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Describe the parts of the lymphoid system
- Lymphoid system-
- Tissues and organs that help B and T cells to come into contact with all antigens that enter the body
- Lymphatic vessels carry a fluid called lymph which comes from the blood to lymph nodes where it is screen for antigen and returned to blood
- Secondary Lymphoid tissue
- Spleen, lymph nodes, tonsils, adenoids, appendix, SALT(skin), MALT(mucosa)
- Organs that allow B cells and T cells, dendritic cells to exchange information
- Primary Lymphoid organ
- Bone marrow-hemaopoietic stem cell for T and B cells (B cells are mature marrow)
- Thymus-where T cells mature
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a.k.a immunoglobulins (abbreviated Ig), they are glycoproteins, several classes.
Antibodies
(MADGE) IgM, IgA, IgD, IgG, and IgE
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Classes of Antibodies IgM
IgM - first antibody produce in response to an infection, Pentamer-five y shaped, too large to get into tissues, highly effective at activating complement and at agglutination
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Antibodies IgG
IgG - 80-85% of the antibodies in the blood, first and most abundant class made during secondary response, it can cross into tissues, can also cross the placenta-helps protect fetus and the baby after birth for the first 3-6 months, present in breast milk-first produced called colostrum
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Anti-bodies IgA
IgA - secretory IgA found in the mucosa-helps bind microbes and trap them in the mucosa, found in breast mil-does not absorb into the infants bloodstream but does help protect the intestinal tract
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Antibodies IgD
IgD - function unknown
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Antibodies IgE
- IgE - not found in high quantities in the blood
- binds to mast cells and basophils (two cell types important in allergies and clearing parasitic worms) two adjacent IgE molecules have antigen bound-triggers the basophil or mast cells to release their granules of histamine, sometimes also binds to allergens-allergic response
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two organisms live in close together on a permanent basis
symbionts
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one organism benefits and the other is unaffected
commensalisms
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both organisms benefit
mutualism
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one organism benefits and other is damaged
parrsitism
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Koch's postulates - developed a system to determine if an microbe causes illness.
Microorganism must be present in every case
Must be able to grow the organism in pure culture from host blood/tissues
Pure cultures of the organism must cause disease in susceptible hosts
Organism must e recovered from the experimentally infected host
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Molecular postulates
The virulence factor gene (or gene product) must be present in disease causing strains but not in strains that do not cause disease (avirulent)
Introducing the virulence gene to an avirulent strain should make it become virulent
Virulence genes must be expressed during the disease
Antibodies or immune cells specific for the virulence gene product should be protective
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Establishment of an Infection includes:
Adherence - attach to host cell surfaces
Colonization - must be able to overcome the normal flora and host defenses - in order to divide and grow
Invasion Penetration of the skin-wounds, penetration of mucus membranes
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Invasion includes:
Induce phagocytosis in an epithelial cell release molecules onto host cels surface cause ruffling and endocytosis (non-professional phagocytes)
Using antigen sampling cells MALT uses specialized cells called M cells to sample areas of the body
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Ways of Avoiding Host Defenses
Hide in a host cell
Inactivating complement
Avoiding/surviving Phagocytosis
Avoiding antibodies many ways to do it
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Avoiding Antibodies
IgA protease-breaks down IgA
Antigenic variation-change the outer surface molecules so any antibody that used to be able to bind no longer will
Mimic host cells have outer surface structure or molecules that resemble host molecules-fool immune system into treating the microbe like self
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Proteins secreted outside the cell that cause very specific damage to host
Exotoxins
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Types of Exotoxins:
Neurotoxins - damage nervous systems (botulism toxin is an example)
Enterotoxins - exotoxins that damage the digestive tract
A-B toxins - B portion of toxin binds to the host cell and A portion is the portion that causes damage
Membrane damaging toxins - damage cell membranes causing them to lyse/hemolysins-membrane damaging toxins that disrupt RBC membranes/Phospholipases remove the phosphate heads from lipid bilayer
Superantigens - circumvent the specificity of the T cell response
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antibodies bind antigen, they tend to clump together (agglutination)
Antigen-antibody complexes
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occasionally antibodies made to foreign molecules will also accidentally bind to our own self molecules-autoimmune response ensues
Cross-reactive antibodies
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Describe the basic anatomy of the respiratory tract, including the mucociliary escalator.
The respiratory system has two general parts-the upper respiratory tract and the lower respiratory tract. The upper respiratory tract includes the nose and nasal cavity, phaynx (throat), and epiglottis. Mucous membranes line the respiratory tract. Mucociliary escalator keeps the lower respiratory tract completely free of microorganisms. The lower respiratory tract includes the larynx (voice box), trachea, bronchi, and lungs.
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