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21 Cards in this Set
- Front
- Back
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The two types of phagocytic cells: |
Monocyte derived macrophages - -Large macrophages (phagocytes) - Long lived ones contain mitochondria - remove foreign materials such as dead b.c Polymorphnuclear granulocytes - Produced in bone marrow - Nucleus is lobulated - Granulocytes - neutrophils (phagocytic), eosinophils, basophils - Agranulocytes - monocyte |
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Steps of phagocytosis: |
1) Binds to receptors (e.g C3B) 2) Taken in by vacuole 3) Lysosomes fuse with lysosome = phagosome and release digestive enzymes 4) Digestive enzymes released into phagosome - killing contents - before breaking down and excreting |
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The 3 types of complement activation |
Classical Alternate Lectin/acute phase proteins |
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Result of cytokines |
Stimulates/inhinits normal cell function, stimulates proliferation, regulates innate defences. |
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What do interferons do? |
Antimicrobial cytokines that interfere with viral replication. Induces synthesis of antiviral molecules. |
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The two phagocyte killing mechanisms: |
Oxidation - Hydrogen peroxide, free hydroxide radicals Non-oxidation - Substances such as cathespin G, defensins, cationic proteins, lactoferrin, lysozyme. |
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What is MHC |
Pathogen enters the cell, releases proteins whic bind to MHC-I. Cytoxic T cell binds responds to MHC-1, releasing cytokines and killing the cell. |
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Helper t cells |
Macrophage takes in phagocyte and forms a phagosome with MHC-2. CD4 - Activates helper T cell, causing proliferation and differentiation. CD8 - Activates cytotoxic T cells then migrates to activate the effector cells. |
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Natural killer cells |
Kills intracellular pathogens in the absence of MHC. |
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How are large microbes killed? |
ADCC - antibody dependent cellular cytotoxicity Antibodies recognise and bind to the parasite. Fc region attracts immune cells. - Release of O2 NK release granzymes Eosinophils release perforins |
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How are B cells activated |
Without helper T cells - Recognize via PRRs or by repeating antigen determinants. or activated by MHC-II |
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How are T cells activated? |
IDC's present antigen to MHC II and cause activation. OR Needs: 2x signals 1) Antigen recognition by TCR and CD4/CD8 of antigen MHC-1 2) Activation of helper t cells or cytotoxic t cells |
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What are the activities of a cytotoxic T cell. |
Activation of intracellular killing mechanisms (cytokines, IFNy) OR directly attacks using perforin, granulysin. OR destroys vital tissue |
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Pathogen |
A microbe able to cause disease. |
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Pathogenicity |
The ABILITY of an infectious agent to cause disease. |
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Virulence |
A quantitative measure of pathogenicity. |
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Virulence factors: |
The various genetic, biochemical or structural features of a pathogen which enable it to cause disease. |
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What do bacterial invasins do? |
Localised production of enzymes by bacteria which degrades components of biological barriers. Bacteria that produce invasins are capable of systemic spread. |
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Endotoxins: |
Cell wall component - LPS Quite stable Can't form toxoids Less potent, low specificity GRAM -ive only Regulated by chromosomal genes |
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Exotoxins: |
Soluble proteins Gram +ive or -ive Generally located on plasmids Proteins - have two units: A- toxic B- bind and activate A Unstable, can form toxoids Very potent and very specific Doesn't usually produce fever. |
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6 steps : |
1. Attachment and entry into the body 2. Local or general spread into the body 3. Multiplication 4. Evasion of host defences 5. Shedding from the body 6. Cause damage in host. |
