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)

In this study we examined the association of a promiscuous malaria T cell epitope, CS.T3, to different HLA-DR alleles. A large series of singly substituted or truncated variants of CS.T3 was prepared and tested for the ability to be recognised in association with, or to bind to, three distinct HLA-DR alleles (DR1, DRw11, and DRw14(w6)) and three natural variants of HLA-DRw11. We found that although association with the different DR molecules mapped to identical or closely overlapping regions of the peptide, distinct substitutions could drastically influence the capacity of the peptide to interact with one but not another of the three DR molecules tested. Based on analysis of the distribution of residues recognized by T cell clones restricted to the different DR alleles, we suggest that the peptide CS.T3 is not bound, at least for the three DR examined, as an alpha-helix. In addition we tested three subtypes of DRw11 as APC for the CS.T3 analogues and observed that the peptide is most likely bound in the same conformation to the three natural variants of the DRw11 molecule.
 ...
PMID:Analysis of the permissive association of a malaria T cell epitope with DR molecules. 170 96

No vaccine is yet available against serogroup B meningococci, which are a common cause of bacterial meningitis. Some outer membrane proteins (OMP), LPS, and capsular polysaccharides have been identified as protective Ag. The amino acid sequence of the protective B cell epitopes present within the class 1 OMP has been described recently. Synthetic peptides containing OMP B cell epitopes as well as capsular polysaccharides or LPS protective B cell epitopes have to be presented to the immune system in association with T cell epitopes to achieve an optimal Ir. The use of homologous, i.e., meningococcal, T cell epitopes has many advantages. We therefore investigated recognition sites for human T cells within the meningococcal class 1 OMP. We have synthesized 16 class 1 OMP-derived peptides encompassing predicted T cell epitopes. Peptides corresponding to both surface loops and trans-membrane regions (some of which occur as amphipathic beta-sheets) of the class 1 OMP were found to be recognized by T cells. In addition, 10 of 11 peptides containing predicted amphipathic alpha-helices and four of five peptides containing T cell epitope motifs according to Rothbard and Taylor (Rothbard, J. B., and W. R. Taylor. 1988. EMBO J 7:93) were recognized by lymphocytes from one or more volunteers. Some of the T and B cell epitopes were shown to map to identical regions of the protein. At least six of the peptides that were found to contain T cell epitopes show homology to constant regions of the meningococcal class 3 OMP and the gonococcal porins PIA and PIB. Peptide-specific T cell lines and T cell clones were established to investigate peptide recognition in more detail. The use of a panel of HLA-typed APC revealed clear HLA-DR restriction patterns. It seems possible now to develop a (semi-) synthetic meningococcal vaccine with a limited number of constant T cell epitopes that cover all HLA-DR locus products.
 ...
PMID:T cell recognition of Neisseria meningitidis class 1 outer membrane proteins. Identification of T cell epitopes with selected synthetic peptides and determination of HLA restriction elements. 171 91

