Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Receptors, Complement 3d”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 739 records · Page 41Linked to original sources
PubMed2000

Follicular dendritic cell sarcoma presenting as a submucosal tumor of the stomach.

Follicular dendritic cell (FDC) sarcomas, especially those of extranodal origin, are extremely rare, and this entity could easily be missed without a high index of suspicion. We report a case of FDC sarcoma presenting as a submucosal tumor of the stomach in a 45-year-old man. The mass was a spindle and epithelioid mesenchymal tumor with many individually scattered and perivascular aggregates of lymphocytes. Immunohistochemical and ultrastructural studies confirmed the diagnosis. Although more than 50 cases of this tumor have been documented in the English literature, to our knowledge the presentation of FDC sarcoma as a submucosal tumor of the stomach has never been recorded. This case highlights the occurrence of FDC sarcoma as a submucosal tumor of the gastrointestinal tract. We believe that FDC sarcoma should be included in the differential diagnosis of spindle or epithelioid cell tumors of the gastrointestinal hollow viscus to prevent this still under-recognized tumor from being overlooked.

Dendritic Cells, Follicular↗
PubMed1999

Heterogeneous nuclear ribonucleoprotein D0B is a sequence-specific DNA-binding protein.

Complement receptor 2 (CR2) is important in the regulation of the B lymphocyte response; the regulation of its expression is therefore of central importance. We recently reported that a 42 kDa heterogeneous nuclear ribonucleoprotein (hnRNP) is involved in the transcriptional regulation of the human CR2 gene [Tolnay, Lambris and Tsokos (1997) J. Immunol. 159, 5492-5501]. We cloned the cDNA encoding this protein and found it to be identical with hnRNP D0B, a sequence-specific RNA-binding protein. By using a set of mutated oligonucleotides, we demonstrated that the recombinant hnRNP D0B displays sequence specificity for double-stranded oligonucleotide defined by the CR2 promoter. We conducted electrophoretic mobility-shift assays to estimate the apparent Kd of hnRNP D0B for the double-stranded DNA motif and found it to be 59 nM. Interestingly, hnRNP D0B displayed affinities of 28 and 18 nM for the sense and anti-sense strands of the CR2 promoter-defined oligonucleotide respectively. The significantly greater binding affinity of hnRNP D0B for single-stranded DNA than for double-stranded DNA suggests that the protein might melt the double helix. The intranuclear concentration of sequence-specific protein was estimated to be 250-400 nM, indicating that the protein binds to the CR2 promoter in vivo. Co-precipitation of a complex formed in vivo between hnRNP D0B and the TATA-binding protein demonstrates that hnRNP D0B interacts with the basal transcription apparatus. Our results suggest a new physiological role for hnRNP D0B that involves binding to double- and single-stranded DNA sequences in a specific manner and functioning as a transcription factor.

Base Sequence↗
PubMed1999

In vitro analysis of complement-dependent HIV-1 cell infection using a model system.

Previous studies based on the use of human serum as a source of C have provided evidence for the C-dependent enhancement of cell infection by HIV-1. The present study was undertaken to distinguish C from other serum factors and to identify the proteins and the mechanisms involved in C-dependent cell infection by HIV-1. The classical C activation pathway was reconstituted from the proteins C1q, C1r, C1s, C4, C2, C3, factor H, and factor I; each were purified to homogeneity. A mixture of these proteins at physiological concentrations was shown to reproduce the ability of normal human serum to enhance the infection of MT2 cells by HIV-1 at low doses of virus. This enhancing effect was abolished when heat-inactivated serum and C2- or C3-depleted serum were used, and was restored upon addition of the corresponding purified proteins. A mixture of two synthetic peptides corresponding to positions 10-15 and 90-97 of human C receptor type 2 (CD21) as well as soluble CD4 both inhibited the C-dependent infection process. These data provide unambiguous evidence that HIV-1 triggers a direct activation of the classical C pathway in vitro and thereby facilitates the infection of MT2 cells at low doses of virus. These findings are consistent with a mechanism involving increased interaction between the virus opsonized by C3b-derived fragment(s) and the CD21 cell receptors and subsequent virus entry through CD4 receptors.

