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Immunology 1, Innate Immunity Cells
Interferons: Proteins that…
Immunology 1
Acquired immune system
Characteristics:
Develops after birth, specific (specialised), more potent as it is specific, it has memory and gets better with each encounter with pathogens
Naturally-acquired:
Passive (i.e. antibodies passing from mother to offspring through placenta or breast milk)
Active (antigens enter the body naturally and the body forms antibodies)
Artificially-acquired: Passive (pre-formed, antibodies introduced to your body) Active: vaccines (antigens) they contain either dead or weakened bacteria/virus so that the body has to develop immunity to these pathogens
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Innate immune system
Characteristics:
Present at birth, non-specific (destroys everything), less potent as it is not specific and no memory (response does not get better with each encounter with pathogens)/
Physical barrier: .
- Skin: first line of defence against invading pathogens, contains glands that secrete fatty acids and this creates environment in which bacteria cannot grow
- Mucous and cilia: Goblet cells found along our air pathways produce slimily layers of mucous that traps pathogens. Cilia can then be used to move pathogens to the outside or to. our stomach
- Acidity of stomach: HCl released by parietal cells --> decreases pH in stomach and kills of most pathogens that enters stomach via food or mucous
Inflammation: .
When anatomical barrier is breached, and pathogen enters our tissue, the innate immune system then initiates the process of inflammation. In this process, blood flow is increased to the infected area and it brings several important white blood cells - neutrophils, eosinophils, macrophages and basophils.
Neutrophils: Recruited to the infected area and engulfed bacterial cells and other harmful agents and kill them intracellularly. They can eat up to 20 bacteria before dying.
Basophils: release histamine, which causes dilation of blood vessels leading to the infected area (causing redness). The capillaries in the infected area also become more leaky, which causes edema (swelling).
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Macrophages: Increases blood flow also creates large phagocytes called macrophages that can engulf about 100 bacteria before dying.
Mast Cells: These cells are situated within the tissue and release histamine and other chemicals called cytokines that promote inflammation.
Natural Killer Cell (NK): Although they are not really involved in the inflammation response directly, they do kill off infected cells and cancer cells non-specifically.
When pathogen invades, basophils an mast cells release histamine and other chemicals
Complement System:
- Classical pathway (antigen-antibody complex)
- Alternative pathway (bacterial endotoxin)
- Lectin pathway (mannose-binding lectin)
Effects of complement activation:
- Agglutination
- Bacterial opsonisation
- Chemotaxis
- Direct cell killing
- Neutralisation of viral toxins
- Release of histamine from mast cells and basophils
Alternative Complement Pathway:
Bacterial, Fungal, Viral
Lipopolysaacharides, cell wall, envelope
Binds C3 and factor B --> triggers alternative complement pathway
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Innate Immunity Cells
Interferons: Proteins that interfere with viral replication
Basophils (in the blood) = Mast cells (in the tissues)
Monocytes (in blood) = Macrophages (in tissue)
Kuppfer cells (in liver)
Microglia (in the brain)
Dendritic cells (antigen-presenting cells)
Natural killer (NK) cells - kills cancer cells, infected cells