ABSTRACT
C1qR(P) is a type I cell surface glycoprotein that has been shown to enhance ingestion of suboptimally opsonized targets by phagocytes in vitro. In this study, we developed and characterized polyclonal antibodies to study the tissue distribution of this receptor targeted to either the N- or C-terminal portion of the molecule. C1qR(P) was detected in vascular endothelial cells and in a subset of pyramidal neurons in the brain, as well as neutrophils, but it was absent in most tissue macrophages. Analysis of in vitro differentiation of blood monocytes to dendritic cells demonstrated a down-regulation of the receptor as monocytes differentiate to dendritic cells, providing a possible explanation for the lack of reactivity of these cells in tissue. The predominant presence of C1qR(P) in endothelial cells, while compatible with a phagocytic role in host defense and/or clearance of cellular material, suggests other possible novel roles for this receptor.
Subject(s)
Endothelium, Vascular/chemistry , Hyaluronan Receptors , Membrane Glycoproteins , Receptors, Complement/analysis , Animals , CHO Cells , Capillaries/cytology , Carrier Proteins , Cell Differentiation , Cricetinae , Cricetulus , Dendritic Cells/chemistry , Dendritic Cells/drug effects , Endothelium, Vascular/cytology , Gene Expression Regulation , Humans , Immunoenzyme Techniques , Macrophages/chemistry , Macrophages, Peritoneal/chemistry , Mice , Microglia/chemistry , Mitochondrial Proteins , Monocytes/chemistry , Monocytes/cytology , Myocardium/chemistry , Neoplasm Proteins/analysis , Nerve Tissue Proteins/analysis , Neutrophils/chemistry , Nucleopolyhedroviruses/genetics , Organ Specificity , Phagocytosis , Pyramidal Cells/chemistry , Rats , Receptors, Complement/genetics , Receptors, Complement/immunology , Receptors, Complement/physiology , Recombinant Fusion Proteins/analysis , Spodoptera/cytology , Transfection , Tumor Necrosis Factor-alpha/pharmacology , U937 Cells/chemistry , Umbilical Veins/cytology , Viscera/chemistryABSTRACT
Human C1qR(P) is a highly glycosylated transmembrane protein that is the human C1q receptor/receptor component that in vitro mediates enhancement of Fc- and C3b-mediated phagocytosis. A human genomic clone and a murine genomic clone that is 73% identical in sequence with the coding region for human C1qR(P) cDNA have been isolated. Chromosomal localization of the human and murine gene demonstrates that these genes are syntenic. Murine cell lines of diverse myeloid origins are shown to respond to interaction of C1q with the enhancement of phagocytosis similar to that seen previously in human peripheral blood monocytes. Northern blot, RT-PCR, Western blot and FACS analyses demonstrated that mC1qR(P) is expressed in these murine myeloid cell lines, but not in a mouse epithelial cell line, similar to the cell type expression of the human gene product. A polyclonal antibody to a peptide sequence common to the deduced sequence from the both murine and human C1qR(P) inhibited the enhancement of phagocytosis response to C1q when cells were permeabilized to permit access of the antibody to the intracellular milieu. These data support the postulate that the identified murine and human genes are homologs, confirm the previously predicted intracellular location of the C-terminus of the molecule, and indicates the necessary role of this intracellular domain in transducing the signal that leads to enhancement of phagocytic function.
Subject(s)
Complement C1q/immunology , Hyaluronan Receptors , Membrane Glycoproteins/genetics , Phagocytosis/immunology , Receptors, Complement/genetics , Amino Acid Sequence , Animals , Base Sequence , Carrier Proteins , Cell Line , Chromosome Mapping , DNA, Complementary , Flow Cytometry/methods , Gene Expression Profiling , Humans , Membrane Glycoproteins/immunology , Mice , Microscopy, Fluorescence/methods , Mitochondrial Proteins , Molecular Sequence Data , RNA, Messenger , Rabbits , Receptors, Complement/immunology , Sheep , U937 CellsABSTRACT
OBJECTIVE: To investigate the suitability of HIV sequence analysis, based on the p17 region of the gag gene, to characterize the sexual networks in and around a trading town in south-west Uganda. METHODS: Blood samples were obtained from 54 HIV-seropositive members of three distinct sexual networks and phylogenetic analysis carried out on proviral DNA sequences obtained from the p17 region of gag from 53 individuals. RESULTS: Despite documented evidence of very little sexual mixing between residents of the trading town, fishing village and surrounding rural area, there was no evidence of clustering of sequences associated with place of residence. More strikingly, known sexual partners failed to show significantly related sequences, and the two pairs of sequences that did show significant similarity came from individuals who had no known social or sexual contact. CONCLUSIONS: Sequence analyses such as those described here have proved effective in confirming or identifying epidemiological links not only following single transmission events but also within risk groups. However, the results from Uganda contrast markedly with those from Europe and the United States. The length of time that the community has been infected, the number of occasions when the virus has been introduced and the high degree of partner change may contribute to the lack of supportive evidence for sociological studies of sexual networks in Uganda.