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

Lymph node cells from 4-wk-old MRL/Mp-lpr/lpr mice, but not from MRL/Mp-+/+ mice, when cultured in vitro for 5 to 7 days, will spontaneously proliferate and produce IL-2. We examined the expression of several cell surface Ag on lymph node cells from MRL/Mp-lpr/lpr mice before and after in vitro culture. There is an increase in the expression of Thy-1, L3T4, IL-2R, T cell activating protein, T cell receptor, and T3 complex on the surface of cultured cells. Cultured cells produced IL-3, IFN-gamma, and small but detectable amounts of IL-1 in addition to IL-2. Gamma irradiation of APC from young MRL/Mp-lpr/lpr mice or treatment of APC with a mAb (J11D) and C, completely abrogated their stimulatory capacity. These experiments suggest that B cells are the predominant APC responsible in the activation of autoreactive T cells in MRL/Mp-lpr/lpr mice. Lymph node cells from C57BL/6-lpr/lpr or C3H-lpr/lpr mice were unable to spontaneously proliferate or produce IL-2. Lymph node cells from (MRL/Mp-lpr/lpr x C57BL/6-lpr/lpr) F1 mice or (C3H-lpr/lpr x MRL/Mp-lpr/lpr) F1 mice did proliferate and produced IL-2 after in vitro culture. Using T cells from these F1 animals and APC from each parental haplotype, we found that APC from MRL/Mp-lpr/lpr mice induced more proliferation and greater amounts of IL-2, when compared to APC from F1 animals. APC from C57BL6-lpr/lpr mice or C3H-lpr/lpr were unable to induce spontaneous proliferation and IL-2 production. Therefore, B cells from MRL/Mp-lpr/lpr mice appear to possess unique features that enable them to activate autoreactive T cells more effectively than B cells from other mice bearing the lpr/lpr gene.
 ...
PMID:Autoreactive T cells in MRL/Mpr-lpr/lpr mice. Characterization of the lymphokines produced and analysis of antigen-presenting cells required. 313 46

Purified peripheral blood T lymphocytes and the CD8-CD4+ and CD4-CD8+ T cell subsets, exhaustively depleted of APC have been studied for their capacity to respond to mAb directed against the CD3-Ti Ag-specific TCR complex and against the CD2 SRBCR. It is demonstrated that high affinity IL-2R can be readily induced by either anti-CD3 and/or anti-CD2 stimulation. However, IL-2 production can be observed only in the CD4+CD8- T cell subset. These results clearly contrast data obtained with purified CD4-CD8+ T cells, which are able to proliferate when the CD3-Ti complex is activated in the presence of APC. The data presented in the present study demonstrate that a simplified model for T cell activation and clonal expansion of the two major T cell subsets involve only the CD3-Ti complex and the CD2 Ag. Under conditions where the activation signals for the T cells are restricted only to the activation of CD3-Ti and CD2, the CD4+CD8- T cells respond with IL-2 production and expression of high affinity IL-2R, whereas the CD4-CD8+ T cell subset depends on exogenous IL-2 provided by the CD4+CD8- cells. These data do not, however, exclude an involvement of other cell-surface signals for regulation and control of T cell activation and T cell effector functions.
 ...
PMID:Differential in vitro activation of CD8-CD4+ and CD4-CD8+ T lymphocytes by combinations of anti-CD2 and anti-CD3 antibodies. 325 28

