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Binding of Mycobacterium tuberculosis to complement receptor type 3 expressed in mammalian cells : dependence on serum opsonins
Nonopsonic invasion of mononuclear phagocytes by Mycobacterium tuberculosis (M. tb.) is likely important in the establishment of a primary infection in the lung. M. tb. binds to a variety of phagocyte receptors, of which the mannose receptor and the complement receptor type 3 (CR3) may support nonop...
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| Format: | Thesis |
| Language: | English |
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Division of Medical Biochemistry and Structural Biology
2017
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| _version_ | 1867614255655682048 |
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| access_status_str | Open Access |
| author | Cywes, Colette |
| author2 | Ehlers, Mario R W |
| author_browse | Cywes, Colette Ehlers, Mario R W |
| author_facet | Ehlers, Mario R W Cywes, Colette |
| author_sort | Cywes, Colette |
| collection | Thesis |
| description | Nonopsonic invasion of mononuclear phagocytes by Mycobacterium tuberculosis (M. tb.) is likely important in the establishment of a primary infection in the lung. M. tb. binds to a variety of phagocyte receptors, of which the mannose receptor and the complement receptor type 3 (CR3) may support nonopsonic binding. CR3, a β₂ integrin, is a target for diverse intracellular pathogens, but its role in nonopsonic binding remains uncertain. We have examined the binding of M. tb. to human CR3 heterologously expressed in Chinese hamster ovary (CHO) cells, thereby circumventing the problems of competing receptors and endogenously synthesised complement, which are inherent in studies with mononuclear phagocytes. The surface expression and functional activity of CR3 were confirmed by rosetting with beads coupled to anti-CR3 monoclonal antibodies (MAbs) and with C3bi-coated microspheres, respectively. We found thatM. tb. binds 4-7-fold more avidly to CR3- expressing CHO cells than to wild-type cells, and importantly, that this binding is very similar in the presence of fresh or heat-inactivated human or bovine sera, or no serum. The binding of M. tb. to the transfected CHO cells is CR3-specific, as it is inhibited by anti-CDllb and anti-CD18 MAbs; interestingly, binding is not inhibited by a MAb (2LPM19c) specific for the C3bi-binding site on CDI lb. Electron micrographs of infected CR3-expressing CHO cells reveal the presence of intracellular bacteria enclosed in well-defined, membrane-bound vacuoles. We conclude that the binding of M. tb. to CR3 is nonopsonic and that the organism likely expresses a ligand that directly binds to CR3. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/25682 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:49:08.573Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2017 |
| publishDateRange | 2017 |
| publishDateSort | 2017 |
| publisher | Division of Medical Biochemistry and Structural Biology |
| publisherStr | Division of Medical Biochemistry and Structural Biology |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/25682 Binding of Mycobacterium tuberculosis to complement receptor type 3 expressed in mammalian cells : dependence on serum opsonins Cywes, Colette Ehlers, Mario R W Mycobacterium Tuberculosis - chemistry Opsonins Receptors, Complement Nonopsonic invasion of mononuclear phagocytes by Mycobacterium tuberculosis (M. tb.) is likely important in the establishment of a primary infection in the lung. M. tb. binds to a variety of phagocyte receptors, of which the mannose receptor and the complement receptor type 3 (CR3) may support nonopsonic binding. CR3, a β₂ integrin, is a target for diverse intracellular pathogens, but its role in nonopsonic binding remains uncertain. We have examined the binding of M. tb. to human CR3 heterologously expressed in Chinese hamster ovary (CHO) cells, thereby circumventing the problems of competing receptors and endogenously synthesised complement, which are inherent in studies with mononuclear phagocytes. The surface expression and functional activity of CR3 were confirmed by rosetting with beads coupled to anti-CR3 monoclonal antibodies (MAbs) and with C3bi-coated microspheres, respectively. We found thatM. tb. binds 4-7-fold more avidly to CR3- expressing CHO cells than to wild-type cells, and importantly, that this binding is very similar in the presence of fresh or heat-inactivated human or bovine sera, or no serum. The binding of M. tb. to the transfected CHO cells is CR3-specific, as it is inhibited by anti-CDllb and anti-CD18 MAbs; interestingly, binding is not inhibited by a MAb (2LPM19c) specific for the C3bi-binding site on CDI lb. Electron micrographs of infected CR3-expressing CHO cells reveal the presence of intracellular bacteria enclosed in well-defined, membrane-bound vacuoles. We conclude that the binding of M. tb. to CR3 is nonopsonic and that the organism likely expresses a ligand that directly binds to CR3. 2017-10-16T10:26:10Z 2017-10-16T10:26:10Z 1996 2017-07-20T12:31:10Z Doctoral Thesis Doctoral PhD http://hdl.handle.net/11427/25682 eng application/pdf Division of Medical Biochemistry and Structural Biology Faculty of Health Sciences University of Cape Town |
| spellingShingle | Mycobacterium Tuberculosis - chemistry Opsonins Receptors, Complement Cywes, Colette Binding of Mycobacterium tuberculosis to complement receptor type 3 expressed in mammalian cells : dependence on serum opsonins |
| thesis_degree_str | Doctoral |
| title | Binding of Mycobacterium tuberculosis to complement receptor type 3 expressed in mammalian cells : dependence on serum opsonins |
| title_full | Binding of Mycobacterium tuberculosis to complement receptor type 3 expressed in mammalian cells : dependence on serum opsonins |
| title_fullStr | Binding of Mycobacterium tuberculosis to complement receptor type 3 expressed in mammalian cells : dependence on serum opsonins |
| title_full_unstemmed | Binding of Mycobacterium tuberculosis to complement receptor type 3 expressed in mammalian cells : dependence on serum opsonins |
| title_short | Binding of Mycobacterium tuberculosis to complement receptor type 3 expressed in mammalian cells : dependence on serum opsonins |
| title_sort | binding of mycobacterium tuberculosis to complement receptor type 3 expressed in mammalian cells dependence on serum opsonins |
| topic | Mycobacterium Tuberculosis - chemistry Opsonins Receptors, Complement |
| url | http://hdl.handle.net/11427/25682 |
| work_keys_str_mv | AT cywescolette bindingofmycobacteriumtuberculosistocomplementreceptortype3expressedinmammaliancellsdependenceonserumopsonins |