Acquired Immunodeficiency Syndrome↗
PubMed1999

Cutting edge: recruitment of the CD19/CD21 coreceptor to B cell antigen receptor is required for antigen-mediated expression of Bcl-2 by resting and cycling hen egg lysozyme transgenic B cells.

Recruitment of the CD19/CD21 coreceptor is thought to lower the threshold for effective signaling through the B cell Ag receptor. We provide evidence supporting a second role for coreceptor recruitment, and that is to enhance the survival/proliferative potential of the responding B cells. We show that B cell Ag receptor signaling in the absence of coreceptor recruitment induces cellular accumulation of the anti-apoptotic protein Bcl-xL, whereas CD19-mediated signals are required for Bcl-2 accumulation. The expression of both anti-apoptotic proteins correlates with the enhanced responsiveness of both resting and cycling B cells to growth-promoting signals delivered through CD40. These results provide further evidence for the necessity of coreceptor recruitment during Ag-dependent B cell activation and indicate that Ags derived from inflammatory sites function as better thymus-dependent Ags than their counterparts not coated with complement fragments.

Animals↗
PubMedDate not supplied

[Role of the complement C3 protein in the control of the specific immune response].

Whereas complement system was usually considered as a member of innate defence, one of its components (C3) is now thought to facilitate acquired immunity. This role is due first to its capacity to covalently bind to antigens and secondly to the interactions of its proteolytic fragments with different receptors expressed on most cells involved in the acquired immune response. After activation in the plasma, C3 is proteolysed in fragments which possess various biological activities, as a modification in cell activities occurred after binding to cell surface receptors. Injection of low amount of antigen results in a modified immune response in C3 deficient animals with a decrease in the level of specific antibodies and an absence of IgM/IgG switch. One of the fragments of C3 (C3d) and its receptor (CR2) seem particularly important : knock out animals in C3 or CR2 have similar phenotypes. Mice with a deficit in CR2 restricted to the B lymphocytes present a strong reduction in the number and the size of germinal centers. Moreover, expression of CR2 on follicular dendritic cells is necessary for the generation of a strong memory response. C3 is also involved in the control of the intracellular processing of the antigen as the use of covalent complex (C3b-antigen) instead of free antigen increases the amount of stable MHC class II molecules at the antigen presenting cells surface. In summary, C3 fragments increase cell to cell interactions, induce intracellular signalling after binding to their receptors and increases intracellular processing of antigens. A better knowledge of the different roles of C3 may be useful to modify the immune response and to promote the immune memory, a domain where C3 seems particularly important.

Animals↗
PubMed1999

Distribution of immune cells expressing CD3a, CD21 and S-100 protein markers in the porcine gut-associated lymphoid tissues.

The distribution of immune cells within the gut-associated lymphoid tissues (GALT) of swine is highly organized. The appearance of such cells could not be separated from the effects of age, weaning and exposure to environment. Here, we have examined the distribution patterns of a subset of CD3a+ T and CD21+ B cells as well as S-100 protein+ cells and secretory (s) IgA+ cells within GALT compartments (such as jejunal lamina propria = JLP, ileal Peyerís patches = IPP, and mesenteric lymph node = MLN) of juvenile 8-week-old conventionally reared pigs using either two monoclonal antibodies (mAbs) or polyclonal antibodies (pAbs) in the immunohistochemical staining techniques with avidin-biotin complex (ABC) or peroxidase-antiperoxidase complex (PAP), respectively. The most potent porcine T-cell marker--CD3 surface antigen--is expressed as CD3a epitope on ileal intraepithelial lymphocytes, and numerous lymphocytes in the extrafollicular areas of MLN and dome region of IPP. Conversely, the cells expressing CD21 surface molecules were only demonstrable in the interfollicular areas of MLN and in the germinal centers of IPP. A strong reaction to sIgA was displayed by the plasma cells in the lumen of crypts and those residing the lamina propria of jejunum and ileum. The S-100 protein+ cells were numerous in JLP around the crypts and in IPP of weaned pigs. Both applied mAbs proved to be useful reagents for phenotypic and functional analyses of porcine lymphoid cell subsets by the ABC technique. However, further investigation of the S-100 protein marker is needed to determine which (if any) subset of porcine CD3+ CD4- CD8+ T cells could be designated as orthologue of human CD8+ CD11b+ suppressor T cells.

