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Mechanism of Disease

Terms in this set (17)

YouTube Notes at: https://youtu.be/amdZH19X3y0
and Part 2: https://youtu.be/LTSRLVRzW-o
www.sciencewithsusanna.com has a blank drawing, notes, and practice questions.
All microbes that are on our body must do to things to "get to stay". What are these two things?
1. ADHERE - glycocalyx and fimbriae help bacteria with this; viruses capable of infecting humans have proteins that allow them to bind to receptors on our cells
2. AVOID OUR IMMUNE SYSTEM - which often means avoid phagocytosis by WBCs.
In addition to adhering and avoiding phagocytosis, pathogens must be able to:
somehow damage our cells.
Antigenic variation
Pathogens alter their surface proteins (and antibodies are rendered ineffective). Influenza virus is notorious for this; so are protists such as Plasmodium (causes malaria) and most parasitic worms.
bacterial capsule function
*Avoid desiccation (drying out)
*increase resistance to phagocytosis
*increase adhesion to solid surfaces.
Coagulase
*enzyme produced by Staphylococcus aureus
*promotes blood clotting (coagulation)
*walls off the site of infection from WBCs; (example: boils)
waxy cell wall
Mycobacterium
*prevents dessication and helps bacteria survive in droplet aerosols
*helps this bacteria to survive INSIDE of our WBCs!
Why might secretion of immunosuppressive chemicals be useful for both a parasitic worm and its host?
*decrease inflammation and/or reduce the likelihood of an autoimmune reaction in the host
*helminth gets a place to live
normal flora
*reside in/on the body without causing disease
*take up "parking spaces" in your gut and on your body to crowd out pathogens, especially yeast on the skin and intestinal-damaging pathogens in the gut.
opportunistic pathogens
Often part of normal flora when kept in balance, they can cause disease when the host's defenses are compromised or when they grow in part of the body that is not natural to them
exotoxins
-Secreted by pathogens:
*cytotoxins - destroy cells
*neurotoxins - interrupt or overstimulate normal signaling at synapses
*enterotoxins - cause diarrhea
Streptococcus pyogenes' cytotoxin
Beta-hemolytic - destroys red blood cells if it gets into the bloodstream
Clostridium Neurotoxins
Summary - Botulism causes paralysis; tetanus causes sustained contractions.
C. botulinum - blocks acetylcholine release at the neuromuscular junction, resulting in paralysis - most frightening if it stops diaphragmatic contraction and the patient can't breathe
C. tetani -this neurotoxin makes its way up to the central nervous system and blocks GABA (an inhibitory neurotransmitter) from stopping normal muscle contraction. Thus, the end result is too much contraction (the opposite effect of botulism).
superantigen
a class of antigens that cause non-specific activation of T-cells resulting in polyclonal T cell activation and massive cytokine release
Cytokine Storm
Overproduction of inflammatory signals that damage our OWN organs
*Causes fever and body aches
*Septic shock
*Also may lead to disseminated intravascular clotting (DIC)
Disseminated Intravascular Coagulation (DIC)
Complex disorder in which clotting and hemorrhage simultaneously occur. Basically all the platelets and clotting factors get used up in little peripheral clots; meanwhile places that need clotting factors bleed inappropriately.
Endotoxin
a toxin that is part of Gram negative bacterial cell wall and is released when the cell dies or multiplies. It can result in a cytokine storm.
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