We studied whether abnormalities in epidermal APC could be responsible for intracutaneous T cell activation in atopic dermatitis (AD). In the absence of added Ag, patients' peripheral blood T cells demonstrated significantly increased proliferation to their autologous lesional epidermal cells (mean +/- SEM = 19,726 +/- 9,754 cpm [3H]TdR uptake) relative to epidermal cells from uninvolved AD skin (2179 +/- 697 cpm) (n = 10) (p = 0.0001, log transformed data). AD T cell proliferative responses to autologous epidermal cells were dependent upon cells expressing HLA-DR, CD1a, and CD36, and not upon keratinocytes or their cytokines. Ultrastructurally, these cells ranged from typical Langerhans cells to indeterminate cells with irregular nuclear contours. Enriched populations of lesional AD Langerhans cells were highly stimulatory for autologous T cells, whereas equal numbers of Langerhans cells from non atopic epidermis were poor stimulators, even at high concentrations. The dermal perivascular dendritic cell markers CD36 and CD1b, not usually present on normal epidermal APC, were expressed by 40 and 60% of lesional AD CD1a+ epidermal Langerhans cells, respectively. Addition of anti-CD1b to cocultures of AD epidermal cells and autologous T lymphocytes augmented T cell activation, suggesting that the expression of CD1b by AD Langerhans cells may represent over expression of a molecule functionally linked to the enhanced T cell stimulatory capacity of these cells. Thus, stimulatory signals for T cells contained within AD epidermis are carried by cells in an abnormal differentiation state as indicated by expression of phenotypic characteristics of both epidermal and dermal antigen presenting cells (HLA-DR+, CD1a+, CD1b+, CD36+). We propose that activation of autologous T cells by an altered cutaneous APC population may represent a mechanism for the hyperactive and disordered cell-mediated immune response that characterizes the dermatitic lesions of AD.
 ...
PMID:Hyperstimulatory CD1a+CD1b+CD36+ Langerhans cells are responsible for increased autologous T lymphocyte reactivity to lesional epidermal cells of patients with atopic dermatitis. 171 88

The cellular distribution of two anti-HLA-DR-like monoclonal antibodies was examined. The reagents showed typical affinity to E- cells, adherent cells and activated T cells. Functionally, they affected the presentation of PPD antigen from APC to T cells in autologous and allogeneic mixed lymphocyte reaction. One of them significantly influenced the proliferation of T helper cells activated polyclonally with PHA.
 ...
PMID:Examination of two anti-HLA-DR-like monoclonal antibodies. 242 3

We studied the polymorphisms of HLA-DR and HLA-DQ products from HLA-DRw13 haplotypes by analyzing the restriction of influenza A-specific cloned T cells from an HLA-DRw13,DQw1,Dw19 homozygous individual. The results show that some functional epitopes, which can be borne by either HLA-DR or HLA-DQ molecules, are strictly correlated with the HLA-Dw19 subtype of HLA-DRw13. This clearly indicates that both HLA-DR and HLA-DQ products contribute to the HLA-Dw19 subdivision of HLA-DRw13. At least two different restricting epitopes are borne by DR products: one is correlated with the HLA-DRw13 serologically defined specificity, which includes Dw19 and Dw18 haplotypes; the other is correlated with the only HLA-Dw19 subtype of HLA-DRw13. Restricting epitopes borne by DQ molecules have been found on Dw19 cells only. DQ-restricted clones were unable to react with DQw1 APC of any other haplotypes tested, including DR1, DR2-long, DR2-short, and DRw14, demonstrating a high degree of functional polymorphism among the serologically defined DQw1 specificities.
 ...
PMID:Highly polymorphic products of both HLA-DR and HLA-DQ genes contribute to the polymorphism of the HLA-DRw13 haplotype. 242 44

