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Query: UMLS:C0033036 (APC)
 10,214 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An initial event in T cell activation is the specific adherence of T cells via their T cell receptor to the MHC peptide complex. We have studied this adherence by incubating T cells with preformed HLA DR4Dw4 peptide complexes attached to a solid support. Adherence of sodium 51Cr-labeled T cell clones specific for the influenza hemagglutinin peptide, HA 307-319, was maximal after 15 min and was specific for the HLA DR4Dw4-HA 307-319 complex. The binding was temperature dependent and could be blocked with azide or protein kinase C inhibitors, indicating that for adherence the T cells need to be metabolically active and have a functioning protein kinase C pathway. The adherence could be blocked with CD4- or CD3-reactive murine mAb, suggesting that the TCR and CD4 molecules work in concert to induce strong adherence to the HLA DR4Dw4-HA 307-319 complex. A subsequent event in T cell activation is proliferation, which is thought to need additional proteins such as IL-1 or other adhesion molecules. MHC peptide complexes coated on microtiter plates also induced proliferation in the human T cell clones. Removal of any monocytes by treatment of human T cell clones with anti-CD14 in conjunction with C, followed by purification over a nylon wool column, did not abrogate proliferation. After prolonged culture of the T cell clones in plates coated with peptide-pulsed HLA DR4Dw4 in the presence of IL-2, the T cell clones continued to proliferate in response to peptide. These results suggest that human T cell clones do not require a second signal from a monocyte or other APC to proliferate.
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PMID:Purified HLA class II peptide complexes can induce adherence and activation of peptide-specific human T cell clones. 153 49

Dendritic cells (DC) are the major APC capable of stimulating resting T cells in human peripheral blood (PB). Recent evidence suggested that various subsets of DC and monocytes might circulate in human PB, but their exact phenotype and function had not been delineated. We have previously characterized a population of human PB DC precursors that express the myeloid marker CD33, but not the monocyte marker CD14. To identify and characterize further functional myeloid APC subsets, triple color FACS analysis and sorting was used. A CD33dimCD14dimCD16+ monocyte subset, with similar APC function but less efficient accessory function than CD14bright monocytes, was isolated. In addition to the CD33+CD14dimCD16- DC precursors, a smaller population (0.1 to 0.2% of PBMC) of CD33brightCD14dimCD16- cells with potent APC function was identified. This DC population expressed greater amounts of MHC class II, adhesion, and accessory molecules, and demonstrated a greater costimulatory capacity when freshly isolated than CD33dimCD14dim DC precursors, and therefore had the characteristics of mature, possibly tissue-derived DC. When freshly isolated, however, these DC did not express B7, and up-regulation of accessory function occurred after in vitro differentiation. These data demonstrate multiple circulating myeloid accessory and APC subsets in human PB. Phenotypic and functional differences suggest that they are at different stages of differentiation, and have specialized roles in Ag presentation in vivo. Furthermore, full functional DC differentiation, associated with B7 expression and the capacity to activate T cells maximally, is likely to occur only in specific physiologic circumstances.
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PMID:Human peripheral blood dendritic cell subsets. Isolation and characterization of precursor and mature antigen-presenting cells. 752 13

Dendritic cells (DC) are potent APC that can be purified from cultured peripheral blood non-T cells. Because no specific cell surface marker has been found, the lineage of DC remains obscure. The purpose of these studies was to determine the circulating blood cells that could give rise to functional human DC. DC were enriched when purified by standard techniques from non-T cells that were treated with L-leucyl-L-leucine methyl ester, known to be toxic to monocytes and cytolytic cells. To determine whether monocytes or B cells could give rise to DC, fresh non-T cells were sorted into CD14+ monocytes, CD19+ B cells, and CD14- and CD19- cells. Although there was some enrichment for APC function by cultured nonadherent CD14- or CD19- cells, a marked enrichment for cells with dendritic morphology and potent APC function was found in the population that was sorted by the absence of expression of CD14, CD19, CD3, and CD16. More than 90% of the CD14-CD19-CD16-CD3- sorted cells, and of control DC, expressed the myeloid markers CD13 and CD33. Therefore, fresh non-T cells were sorted based on the expression of these myeloid markers. In comparison with CD33-CD14- B cells, some of the CD33+ cells expressed CD14 dimly. However, they were easily distinguished from monocytes, which intensely expressed CD14. CD33+CD14dim cells developed dendritic processes and were more potent APC than control DC, CD33+CD14+, or CD33-CD14- cells. Although freshly isolated CD33+CD14dim DC expressed a number of cell surface molecules also expressed by CD14+ monocytes, they demonstrated lower levels of lysosomal enzymes and a lack of FcR-mediated phagocytosis in comparison with monocytes. Differentiation of morphology and phenotype of CD33+CD14dim cells occurred within 6 to 36 h in culture. However, the CD33+CD14dim cells could effectively function as APC without prolonged preincubation to develop dendritic morphology. These data indicate that human blood DC arise from precursors that express the myeloid lineage markers CD13 and CD33, but are functionally distinct from classic CD14+ monocytes.
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PMID:Isolation and characterization of human peripheral blood dendritic cells. 767 23

