV-1 transmission and function of virus-infected monocytes/macrophages. 169 Feb 36

T cell somatic hybrids were obtained by fusion of human tetanus toxoid-specific gamma + delta + T cells and a T cell lymphoma cell line that expresses beta-chain but not alpha-chain transcripts. The hybrids simultaneously and independently expressed alpha beta and gamma delta TCR heterodimers on the cell surface without any significant differences in the level of expression. No heterodimers containing alpha delta-, beta delta-, beta gamma-, and alpha gamma-chains were transported to the cell membrane, indicating a chain specificity in dimer formation. The presence of productively rearranged gamma- and delta-alleles in the hybrid cells and immunoprecipitation of an identical type of TCR-gamma delta from both hybrid and parental gamma + delta + T cells suggests that TCR-gamma delta on the hybrid cells derives from gamma + delta + T cells. Anti-TCR (TCS-delta 1 or WT31) and anti-CD3 antibodies induced a rapid increase in [Ca2+]i in the double-positive hybrids and their variants positive for either the alpha beta or gamma delta complex. Double positive hybrid cells were refractory to stimulation with anti-CD3 antibody after pretreatment with a mixture of anti-TCR-gamma delta and anti-TCR-alpha beta antibodies but not with either antibody alone indicating the functional independence of the two receptors. However, only gamma delta heterodimer receptor was able to respond to tetanus toxoid presented on autologous APC as measured by induction of the p55 chain of IL-2R on stimulated cells.
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PMID:Expression and function of gamma delta- and alpha beta-T cell receptor heterodimers on human somatic T cell hybrids. 169 58

CD4+ T cells require two signals to produce maximal amounts of IL-2, i.e., TCR occupancy and an unidentified APC-derived costimulus. Here we show that this costimulatory signal can be delivered by the T cell molecule CD28. An agonistic anti-CD28 mAb, but not IL-1 and/or IL-6, stimulated T cell proliferation by tetanus toxoid-specific T cells cultured with Ag-pulsed, costimulation-deficient APC. Furthermore, the ability of B cell tumor lines to provide costimulatory signals to purified T cells correlated well with expression of the CD28 ligand B7/BB-1. Finally, like anti-CD28 mAb, autologous human APC appeared to stimulate a cyclosporine A-resistant pathway of T cell activation. Together, these results suggest that the two signals required for IL-2 production by CD4+ T cells can be transduced by the TCR and CD28.
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PMID:CD28 delivers a costimulatory signal involved in antigen-specific IL-2 production by human T cells. 171 61

T cell epitopes can be defined by the use of synthetic peptides, which when added to APC efficiently mimic naturally processed Ag. Free peptide is thought to bind to cell-surface MHC glycoproteins and the TCR then recognizes the resulting complex. The specificity of a tetanus toxin-specific human Th cell clone was investigated using a complete replacement set of peptides in which every amino acid within the minimal T cell epitope was replaced by each of the 19 alternative genetically coded amino acids. Within the minimal epitope, found to be YSYFPSVI (tetanus toxin 593-600), a small number of substitutions could be made without significant loss of activity, defined as substitutions giving peptides whose activity fell within +/- 3 SD of the mean parent response. Y593 could be substituted with F, W, M, L, V, and I; S594 with G and T; Y595, F596, and P597 with no other amino acids; S598 with A; V599 with S, and I600 with L. Rank ordering of the substitutions allowed a precise description to be made of MHC and/or TCR interaction with each amino acid side chain within the epitope. Simplified theoretic calculations based on this study indicate that class II T cell recognition has a specificity greater than 1 in 10(8). Competition experiments indicate that Y595, F596, P597, and I600 are critical for binding of this epitope to its restricting element, HLA DR4Dw14.
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PMID:Role of single amino acids in the recognition of a T cell epitope. 171 63

NK cell clones obtained from three different donors were tested for their ability to present soluble proteins to Ag-specific T cell clones. All NK clones were CD2+CD3-CD56+, whereas the expression of CD16 varied from clone to clone. The NK cell clones were able to process and present tetanus toxoid (TT) to TT-specific T cell clones in a class II HLA restricted manner. The capacity of NK cell clones to function as APC was also observed using the house dust mite allergen Der p I and the Der p I-derived peptide Val89-Cys117. As with EBV-transformed B cell line, NK cell clones could present the peptide 3-13 derived from the 65-kDa heat shock protein of Mycobacterium leprae, but they were unable to present the whole M. leprae Ag. Freshly isolated NK cells, IL-2-activated NK cells, and NK cell lines expanded in vitro could also process and present TT. The ability of the different NK populations to act as accessory cells correlated with their levels of class II HLA expression. These data demonstrate that NK cell clones can efficiently function as APC, however they may be restricted in the types of Ag that they can process.
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PMID:Natural killer cell clones can efficiently process and present protein antigens. 186 Oct 74

