* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Innate Immune System
Survey
Document related concepts
Drosophila melanogaster wikipedia , lookup
Molecular mimicry wikipedia , lookup
Adoptive cell transfer wikipedia , lookup
Hygiene hypothesis wikipedia , lookup
Polyclonal B cell response wikipedia , lookup
Adaptive immune system wikipedia , lookup
Immunosuppressive drug wikipedia , lookup
Cancer immunotherapy wikipedia , lookup
Immune system wikipedia , lookup
Psychoneuroimmunology wikipedia , lookup
Innate immune system wikipedia , lookup
Transcript
Innate Immune System 1. What are the functions of complement? Opsonisation Lysis of infected cells Disposal of immune complexes (MAC formation) Activation of mast cells (via anaphylotoxins) Chemotactic signalling to recruit phagocytes Also – induction of inflammatory responses 2. Explain the function and mechanism of the classical complement pathway The classical pathway is activated by immune complexes (antigen-antibody complexes). It results in the formation of the classical pathway C5 convertase (C4b2a3b) and the subsequent formation of MAC (C5b6789n), which acts to lyse infected cells. During the cascade, a number of complement fragments are generated (notably C5a and C3b) which play crucial roles in the generation of an immune response. C5a is a potent initiator of inflammation, C3b opsonises cells, encouraging their phagocytosis, and other complement fragments act to recruit phagocytes. 3. What is the lectin pathway? How does it differ from the classical pathway? The lectin pathway feeds into the classical pathway, but differs in its activation. Rather than immune complexes, it is activated by mannose present on the outside of a number of pathogens (worms, viruses, fungi, some bacteria). Activation of MBL (mannose-binding lectin) induces the formation of a complex of MASP1 and 2 and MBL which results in the formation of the classical pathway C5 convertase (C4b2a3b). 4. What is the alternative pathway? The alternate pathway is a primitive complement pathway activated by endotoxin (lipid A) and lipopolysaccharide (LPS) present in the bacterial cell wall of gram negative bacteria (Listeria, a gram positive, also possesses endotoxin – it is the only gram positive bacteria to do so). Activation of this pathway results in the formation of the alternate pathway C5 convertase (C3bBb3b) which then feeds into the final lytic pathway of completment. 5. What are the innate physical defences of the body? Skin Mucous membrane defenses: Tears – lysozymes, phospholipase A Acid Cilia Commensals Saliva – Histatins Surfactant proteins A and D 6. What is the final lytic pathway of complement? What purpose does it serve? C5 is cleaved by either classical or alternate pathway C5 convertase. The C5a fragment is a potent initiator of inflammation. C5b goes on to complex with other complement proteins to form the membrane attack complex MAC (C5b6789n) which inserts into the cell membrane and lyses infected cells. 7. What are phagocytes and what are their functions? What groups of bacteria can avoid their actions? Phagocytes include macrophages, neutrophils, NK cells, eosinophils and basophils. They all ingest foreign pathogens through phagocytosis, a process that is facilitated by opsonisation. The ingested pathogen is held in a phagosome which fuses with a lysosome to form a phagolysosome. The pathogen is then subject to a number of destructive factors including toxic enzymes such as DNAase and acid phosphatase, free radicals including H202, O2-, OH, acidic pH and Nitric Oxide. Some bacteria are able to ameliorate the actions of these factors: pneumococci have a thick capsule which prevents their destruction, staphylococci produce toxins which destroy phagocytes, Mycobacterium TB is able to survive within macrophages, where it induces chronic inflammation and the formation of multinucleate giant cells.