The relative ability of unmanipulated monocytes, B cells, and dendritic cells (DC) from peripheral blood to stimulate an allogeneic MLR has not been clearly established. We studied the allostimulatory ability of these cell types from minimally manipulated PBMC populations to exclude the induction of stimulatory properties by the complex isolation procedures commonly used to isolate blood DC. Highly purified cell populations were obtained from volunteer donors by immunolabeling PBMC with mAb directed against known lineage-associated markers and separating the positive and negative population on a FACS. These cells were used as stimulators in an allogeneic MLR. The major allostimulatory activity resides in the CD14, CD11b, and CD19 negative fractions. A mixture of antibodies to T, B, NK, monocyte, and FcRIII positive cells was then used to isolate a minor cell population that contained a markedly superstimulatory population of (CD3, CD14, CD16, CD19, and CD57) negative cells. We demonstrate that this activity is constitutive, and is not an artifact of the adherence and in vitro culture steps used in conventional DC purification procedures. We also show by rigorous depletion of the T cell responders that endogenous HLA class II positive cells in the responder population have little role in presenting processed allogeneic antigens during the primary MLR. Monocytes and B cells are stimulators of the allogeneic MLR, but are considerably less potent on a cell for cell basis than the putative DC population. Finally, because human blood and tonsil DC lack detectable CD43 by immunoperoxidase staining, in contrast to monocytes and activated B cells, we examined the ability of CD43 negative and positive cells to stimulate an allogeneic MLR. Similar allostimulatory activity for the human MLR was shown to reside in both the CD43 positive and negative fractions, suggesting that there may be some heterogeneity in the APC population.
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PMID:Allostimulatory cells in fresh human blood: heterogeneity in antigen-presenting cell populations. 769 38

We found that human monocytes differentiate into macrophages (Mp) by GM-CSF and M-CSF. The Mp induced by GM-CSF and M-CSF are different in their morphology, cell surface antigen expression and functions. In the course of that study, we found that IL-4 modulate the differentiation of monocytes induced by GM-CSF and M-CSF. IL-4 alone did not induce the proliferation and differentiation of monocytes. IL-4, however, inhibited the proliferative response of monocytes to GM-CSF. When monocytes were incubated with GM-CSF and IL-4 simultaneously, the cells recovered were non-adherent, non-phagocytic, and did not form rosette with EA. The cells were also negative in nonspecific esterase and showed an appearance of dendritic cells (DC). The DC-like cells expressed CD1, DR, DQ and CD11c, but not CD14, CD71 and 710F. The cells showed strong APC activity in alogeneic and autologous mixed lymphocyte reaction (MLR). When monocytes were incubated with M-CSF and IL-4, TRAP positive multinucleated giant cells appeared. Taken together, these results suggest that IL-4 is a principal factor that control the differential development of human monocytes into DC and multinucleated giant cells.
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PMID:[Differentiation and function of human monocytes]. 787 93