Cyclosporin A (CsA) is a widely used agent for the prevention of tissue allograft rejection in human transplantation. As a result of the recent demonstration that the allospecific Th cell response of human PBL can be generated by three distinct pathways of Th cell and APC interactions, we investigated the sensitivity of these three Th-APC pathways, as well as the Th response to recall Ag, to different concentrations of CsA. PBL from healthy volunteer donors were set up as primary in vitro cultures either without antigenic stimulation, or with influenza A virus, tetanus toxoid, or HLA alloantigenic (ALLO) stimulation. Ag-stimulated IL-2 production and proliferation were measured to assess Th cell function. To study the effect of CsA on Th function, different concentrations of CsA (0.001 to 0.1 micrograms/ml final) were added to the cultures at the time of stimulation. Th responses to influenza A virus and tetanus toxoid were more sensitive to CsA than the Th response to ALLO. By selective depletion of either responder or stimulator APC and/or of CD4+ or CD8+ cells, we 1) verified that the human ALLO Th response can be mediated by three distinct Th-APC pathways; 2) demonstrated that the ALLO response mediated by CD4+ Th and self-APC (the same helper pathway used by recall Ag) is as sensitive to CsA as the responses to recall Ag; and 3) showed that there is a hierarchy of sensitivity of these three allospecific pathways. The results are discussed with respect to the potential significance of the differential sensitivity of these allospecific Th-APC pathways to CsA for prevention of tissue allograft rejection.
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PMID:Differential sensitivity of human T helper cell pathways by in vitro exposure to cyclosporin A. 196 47

Lymphokine secretion profiles were studied of human allergen-specific CD4+ T lymphocyte clones (TLC). To this aim, panels of house dust mite Dermatophagoides pteronyssinus (Dp)-specific TLC were generated from two atopic Dp-allergic patients, suffering from severe atopic dermatitis (AD1) and allergic asthma (AD2), respectively, and from a non-atopic individual (NAD). From AD1 additional TLC were cloned specific for tetanus toxoid or Candida albicans, both Ag that were not relevant for the atopic state of this patient. Secretion of IL-2, IL-4, and IFN-gamma was determined after specific stimulation of these TLC, using autologous monocytes as APC. With respect to the production of IL-4 and IFN-gamma, clearly distinct profiles were observed. All Dp-specific TLC from both atopic donors produced IL-4 but not IFN-gamma, whereas the Dp-specific TLC from NAD, as well as the tetanus toxoid- and C. albicans-specific TLC from AD1, all produced IFN-gamma but not or small quantities of IL-4. Most TLC from all panels produced IL-2. These lymphokine profiles were consistent for at least 3 days and were neither dependent on the dose of allergen nor on the atopic or nonatopic state of the donor of APC. The functional consequence of these restricted lymphokine profiles was stressed by the observation that, whereas Dp-specific TLC from AD1 and AD2 supported in vitro IgE production, this support could be abrogated by a Dp-specific TLC from NAD. The present results suggest that CD4+ T lymphocytes that produce IL-4, but not IFN-gamma, occur in high frequencies in the allergen-specific T cell repertoires of atopic donors, which may have important implications for the pathomechanism of atopic disease.
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PMID:Evidence for compartmentalization of functional subsets of CD2+ T lymphocytes in atopic patients. 197 64

The contributions of the amino acids at 13 polymorphic positions in the HLA-DR7 beta 1 chain to T cell recognition of two antigenic peptides of tetanus toxin (p2 and p30) were assessed using transfectants expressing mutant DR7 beta 1 chains as APC for six toxin-specific T cell clones with two different restriction patterns: monogamous (restricted by DR7 only) or promiscuous (restricted by DR7; DR1; DR2, Dw21; and DR4, Dw4). Each of the 13 substitutions significantly decreased or eliminated the ability of the DR7 molecule to present a peptide to one or more of the T cell clones, but none of the substitutions abolished recognition by all clones. Interestingly, substitutions at positions 4 and 25, which are predicted in the class II model to be located outside the peptide binding groove, decreased the ability of the DR7 molecule to present Ag to some clones but not to others. Each of the four clones specific for the p2 peptide and the two clones specific for peptide p30 had a different reactivity pattern to the panel of DR7 beta 1 mutants, indicating that the TCR of each clone has a different view of the p2/DR7 or p30/DR7 complex. These data emphasize the complexity of the interactions of multiple residues in DR7 beta 1 chains in Ag-specific T cell recognition.
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PMID:Antigen-specific T cells with monogamous or promiscuous restriction patterns are sensitive to different HLA-DR beta chain substitutions. 204 Jul 99


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