It has been previously reported that Ia Ag on APC seems to be involved in Ag-specific T cell activation in at least two different ways: one is to associate with foreign Ag to form a neoantigenic determinant (the Ag-specific Ia function), and the second is to interact with T cells in a non-Ag-specific manner. Both Ia functions are required for T cell activation. In the present study we examined whether the T cell structures responsible for the non-Ag-specific Ia interaction were separable from the Ag-specific alpha/beta TCR. Purified protein derivative of tuberculin (PPD)-specific murine hybridoma T cells and polyclonal lymph node T cells were stimulated for IL-2 production by APC pulsed with PPD, glutaraldehyde fixed, and anti-Ia antibody treated, to provide the antigenic PPD/Ia determinant, in the presence of glutaraldehyde-fixed non-Ag-pulsed APC, to provide the non-Ag-specific Ia interactions. However, in several different approaches the T cell structures or activation signals responsible for the Ag-specific recognition and non-Ag-specific Ia interactions seemed to be associated with each other in this experimental system. First, the Ag-specific and non-Ag-specific Ia interactions with T cells were both required simultaneously to initiate T cell activation, and it was not possible to activate T cells by providing either Ia signal subsequent to the other. Second, the T cell structures responsible for the non-Ag-specific Ia interactions appeared to be clonally distributed in PPD-specific lymph node T cells. Third, another T cell hybridoma specific for bovine insulin also showed dual Ia interactions, but the specificity of the non-Ag-specific Ia function was different than that for the PPD-specific T cell response. Fourth, all subclones of PPD-specific T hybridomas that had lost Ag-specific responsiveness also lost functional non-Ag-specific Ia interactions. Taken together, these observations suggest that a single species of TCR may mediate both the Ag-specific and non-Ag-specific Ia interactions. In addition, the non-Ag-specific Ia interaction with T cells augmented the Ag-specific Ia interaction for T cell activation, indicating that both types of interactions may be involved in some T cell responses. Based on these observations, a Velcromodel depicting the synergy between the two Ia functions is proposed in which a matrix of interactions consisting of higher affinity Ag binding and lower affinity Ia-TCR associations provides cooperative sets of signals necessary for cellular activation.
 ...
PMID:Two roles for Ia in antigen-specific T cell activation. II. Toward a Velcro model of antigen recognition. 325 11

Ag recognition of Lyt-2 (CD8)-positive T lymphocytes requires the presentation by APC of a suitably processed Ag in association with MHC class I molecules. In previous studies we have obtained evidence that, for optimal activation, both the alpha beta-TCR and Lyt-2 have to participate in this recognition process. In the current study we investigate the functional consequences of limited cross-linking of these cell surface molecules by using soluble, dimeric hetero- and homoconjugates of mAb to Lyt-2 and to the TCR beta-chain (F23.1). Heterologous cross-linking of Lyt-2 to the TCR induced a vigorous, selective Lyt-2+ T cell proliferative response. Functionally active cytotoxic cells were generated, and a high frequency of responding cells was observed in limiting dilution analyses. In contrast, homologous TCR cross-linking initiated a less pronounced proliferation with a relatively low frequency of response, whereas Lyt-2 cross-linking resulted in no cellular proliferation. Significant T cell activation occurred with exposure to anti-Lyt-2: F23.1 mAb dimers at concentrations an order of magnitude lower than those required for stimulation by F23.1:F23.1 mAb dimers. The induction of proliferation by mAb dimers occurred in the absence of Fc components and in rigorously APC depleted, purified T cell preparations. Effective stimulation of resting T cells could be induced also by heterodimers of monovalent Fab fragments. Heterologous cross-linking of Lyt-2 to the TCR was superior to homologous TCR cross-linking primarily with respect to proliferation in IL-2 containing media and to IL-2R expression, whereas proliferation in response to other lymphokines and the production of IL-2 itself were similar under both cross-linking regimens. Thus, when linked to the TCR, Lyt-2 contributed a strong, positive signal toward IL-2-dependent growth of resting T cells. We assume that in the case of Ag-driven T cell activation, the class I MHC molecule acts as the physiologic cross-linking ligand for Lyt-2 and the TCR.
 ...
PMID:Heterologous cross-linking of Lyt-2 (CD8) to the alpha beta-T cell receptor is more effective in T cell activation than homologous alpha beta-T cell receptor cross-linking. 326 71