HLA-DR3- and HLA-DRw52-associated functional polymorphism was investigated with selected tetanus toxoid (TT)-specific T cell clones. We have shown earlier that HLA-DR antigens are encoded by two distinct loci, DR beta I and DR beta III. The alloantigenic determinant(s) defined by the serological HLA-DR3 specificity map to the former, while the supratypic HLA-DRw52 determinants map to DR beta III. Furthermore, we have recently recognized by DNA sequencing three alleles of HLA-DRw52 at locus DR beta III, referred to as 52 a, b, and c. Our objective was to correlate the pattern of T cell restriction with the gene products of individual DR beta chain loci and with the three newly described alleles of locus DR beta III. Among the selected T cell clones, 5 reacted exclusively when TT was presented by HLA-DR3+ APCs (TT-DR3-APC). In contrast, two T cell clones were stimulated by TT-DRw52-APC. More specifically, these two T cell clones (Clones 10 and 16) were stimulated by different subsets of TT-DRw52-APC. Clone 16 responded to some DR3 and TT-DRw6-APC, while clone 10 was stimulated by other TT-DR3 and TT-DRw6, and all TT-DR5-APC. This same pattern of DRw52 restriction was found in panel, as well as in family studies. Because this suggested a correlation with the pattern of DRw52 polymorphism observed earlier by DNA sequencing and oligonucleotide hybridization, the APC used in these experiments were typed for the 52 a, b, and c alleles of locus DR beta III by allele-specific oligonucleotide probes. This distribution overlapped exactly with the stimulation pattern defined by the T cell clones. Clone 16 responded to TT-52a-APC, clone 10 to TT-52b-APC, and both clones to a TT-52c-APC. The response of the T cell clones was inhibited differentially by mAbs to DR. Raising TT concentration, or increasing HLA-class II expression with INF-gamma both affected the magnitude of response of the TT-specific clones but did not modify their specificities. These results demonstrate that a restriction specificity can be attributed to the DR beta III locus and illustrate the functional relevance of the polymorphism observed at this locus. This is of special interest in view of the striking difference in the pattern of structural diversity among alleles of DR beta I and DR beta III.
 ...
PMID:Functional polymorphism of each of the two HLA-DR beta chain loci demonstrated with antigen-specific DR3- and DRw52-restricted T cell clones. 245 Sep 55

Three HSV type 1 (HSV-1) and HSV type 2 (HSV-2) common ("HSV-type common") and three HSV-1 specific CTL clones, which were CD3+, CD4+, CD8-, 4B4+, and 2H4-, were established. These clones proliferated in response to stimulation with HSV in the presence of autologous APC. The HSV type specificity of the proliferative response was identical with that of the cytotoxic activity of the clones. The cytotoxic activity and the proliferative response were both inhibited by addition of anti-HLA-DR mAb to the culture. After culture of these CTL clones with autologous B cells and macrophages followed by HSV Ag stimulation, anti-HSV antibody was detected in the culture supernatant. The HSV type specificity of the helper function for antibody production was identical with that of the cytotoxicity, i.e., HSV-type common clones, upon stimulation with either HSV-1, or HSV-2, and HSV-1-specific clones, upon stimulation with HSV-1 but not with HSV-2, showed helper activity for anti-HSV antibody production by autologous B cells. Moreover, it was found that these clones produced humoral factors which help autologous B cells to produce antibody. The helper factors were produced by T cell clones in an HSV-type-specific manner. These data suggest that some CD4+ T cells can simultaneously manifest both specific cytotoxicity and helper activity for Ag-specific antibody production by B cells, and that these multifunctional T cells might play an important role in protection against viral infection.
 ...
PMID:Helper activity in antigen-specific antibody production mediated by CD4+ human cytotoxic T cell clones directed against herpes simplex virus. 245 88

We have characterized five human T cell clones specific for tetanus toxin. The combination of different techniques allowed us to precisely map two T cell epitopes within fragments 830-843 and 1273-1284 of tetanus toxin, as formally demonstrated by the use of corresponding synthetic peptides. The three other T cell clones were specific for regions 2-602, 604-742, and 865-1315 of tetanus toxin, respectively. The five T cell clones were shown to be restricted to HLA-DR Ag. Furthermore, the allele of HLA-DR utilized by the various epitopes has been determined. The use of HLA-DR-transfected L cells as APC directly demonstrated that two epitopes, one of which represented by fragment 1273-1284, were recognized in association with HLA-DRw52a. For the other three T cell epitopes, the data strongly suggested they were recognized in association with HLA-DR5. Finally, a sixth T cell clone was shown to be specific for tetanus toxoid, the vaccinal preparation of tetanus toxin, and not for other tetanus toxin fragments. This indicated that immunization with tetanus toxoid probably elicits a T cell response directed only in part against native tetanus toxin.
 ...
PMID:Delineation of several DR-restricted tetanus toxin T cell epitopes. 246 5

