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Immune System - Coggle Diagram
Immune System
Antibodies
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Structure of antibody : y shaped, 4 polypeptide chains, 2 regions
After antibodies kill a pathogen the number is reduced and they no longer stay in the blood. When the body is reinfected antibodies need to be made and due to the memory cells antibodies can be produced quicker and in a larger quantity.
Antigen :A foreign molecule which triggers an immune response, often a protein or long polysaccharide. Human cells also have these, but they are recognized by the immune system as self.
After B cells arw activated they divide to produce plasma cells which all produce the same antibodies—this is called clonal selection --> A small number of clones become memory cells which last long after infection, allowing for a fast secondary immune response upon reinfection
B lymphocytes are activated when Pathogens are ingested by macrophages, displaying the antigens in the plasma membrane. Helper T-cells have antibody-like receptor proteins to bind to the antigens, but only a few will fit the antigen. The T cells that fit are activated, and they go to a B cell with the right receptor for the antigen.The helper T cell activates the B cell by binding and releasing a signalling protein
Vaccines
Vaccinations induce long-term immunity to specific pathogenic infections by stimulating the production of memory cells
A vaccine is a weakended form of the pathogen that contains antigens but is incapcbale of triggering a disease. The antigentic determinants in a vaccine may be conjugated to an adjuvant which functions to boost the immune response
The body responds to an injected vaccine by inittiating a primary immunue response, which results in memory cells being made.
When exposed to the actual pathogen , the memory cells trigger a more potent secondary immune repsonse --> as a ocnseweunce of thise more potent immune response, disease symptoms do not develope
Length of immunity is dependent on how long the memory cells survive for ; memory cells may not survive a lifetime an individual may subsequently require booster shot to maintain immunity
Herd Immunity : Vaccination confers immunity to vaccinated individuals but also indirectly protects non-vaccinated individuals via her immunity --> herd immunity is when individuals who are not immune to a pathogen are protected from exposure by the large amounts of immune individuals within the community
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Antibiotics
Antibiotics are compounds that kill or inhibit the growth of microbes (specifically bacteria) by targeting prokaryotic metabolism
Metabolic features that may be targeted by antibiotics include key enzymes, 70S ribosomes and components of the cell wall
Because eukaryotic cells do not possess these features, antibiotics will target the pathogenic bacteria and not the infected host
Antibiotics may either kill the invading bacteria (bactericidal) or suppress its potential to reproduce (bacteriostatic)
Viruses do not possess a metabolism (they are not alive) and instead take over the cellular machinery of infected host cells
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The prevalance of resistant bacterial strains is increasing rapidly with human populations due to a number of factors:
Antibiotics are often over-prescribed (particularly broad-spectrum drugs) or misused (e.g. given to treat a viral infection)
Many antibiotics are freely available without a prescription and certain antibiotics are commonly included in livestock feed
Multi-drug resistant bacteria are especially common in hospitals (i.e. nosocomial infections) where antibiotic use is high
Pathogens
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Examples of pathogens
Bacteria (E.g E.Coli) : Prokaryotes, no real nucleus, divide by Binary fission. Bacteria can cause food poisoning, ear and eye infections, cholera and diarrhea
They are unicellular prokaryotic cells that can reprodcue quickly and compete with host cells for space and nutrition ; most are harmless and actually form a mutualsitic relationship with the host. Bacteria may cause disease by producing toxic compounds (exotoxins) or releasing the substances when destroyed (endotoxins)
Viruses ( E.g HIV) Acellular, needs a host cell to carry out functions of life such as reproduction. Viruses and can have DNA or RNA and they mutate evolve and recombine quickly. Viruses can cause flu, herpes, smallpox, and Ebola.
They can be DNA based ( adenoviruses) or RNA-based ( retro viruses). They usually consist of an inner core nucleic acid surrounded by a protein coat ( capsid)
Fungi ( E.g Epidermophyton) : Fungi are Eukaryotes that reproduce with spores. They can cause Athletes food, mould, ringworm, allergic reactions and respiratory problems
Fungi attacks the body surfaces like skin and mucous membranes. Most fungi are moulds. Moulds consist of branching filaments called hyphae , which may form a mass of invading threads called mycelium
Protozoa ( Malaria Parasite) : Protozoa are parasites that can cause disease such as malaria , Leishmaniasis and Toxoplasmosis.
Parasites can be classed as either ectoparasites (living on the surface of the host) or endoparasites (living within the host). Endoparasites can include microparasites (e.g. single-cell protozoa) or macroparasites (multicellular helmithes). A parasite is an organism that grows and feeds on an organism to the detriment of the host’s survival
Prions
A prion is an infectious protein that has folded abnormally into a structure capable of causing disease.Prions can cause normally folded proteins to refold into the abnormal form and hence propagate within a host body
Prion proteins aggregate together to form amyloid fibres that cause holes to form in the brain (spongiform encephalopathy). Infectious prion proteins have a higher beta-sheet content, making them more resistant to denaturation and difficult to treat
Barriers
The Skin and Mucous membranes form a primary defence against pathogens that cause infectious diseases. (Non-specific Defences --> Innate immunity)
Mucous Membranes: Sticky Mucus traps invaders, pH generates an environment not suitable for certain pathogens, Lysozyme allows enzymes to break down pathogens, Natural organisms conduct competitive exclusion by non-harmful microbes
Skin : As the skin is continuous it is hard for pathogens to find an opening to penetrate. Additionally there are several tough layers and the skin is relatively try.Similar to Mucous Membranes, the pH is not favorable to pathogens and lysozyme enzymes break down pathogens and natural organisms conduct competitive exclusions by non-harmful microbes
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Leukocytes
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The second line of defense against infectious disease is the innate immune system ( non specific response). Phagocytic white blood cells are an integral component of this line of defense as they engulf and digest foreign bodies. Phagocytic leukocytes circulate in the blood and move into the body tissue ( extravasation) in response to infections. Damaged tissues release chemicals, such as histamine, which draw white blood cells to the site of infections. Pathogens are then engulfed when cellular extensions , pseudopodia, surround the pathogen and then fuse to form an internal vesicle. The vesicle is then fused to a lysosome forming a phagolysosome) and the pathogen is digested - pathogen fragments ( antigens) may be presented on the surface of the phagocyte in order to stimulate the third line of defense.
Methods of Transmission
Pathogens can be transmitted through several manners : For example the influenza virus is spread through inhaled droplets, Herpes is transmitted through direct contact, Strep throat and HIV are transmitted through bodily fluids, Rabies (virus) and Malaria ( protozoa) are transmitted through animal vectors, Hepatitis B ( virus) is transmitted through blood contact and Salmonella is transmitted through ingestion