Using B cells as APC, antigen specific responses of two murine T cell clones, 34-7F and 35-8H, were analyzed. 34-7F cells produced IL-2 but failed to proliferate, whereas 35-8H cells both produced IL-2 and proliferate. The antigenic stimulation increased intracellular free Ca2+ concentration in both clones, but enhanced inositol phospholipid metabolism only in 35-8H cells. The treatment of 34-7F cells with PMA, an activator of protein kinase C, synergized with the antigenic stimulation to induce the proliferation of the T cells. Thus, the failure of 34-7F cells to proliferate in the Ag response appears to result from the absence of an increase in inositol phospholipid metabolism. The absence is likely due to the defect in B cells as APC, inasmuch as the antigenic stimulation of 34-7F cells with whole spleen cells induced increases in inositol phospholipid metabolism and proliferation. The PMA treatment synergized with the Ag on B cells to enhance IL-2R expression, which was not inhibited by the addition of nifedipine, a calcium channel blocker. The agent inhibited the IL-2 production. Taken together, the results in the present experiments suggest the association of IL-2 production with increases in intracellular free Ca2+ concentration but not in inositol phospholipid metabolism, and that of IL-2R expression with increases in the metabolism but not in intracellular free Ca2+ concentration.
 ...
PMID:Molecular analysis of the dissociation between IL-2 production and proliferation in a response of a T cell clone to the antigen presented by B cells. 326 19

The effect of eight microbial protease inhibitors on Ag-presentation to six different Ag-specific T cell clones was investigated. We found that these protease inhibitors can inhibit Ag presentation in a highly selective manner. This selectivity was evident with T cell clones specific to different Ag as well as with T cells specific to the same Ag but differing in their H-2 restriction. The inhibition was to due to cytotoxicity or effects through the TCR because none of the eight inhibitors inhibited IL-2-induced T cell proliferation, and because they did not inhibit Ag presentation by fixed APC or synthetic polypeptide. The conclusion after these data suggests that each specific antigenic fragment is produced by a unique set of proteases.
 ...
PMID:Selective inhibition of antigen presentation to cloned T cells by protease inhibitors. 326 20

In order to clarify the nature of the defect in the process of antigen presentation caused by uv radiation, low-density spleen cells were used as a potent APC source in a hapten-specific cytolytic T-cell (Tc) system. It was demonstrated that IA+ weakly adherent low-density spleen cells, when directly coupled with azobenzene arsonate (ABA), led to the activation ABA-specific Tc. When these APC were exposed to uv radiation (12 J/m2/sec) for 30 sec, their ability to lead to Tc activation was markedly inhibited. The defect imposed by uv radiation could be specifically bypassed by the addition of small amounts of homogeneous IL-1 or IL-2. This led to the specific activation of ABA-reactive H-2-restricted Tc. The purified IL-1 was also found to bypass the systemic defect imposed in vivo by external uv radiation of mice. This may indicate a potential therapeutic role for IL-1.
 ...
PMID:Molecular signals in antigen presentation. I. Effects of interleukin 1 and 2 on radiation-treated antigen-presenting cells in vivo and in vitro. 660 25