The effect of human T cell leukemia/lymphoma virus type I (HTLV-I) infection on the function and the phenotype of a human proliferating/cytotoxic T cell clone, specific for tetanus toxin, was investigated. During the period after infection, two distinct phases were observed, based on growth properties, phenotype, and functional activity of the infected cells. Phase I HTLV-I infected cells (0 to about 150 days after infection) proliferated in an IL-2-dependent way, but without the requirement for repetitive antigenic stimulation. No differences in expression of the CD2, CD3, CD4, Tp103, and CD28 Ag between these cells and the parental cells could be demonstrated, with the exception of the expression of IL-R p55 and HLA-DR Ag, which were constitutively expressed on the phase I cells. The phase I HTLV-I-infected cells, as well as the parental 827 cells reacted with a mAb specific for an epitope on the variable part of the TCR beta-chain, indicating that the TCR was not altered after HTLV-I infection. Like the parental clone, the phase I cells proliferated in response to tetanus toxin, but the tetanus toxin-specific response of the phase I cells did not require the presence of APC. Results of experiments, in which the levels of intracellular Ca2+ were measured, indicated that HTLV-I cells can acquire the capability to process Ag and present that to themselves. Phase I HTLV-I-infected T cells had lost their cytotoxic activity which was likely to be due to an effect on the lytic machinery rather than on Ag recognition by the TCR, inasmuch as it was found that phase I HTLV-I-infected T cells did no longer contain N-alpha-benzyloxy-L-lysine thiobenzylester-serine esterase activity. Furthermore, it was found that phase I HTLV-I-infected T cells had a diminished capacity to form conjugates with target cells. From a period of about 200 days after HTLV-I infection, phase II cells emerged that proliferated strongly in the absence of IL-2 and that had lost all functional activity. These cells did not express the CD3/T cell receptor complex on their surface. Phase I as well as phase II HTLV-I-infected cells were targets for CTL raised in the autologous donor.
 ...
PMID:Human T cell leukemia/lymphoma virus type I infection of a CD4+ proliferative/cytotoxic T cell clone progresses in at least two distinct phases based on changes in function and phenotype of the infected cells. 246 94

The present studies were undertaken to characterize Ag presentation by cultured human melanoma cell lines. Cell lines established from "biologically early" lesions of malignant melanoma were able to present the soluble Ag tetanus toxoid (TT) to autologous and HLA-DR-matched allogeneic, TT-immune T cell clones. Proliferation of T cell clones in response to Ag presented by primary melanoma peaked on day 2 of culture with Ag. Ag presentation was blocked by pretreatment of TT-pulsed and fixed melanoma cells with mAb against HLA-DR, but not HLA-DQ, HLA-DP, or HLA-ABC. Ag processing and presentation were inhibited by treating the melanoma cells with ammonium chloride. In parallel with previous findings from this laboratory demonstrating the inability of cell lines cultured from "advanced" primary or metastatic melanoma to induce autologous T cell proliferation, such cell lines also failed to present this exogenous Ag despite the presence of cell-surface HLA-class II molecules. Thus, in contrast to the finding in biologically early melanoma, none of the multiple TT-immune, T cell clones from autologous patients or HLA-DR matched donors was able to respond to TT presented by melanoma cells cultured from advanced disease. Co-incubation studies revealed that metastatic melanoma cells did not secrete inhibitory substances during the APC assay, however, they were able to process TT, rendering it "immunogenic" in the presence of fixed, autologous non-T cells. When fixed, autologous melanoma cells were assayed for their ability to present processed Ag; fixed cells of early but not advanced disease were able to present Ag in this setting, indicating that the presenting limb becomes flawed in the evolution of the metastatic phenotype. Finally, studies of chloroquine inhibition of the capacity of melanoma cells derived from early primary disease to stimulate autologous peripheral blood T cells suggest that such cells process and present tumor-associated Ag in the same fashion as the "model" Ag TT.
 ...
PMID:Defective antigen presentation by human melanoma cell lines cultured from advanced, but not biologically early, disease. 246 32


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