Dendritic cells (DC) have been isolated from blood, lymphoid tissue, and other tissues, as potential members of a hemopoietic lineage of specialist APC for naive T lymphocyte activation. To define human bone marrow (BM) DC we have attempted to identify allostimulatory cells with DC-like characteristics among human BM mononuclear cells (BMMC) by FACS cell sorting and immunophenotyping, monitoring the APC function of different cell lineages in the human primary MLR. We show that fresh human BM stimulates allogeneic T lymphocytes with an activity equal to or greater than that of peripheral blood. As with DC from other tissue sources, the most potent stimulatory activity was found in the low density BMMC, and these cells, like peripheral blood, stimulated a maximal allogeneic MLR response at days 5 to 6. FACS purification of the allostimulatory population in fresh human BMMC was undertaken by using a wide range of mAb directed against lineage-associated molecules of mature and immature lymphoid, erythroid, and myeloid cells. The most potent constitutive BMMC stimulatory activity was located in the CD3-, CD11b-, CD14-, CD15-, CD16-, CD19-, CD57-, and glycophorin A- population. A mixture of antibodies to these Ag was used to isolate a "mix-negative" BMMC population, which contained the most highly potent MLR-stimulatory cells. Further cytologic and immunophenotypic analysis of this population revealed an enriched population of HLA-DP+, HLA-DQ+, HLA-DR+, and CD45+ cells, with morphologic similarities to the human tonsil and blood DC. These cells were CD4- and CD1a- and were weakly CD33+ (but CD15-), suggesting a possible early myeloid origin distinct from both the committed granulocytic and monocytic lineages. In addition, they lacked both CD10 and CD20, making a lymphoid origin unlikely. Further identification of these putative DC precursors will allow analysis of the early phases of DC hemopoiesis, whereas the characterization of the MLR-stimulatory cells in human BM will be of major importance in the understanding of BM transplant failure and graft-vs-host disease.
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PMID:Identification of potent mixed leukocyte reaction-stimulatory cells in human bone marrow. Putative differentiation stage of human blood dendritic cells. 845 72

Microglial cells are resident cells of the CNS and are implicated as regulators and effectors of immune responses which occur within this compartment. The precise role of parenchymal microglia remains speculative because distinctions between these cells, perivascular "microglia," and blood-derived monocytes/macrophages are not well defined. The current study describes the phenotype and function of microglia immediately upon isolation from the non-inflamed adult human CNS and the phenotypic changes which occur in these cells when maintained in tissue culture. We find that the characteristic phenotype of immediately ex vivo parenchymal microglia (CD11c+/CD45low/CD14) corresponds to that found in situ in the "normal" human brain. The phenotype differs from that of perivascular "microglia" in situ and PBDM (both CD45hi/CD14++). The immediately ex vivo microglia express B7-2 and HLA class II molecules and can support alloantigen-induced proliferation by CD4+ T cells freshly isolated from peripheral blood. Following in vitro culture, the cells are characterized by a bipolar morphology, continued lower levels of CD45 expression compared to PBDM, and slight upregulation of B7-1 and HLA-DR antigen expression. CD14 becomes expressed at high levels on the cells, suggesting that CD14 can serve as an apparent marker of microglia activation which is not based on changes in morphology or APC capacity. Further, treatment of the cells with IFN-gamma and LPS causes further upregulation of HLA-DR and clear expression of B7-1 molecules on the surface. The capacity to characterize phenotypic and functional properties of microglia before and after activation provides an opportunity to determine means to manipulate the immune regulatory and effector properties of this cell type.
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PMID:Comparison of phenotypic and functional properties of immediately ex vivo and cultured human adult microglia. 889 87