Because UV-induced epidermal macrophages (UV-Mph) preferentially activate CD4+ T suppressor-inducer cells and induce tolerance, we hypothesized that they differentially up-regulate T cell early activation genes compared with constitutive epidermal APC, Langerhans cells. We used epidermal cells from UV-exposed (UV-EC) and control (C-EC) human skin to stimulate allogeneic CD4+ T lymphocytes. Reverse transcriptase-PCR revealed that both C-EC (Langerhans cells) and UV-EC (UV-Mph) induced 10(3)- to 10(6)-fold increases in IL-2 mRNA. However, while T cells stimulated by C-EC for 48 h showed a greater than 10(3)-fold increase in IL-2R alpha mRNA, those stimulated by UV-EC did not (n = 5, p = 0.004). Flow cytometry demonstrated that 4.1 +/- 2.3% of unstimulated CD4+ lymphocytes expressed cell surface IL-2R alpha, which increased to 15.7 +/- 1.8% upon stimulation by C-EC for 48 h, but stimulation by UV-EC failed to increase the IL-2R alpha+ population (n = 3, p = 0.038). The addition of neutralizing anti-TGF-beta Abs to UV-EC-stimulated cultures restored CD4+ cell surface IL-2R alpha expression to 12.9 +/- 0.2%. CD4+ T cell activation by UV-Mph is distinct from previously described models of tolerance such as Th2 activation (IFN-gamma mRNA was induced and IL-4 mRNA was not) and Th1 anergy (IL-2 mRNA levels induced by UV-EC and C-EC were similar). Furthermore, costimulatory signals were provided by UV-Mph; CTLA4-Ig and LFA-3-Ig fusion proteins and Abs to CD2, LFA-3, LFA-1, and ICAM-1 inhibited UV-Mph-induced T cell proliferation. Thus, the altered immune outcome induced by UV-Mph (tolerization) compared with Langerhans cells (sensitization) is reflected as a novel mechanism of initial CD4+ T cell early activation gene expression characterized by TGF-beta-dependent deficient IL-2R alpha expression.
 ...
PMID:Suppressor T cell-activating macrophages in ultraviolet-irradiated human skin induce a novel, TGF-beta-dependent form of T cell activation characterized by deficient IL-2r alpha expression. 749 43

Resting CD4+T cells must receive nonspecific costimulatory signals from APC to produce maximal amounts of IL-2 in response to TCR signaling. The T cell-specific surface molecule CD28 is one protein that transduces a costimulatory signal following interaction with its ligand B7. We report here the identification of another contact-mediated costimulatory signal provided by the human histiocytic line U937 and by purified monocytes. Although this monocyte-derived costimulus is not transduced by the CD28/B7 interaction, it synergizes with the CD28 signal to elicit maximal IL-2 production from freshly isolated T cells. IL-2 production by previously activated CD8+ T cells depends on the monocyte-derived costimulatory signal, although memory CD4+ T cells respond well to either the monocyte-derived costimulus or B7-derived costimulation. In contrast, IL-2 secretion by naive T cells appears to require the synergistic interaction between both costimulatory pathways. These results suggest that the array of costimulatory ligands expressed by various APC affects the magnitude of the T cell response and also which T cell subsets are stimulated.
 ...
PMID:Monocytes provide a novel costimulatory signal to T cells that is not mediated by the CD28/B7 interaction. 750 22

CD40 is a membrane differentiation antigen constitutively expressed on B cells that induces B cell growth and Ig synthesis after ligation with anti-CD40 mAb or with the recently identified CD40 ligand (CD40L). CD40L is rapidly induced on T cells after activation with anti-CD3 mAb or mitogens. While CD40-CD40L interactions are clearly beneficial to B cells, we speculated that a reciprocal costimulation of T cells might also occur. We have used genetic transfection to demonstrate that interactions between human small, resting T cells and CD40+ murine transfectants substantially augmented anti-CD3 induced T cell proliferation and resulted in the generation of CTL. T cell proliferation costimulated by CD40 was IL-2 dependent. The ability of CD40+ transfectants to costimulate T cell proliferation was specific in that VCAM-1+, CD54+, CD72+, CD56+, CD31+, and fas+ transfectants in the same host cells were inactive. CD4+ T cells preferentially responded to CD40 costimulation, whereas CD8+ T cells were substantially less reactive. By contrast, costimulation with B7 transfectants induced equivalent proliferation in the CD4+ and CD8+ T cell subsets. In addition, adult naive and memory T cells, as well as cord blood T cells, were responsive to CD40. These findings suggest that the CD40-CD40L costimulation pathway may allow for selective expansion of CD4+ T cells after interaction with CD40-bearing APC. The relatively restricted expression of CD40 on APC, as well as on medullary and cortical thymic epithelium, indicates a possible role for this interaction in T cell differentiation and activation.
 ...
PMID:CD40 preferentially costimulates activation of CD4+ T lymphocytes. 750 25


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>