Animals↗
PubMed1999

Lymphoid transcription of the murine CD21 gene is positively regulated by histone acetylation.

Intronic transcriptional control sequences influence the cell- and tissue-specific expression of the CD21 gene. The interactions of such intronic control sequences, which are physically separated from the gene's promoters, suggest that factors that alter chromatin structure might be influential in this process. Accordingly, we analyzed the effect of histone acetylation on the expression of CD21 in nonexpressing T and B lymphocytes, respectively. The acetylase inhibitors sodium butyrate and trichostatin A were used to create hyperacetylated histones. The CD21 gene was specifically activated in the previously transcriptionally quiescent cells in a time- and dose-dependent fashion: the expression of a number of other genes was not influenced. These data suggest a model of cell-type-specific deacetylase activity that serves to repress gene transcription when present and active.

Acetylation↗
PubMed2000

Primary extra-nodal lymphoma of the urinary bladder.

Primary non-Hodgkin's lymphoma of the urinary bladder is rare. Only a few cases have been reported. We report the case of a woman with non-Hodgkin's lymphoma of urinary bladder and review the literature.

Antigens, CD20↗
PubMed2000

Tracing uptake of C3dg-conjugated antigen into B cells via complement receptor type 2 (CR2, CD21).

Electron microscopy was used to study the internalization and delivery of ligands for complement receptor type 2 (CR2, CD21) to endocytic compartments of B-lymphoblastoid Raji cells. Opsonized antigen was mimicked with purified C3dg conjugated to colloidal gold. C3dg-gold bound specifically to the cell surface in a time-dependent manner, and preincubation of the cells with a monoclonal antibody blocking the CR2 ligand-binding site completely inhibited any C3dg-gold binding. Notably, the binding of C3d-gold was confined to cell surface protrusions, eg, microvilli. C3dg-gold was apparently internalized through coated pits located at the bases of microvilli and could be traced to different compartments of the endocytic pathway. The morphologic characteristics and intracellular distribution of these multivesicular or multilaminar structures were compatible with those of compartments known to harbor major histocompatibility complex (MHC) class II molecules. Immunolabeling showed that the internalized C3dg-gold colocalized with MHC class II in these structures. These data provide the first ultrastructural evidence that complement-coated antigens are endocytosed by antigen-nonspecific B cells by CR2 and are delivered to the compartments in which peptide loading for antigen presentation occurs. They support the notion that CR2 may play a role in antigen presentation by B cells regardless of B-cell receptor specificity. (Blood. 2000;95:2617-2623)

Antigen Presentation↗
PubMedDate not supplied

CD21.

Explore the source record for details and available documents.

Amino Acid Sequence↗
PubMed2000

Mediastinal Castleman's disease complicated by follicular dendritic cell tumour.

We describe a rare case of follicular dendritic cell tumour which had arisen over the background of hyaline vascular type of Castleman's disease at the mediastinal location. Constellation of histology and immunohistochemistry using CD21 antibody and non-reactivity to CD15, CD30, cytokeratin and epithelial membrane antigen helped us diagnose this case. The literature is reviewed, specially with reference to the genesis of follicular dendritic cell neoplasm at the backdrop of Castleman's disease and its clinical relevance.