Human peripheral blood contains a small subpopulation of immature dendritic cells (iDC) distinguished from circulating monocytes by their low expression of CD14. We utilized leukapheresis and countercurrent centrifugal elutriation to obtain myeloid origin mononuclear cell (MOMC) fractions of monocytes and iDC for study. These subpopulations were ultrastructurally and immunophenotypically similar before culture. After a 20- to 96-h culture either alone, with recombinant human granulocyte-monocyte CSF, or with endotoxin, greater up-regulation of costimulatory molecule expression was observed among iDC than among monocytes, and only iDC expressed the activation molecule CD83. Treatment with rhIL-4 caused many MOMC to develop morphologic properties of dendritic cells within 96 h, but costimulatory molecule up-regulation and CD14 down-regulation were heterogeneous, and CD83 expression was infrequent. In contrast, calcium ionophore (CI) treatment induced rapid and consistent effects in MOMC from both healthy volunteers and cancer patients, including down-regulated CD14 expression, acquisition of dendritic cell morphologic properties, up-regulated MHC and costimulatory molecule expression, and de novo CD83 expression. Many such effects occurred within 20 h of treatment. CI treatment activated purified CD14+ monocytes and also enhanced the spontaneous activation of purified CD14-/dim iDC in culture. Unfractionated MOMC, purified monocytes, and purified iDC displayed equivalently enhanced T cell-sensitizing efficiency following CI treatment. CD4+ T cell sensitization to keyhole limpet hemocyanin and CD8+ T cell sensitization to MART-1 melanoma-associated peptide were achieved in a single culture stimulation. Therefore, circulating monocytes and iDC can be induced by CI to manifest properties of activated DC, providing large numbers of efficient, nontransformed autologous APC for T cell sensitization strategies.
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PMID:Calcium ionophore-treated peripheral blood monocytes and dendritic cells rapidly display characteristics of activated dendritic cells. 937 70

Because dendritic cells (DC) play a major role in the initiation of T cell-mediated immunity, we studied the effects of glucocorticoids, well-known inhibitors of the immune and inflammatory response, on the differentiation and maturation of human DC. DC were differentiated from human monocytes by culture with GM-CSF and IL-4 for 7 days with and without dexamethasone (Dex). Cells treated with Dex (10-8 M) (Dex-DC) developed a characteristic dendritic morphology; however, membrane phenotype analysis demonstrated that they were not fully differentiated. Dex-DC expressed low levels of CD1a and, unlike untreated cells, high levels of CD14 and CD16. Molecules involved in Ag presentation (CD40, CD86, CD54) were also impaired. In contrast, molecules involved in Ag uptake (mannose receptor, CD32) and cell adhesion (CD11/CD18, CD54) were up-regulated. After exposure to TNF-alpha or CD40 ligand, Dex-DC expressed lower levels of CD83 and CD86 than untreated cells. Dex-DC showed a higher endocytic activity, a lower APC function, and a lower capacity to secrete cytokines than untreated cells. Overall, these results indicate that DC differentiated in the presence of Dex are at a more immature stage. Moreover, Dex also partially blocked terminal maturation of already differentiated DC. In conclusion, our data suggest that glucocorticoids may act at the very first step of the immune response by modulating DC differentiation, maturation, and function.
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PMID:Glucocorticoids affect human dendritic cell differentiation and maturation. 1035 62

Dendritic cells (DC) can be generated in vitro from monocytes (M-DC) or from CD34+ hemopoietic progenitor cells (CD34-DC) but their precursors are not equivalent cells, prompting a comparison of the functional capacities of these APC. Both types of DCs established from the same individuals using the same cytokines displayed a comparable phenotype of mature DC (CD1a+, CD83+, CD86+, CD4+, HLA-DR++, CD14-, CD15- ) and were equally potent stimulators of allogeneic T cell proliferation, being both more powerful than immature M-DCs. An autologous panel of APCs produced in HLA-A2+ individuals, including CD34-DC, M-DC, monocytes, and EBV-lymphoid cell line was comparatively evaluated for presentation of the Erb-B2 peptide E75 to a CTL line. After short exposures (5 h) to E75-loaded APCs, similar levels of intracellular IFN-gamma were induced in Ag-specific CD8+ T cells regardless of APC type. In sustained cultures (4-14 days), more Ag-specific T cells were obtained when peptide was presented on CD34-DC (p < 0.05) rather than on M-DC, EBV-lymphoid cell lines, or monocytes, and these effects were dose-dependent. Activated T cells expressed 4-1BB, and the presence of 4-1BB-Ig fusion protein partially blocked Ag-specific CD8+ cell activation after CD34-DC or M-DC presentation. Our results show that 34-DC have a preferential capacity to activate CD8+ T cells and that this property is not strictly correlated to their ability to induce allogeneic T cell proliferation but due to mechanisms that remain to be defined.
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PMID:Dendritic cells generated either from CD34+ progenitor cells or from monocytes differ in their ability to activate antigen-specific CD8+ T cells. 1049 Sep 52


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