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Query: UMLS:C0155339 (Brown)
 12,436 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The ability of a hyperimmune Lew anti-BN serum (HIS) to induce enhancement of (Lew/BN)F1 kidneys transplanted into Lew recipients was compared to that of the same antiserum that had been depleted of hemagglutinating anti-Ag-B antibodies by absorption with Brown-Norway (BN) RBC-absorbed sera (RAS) or platelet-absorbed sera (PAS). The RAS and PAS were as effective as the unabsorbed HIS in abrogating early rejection as assessed by renal function and promotion of long-term survival. The absorbed sera retained the capacity to block the mixed lymphocyte culture (MLC) between Lew and BN lymphocytes and to a lesser degree the MLC between Lew and BUF, WF, AUG, and ACI lymphocytes; however, strain specificity was clearly evident at high antiserum dilutions. Similarly, these absorbed sera retained the capacity to block the Fc receptor of BN lymphocytes, and this effect was completely strain specific. In contrast, hemagglutinating and cytotoxic antibodies eluted from platelets used for antiserum absorption did not react with Fc receptors as assessed by rabbit antisheep (IgG)-coated SRBC (EA) rosette formation. F(Ab')2 fragments of PAS also blocked EA rosettes. On the other hand, complement rosettes (EAC) were not inhibited by the HIS. The antibodies were therefore directed against the Fc receptor itself or a structure spatially or functionally closely related to it. Both the Fc receptors and the enhancing capacity of the antisera were strictly specific for the BN genotype. It is suggested that the anti-"Fc receptor" antibody could play an important role in the induction of enhancement by impairing host T-B collaboration as a result of its binding to graft allogeneic "Fc receptors" which appear to be analogous to the major histocompatibility complex (MHC)-coded Ia antigens of the mouse.
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PMID:The role of nonclassical Fc receptor-associated, Ag-B antigens (Ia) in rat allograft enhancement. 12 99

Phagocytosis has traditionally been viewed as a specialized function of myeloid and monocytic cells. The mannose receptor (MR) is an opsonin-independent phagocytic receptor expressed on tissue macrophages. When human MR cDNA is transfected into Cos cells, these usually non-phagocytic cells express cell surface MR and bind and ingest MR ligands such as zymosan, yeast, and Pneumocystis carinii. Expression of cDNA for Fc gamma RI (CD64), the high-affinity Fc receptor, in Cos cells confers binding but barely detectable phagocytosis of antibody-opsonized erythrocytes (EA). We report here that chimeric receptors containing the ligand-binding ectodomain of the Fc receptor and the transmembrane and cytoplasmic domains of the MR ingest bound EA very efficiently, whereas chimeras with the Fc receptor ecto- and transmembrane domains and the MR tail, or the Fc receptor ecto- and cytoplasmic domains and the MR transmembrane region, are significantly less phagocytic. All of the chimeric receptors bind ligand with equal avidity, but gain of functional phagocytosis is only conferred by the MR transmembrane and cytoplasmic domains. Endocytosis of monomeric immunoglobulin G by chimeric receptors demonstrates a similar pattern, with optimal uptake by the chimera containing both tail and transmembrane regions from the MR. The chimeric receptors with only the transmembrane or the cytoplasmic domain contributed by the MR were less efficient. Site-directed mutagenesis of the single tyrosine residue in the cytoplasmic tail (which is present in a motif homologous to an endocytosis consensus motif in the LDL receptor cytoplasmic tail [Chen, W.-J., J. L. Goldstein, and M. S. Brown. 1990. J. Biol. Chem. 265:3116]) reduces the efficiency of phagocytosis and endocytosis to a similar extent.
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PMID:Phagocytic chimeric receptors require both transmembrane and cytoplasmic domains from the mannose receptor. 146 Apr 25

The signal transduction mechanisms involved in the regulation of phagocytosis are largely unknown. We have recently shown that in neutrophils, when IgG-mediated phagocytosis is stimulated by formyl-methionyl-leucyl-phenyl-alanine (fMLP), the enhanced ingestion is dependent on the increase in [Ca2+]i which results from ligation of Fc receptors by the IgG-coated target (Rosales, C., and Brown, E. (1991) J. Immunol. 146, 3937-3944). Now, we have studied the mechanism by which this rise in [Ca2+]i occurs. Aggregated IgG, the monoclonal antibody 3G8 (which recognizes Fc receptor type III), and insoluble immune complexes caused an increase in [Ca2+]i. The rise in [Ca2+]i induced by Fc receptor ligation was resistant to pertussis toxin. In contrast, fMLP induced a rise in [Ca2+]i which was inhibited by pertussis toxin. fMLP-induced [Ca2+]i was accompanied by an accumulation of inositol 1,4,5-trisphosphate (IP3) which peaked by 15 s, and which was also abolished by pertussis toxin. IP3 accumulation after aggregated IgG, 3G8, or insoluble immune complexes was much less than after fMLP. Unlike [Ca2+]i rise induced by Fc receptor ligation, this small increase in IP3 was inhibited by pertussis toxin. These data demonstrated that the [Ca2+]i increase induced by Fc receptor ligation is not mediated by IP3. Immediate pretreatment of human polymorphonuclear neutrophils with optimal doses of fMLP also reduced subsequent increase in [Ca2+]i rise from thapsigargin, a sesquiterpene lactone tumor promoter that releases intracellular Ca2+ from IP3-sensitive stores without IP3 turnover. Similarly, to its effects on thapsigargin, fMLP inhibited the [Ca2+]i rise upon subsequent immune complex binding. Pretreatment of cells with immune complexes also prevented subsequent [Ca2+]i rise from thapsigargin and fMLP. These data demonstrate that IgG Fc receptor ligation and fMLP activation of human polymorphonuclear neutrophils use distinct signal transduction mechanisms to release Ca2+ from the same thapsigargin-sensitive intracellular pool. In contrast to fMLP, signal transduction for increased [Ca2+]i after Fc receptor stimulation does not involve a pertussis toxin-sensitive G protein, and is independent of IP3.
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PMID:Signal transduction by neutrophil immunoglobulin G Fc receptors. Dissociation of intracytoplasmic calcium concentration rise from inositol 1,4,5-trisphosphate. 153 82