Adult↗
PubMed2002

Complement's participation in acquired immunity.

The preliminary evidence for the involvement of complement in promoting primary humoral responses dates back over a quarter of a century. However, it is only in the course of the past decade or so that the detailed mechanisms underlying complement's influence have been characterized in depth. It is now clear that complement serves as a regulator of several B cell functions, including specific antibody production, antigen uptake, processing and presentation, and shaping of the B cell repertoire. Of key importance, in this respect, is the role played by the B cell-signaling triad consisting of the B cell receptor for antigen (BCR), a complex composed of the iC3b/C3d fragment-binding complement type 2 receptor (CR2, CD21) and its signaling element CD19 and the IgG-binding receptor FcgammaRIIb (CD32). The positive or negative outcome of signaling through this triad is determined by the context in which antigen is seen, be it alone or in association with natural or induced antibodies and/or C3-complement fragments. The aim of this review is to describe the present status of our understanding of complement's participation in acquired immunity and the regulation of autoimmune responses.

Animals↗
PubMed2002

Infection of immortalized human epithelial cell line Hacat with high-concentration Epstein-Barr virus.

OBJECTIVE: To study the mechanism by which Epstein-Barr (EB) virus infects human epithelial cells. METHODS: Large-scale culture of marmoset lymphocytes B958 was carried out to extract and condense EB virus therein. Titrated by lymphocytes from fetal umbilical blood, the EB virus of high concentration was used to infect immortalized human epithelial cell line Hacat, followed by genomic DNA extraction from the Hacat cells and amplification of the special DNA sequence Bam HIw fragments of EBV genomic DNA by PCR. Southern blotting and in situ hybridization were employed to confirm the result of PCR. RESULTS: The results of PCR, Southern blotting and in situ hybridization all indicated that high-concentration EBV could infect Hacat cell line, but the rate of infection was rather low. CONCLUSION: There is an unknown pathway of infection for EBV entry into the epithelial cells other than the mediation by CR2 or pIgR.

Cell Line↗
PubMed2001

[Infection of mutated mouse complement receptor type II by Epstein-Barr virus].

Site-directed mutagenesis method was used to introduce two desired mutations, which were confirmed by DNA sequencing, into mouse complement receptor Type II gene(MCR2). Then the constructed eukaryotic expression vectors containing wild type mouse CR2/1(wtMCR2/1), mutant type mouse CR2/1 (mtMCR2/1) and human CR2 (hCR2) cDNA were transferred into mouse SP2/0 cells by electroporation. After two-week screening by G418, the stably transfected clones were obtained. Several ways including PCR, RT-PCR, and immunohistochemistry were utilized to screen those clones with interesting genes integrated and expressed. Then Epstein-Barr virus(EBV) was used to infect these transfected cells and EBER-1 (EBV encoded RNAs) hybridization results showed that only hCR2 and mtMCR2 transfected SP2/0 cells could be infected by EBV, but positive rate of the former was much higher than the latter. This study sets groundwork for elucidating the mechanism by which EBV enters the cells and for establishing the animal model of EBV-related nasopharyngeal carcinoma (NPC).

Animals↗
PubMed1992

The CD19/CD21 signal transducing complex of human B lymphocytes includes the target of antiproliferative antibody-1 and Leu-13 molecules.

