What does polysaccharide capsule do?
Polysaccharide capsules are structures found on the cell surface of a broad range of bacterial species. The polysaccharide capsule often constitutes the outermost layer of the cell, and therefore is often involved in mediating direct interactions between the bacteria and its environment.
How does polysaccharide capsule inhibit phagocytosis?
Capsules can resist unenhanced attachment by by preventing pathogen-associated molecular patterns or from binding to endocytic pattern-recognition receptors on the surface of the phagocytes.
What are immune polysaccharides?
4.1. Polysaccharides stimulate immune cells by means of specific receptors, for example in necrophagous and macrophage cells by means of bonds between functional groups of polysaccharides and molecular groups on the cell surface.
How do polysaccharide vaccines work?
Polysaccharide vaccines stimulate B-cell responses, thereby resulting in type-specific antibody production that enhances ingestion and killing of the pathogens by phagocytes. The antigens, however, are T-cell independent and therefore do not result in long-lasting immunity.
Why are capsules advantageous to bacteria?
A durable and dense mucilage covering is the capsule. It gives bacteria protection against the immune system of the host. This protects a bacterial cell from white blood cell absorption and destruction (phagocytosis) and allows it to hide from the host immune system.
How do capsules help bacteria?
Most capsules are hydrophilic (“water-loving”) and may help the bacterium avoid desiccation (dehydration) by preventing water loss. Capsules can protect a bacterial cell from ingestion and destruction by white blood cells (phagocytosis).
Does capsule protect from phagocytosis?
Capsules can protect a bacterial cell from ingestion and destruction by white blood cells (phagocytosis). While the exact mechanism for escaping phagocytosis is unclear, it may occur because capsules make bacterial surface components more slippery, helping the bacterium to escape engulfment by phagocytic cells.
How does the capsule protect the bacteria from immune surveillance?
Due to its exposure to the environment capsules are thought to have roles in the virulence and colonisation of a number of pathogenic bacteria. Capsules can help to prevent bacterial desiccation, foil phagocytosis by host cells or reduce complement-mediated lysis.
How are polysaccharide vaccines made?
Conjugate subunit vaccines (e.g., Haemophilus influenzae type b and pneumococcal conjugate vaccines) are produced by chemically attaching a polysaccharide from the surface of bacteria to a protein molecule through a process called conjugation.
What is polysaccharide antigen?
Carbohydrates in the form of capsular polysaccharides and/or lipopolysaccharides are the major components on the surface of bacteria. These molecules are important virulence factors in many bacteria isolated from infected persons. Immunity against these components confers protection against the disease.
Do polysaccharide vaccines require boosters?
Polysaccharide Meningococcal Vaccines They are poorly immunogenic in infants, do not provide a booster response, do not substantially decrease meningococcal pharyngeal colonization and therefore do not provide herd protection, and can induce the phenomenon of immunologic hyporesponsiveness.
What is the virulence of a microorganism that has a capsule?
The capsule is considered a virulence factor because it enhances the ability of bacteria to cause disease (e.g. prevents phagocytosis). The capsule can protect cells from engulfment by eukaryotic cells, such as macrophages. They also exclude bacterial viruses and most hydrophobic toxic materials such as detergents.