CD19 is a member of the Ig superfamily expressed on the surface of B lymphocytes that may be involved in the regulation of B cell function. Immunoprecipitation studies with B cell lines solubilized by digitonin have shown CD19 to be part of a multimolecular complex that includes CD21 (CR2) and other unidentified proteins. In this study, two of the CD19-associated proteins were identified as TAPA-1, which is expressed on most cell types, and Leu-13, which is expressed on subsets of lymphoid cells. TAPA-1 and Leu-13 are physically associated in many cell lineages. CD19 and CD21 mAb each specifically coprecipitated proteins of the same size as those precipitated by TAPA-1 and Leu-13 mAb from B cell lines and cDNA-transfected K562 cell lines. Western blot analysis with a TAPA-1 mAb verified the identity of TAPA-1 in CD19 and CD21 immunoprecipitated materials. In addition, when TAPA-1 or Leu-13 were crosslinked and patched on the cell surface, all of the CD19 comigrated with TAPA-1 and some of the CD19 comigrated with Leu-13. Furthermore, mAb binding to CD19, CD21, TAPA-1, and Leu-13 on B cell lines induced similar biologic responses, including the induction of homotypic adhesion, inhibition of proliferation, and an augmentation of the increase in intracellular [Ca2+] induced by suboptimal cross-linking of surface Ig on B cell lines. Together, these data suggest that TAPA-1 and Leu-13 are broadly expressed members of a signal transduction complex in which lineage-specific proteins, such as CD19 and CD21, provide cell-specific functions.

Antigens, CD↗
PubMed1992

Expression, molecular association, and functions of C3 complement receptors CR1 (CD35) and CR2 (CD21) on the human T cell line HPB-ALL.

We have investigated the expression, molecular association, ligand binding properties, and ability to transduce intracellular signals of CR1 and CR2 C3 receptors on cells of the human HPB-ALL T cell line. CR1 and CR2 on HPB-ALL cells bound polymeric C3b and C3dg and several anti-CR1 and anti-CR2 mAb recognizing different epitopes of the receptors on normal peripheral blood cells. Immunoprecipitated CR1 and CR2 exhibited similar m.w. to those of the receptors on normal peripheral blood T and B lymphocytes. CR1 and CR2 were partially associated in the form of CR1/CR2 complexes in the cell membrane as assessed by the ability of the receptors to cocap and cointernalize and to form a detergent-sensitive complex upon immunoprecipitation analysis. Triggering of CR2 with mAb OKB7 that recognizes an epitope associated with the ligand binding site of the receptor induced an increase in intracellular free calcium concentration in HPB-ALL cells. The signal provided by mAb OKB7 did not synergize with that triggered by anti-CD3 mAb UCHT1. Triggering of CR1 did not result in changes in intracellular free calcium concentration. Our observations have significance for the biology of normal human T cells because the majority of peripheral blood T cells that express CR1 also expressed CR2 and because a change in (Ca2+)i was induced by mAb OKB7 in purified normal T cells. These functions may be relevant for the regulatory role of C3 fragments on the immune response to T-dependent Ag and for the penetration into T cells of lymphocytotropic viruses.

Antigens, Differentiation, B-Lymphocyte↗
PubMed1992

Complement activation in the follicular light zone of human lymphoid tissues.

A comparative immunohistochemical study of the distribution pattern of complement components and regulatory proteins within secondary lymphoid follicles was performed by the immunoperoxidase technique. Fifteen lymphoid tissues including appendices. Peyer's patches and tonsils were analysed. Sixty secondary lymphoid follicles with evident polarity, that is, the distinct coexistence of a light zone, dark zone and mantle zone in the same lymphoid follicle, were tested with single antibodies. The light zones were consistently immunostained in a dendritic meshwork pattern with all antibodies. The immunostaining patterns were classified into two major groups based on the immunoreactivity of the dark zone. One immunostaining pattern was characterized by no immunostaining of the dark zone to the majority of the antigens. The second group was characterized by a diffusely weak to moderate dendritic meshwork pattern of the dark zone to some of the immunostainings of C9 (monoclonal), S-protein, and DF-DRC1, and all immunostainings of CR1 (CD35), Ber-Mac-DRC (CD35), CR2 (CD21), and R4/23. All four complement regulatory proteins were localized by immunoelectron microscopy attached to the cell surface of the cells, including follicular dendritic cells, in the light zone. Our data indicate that there is an evident functional difference between the light zone and the dark zone, and that complete activation of the complement system occurs only in the light zone.

Antigens, Differentiation, B-Lymphocyte↗