Final Exam 1 Flashcards
Hyaluronidase
Enzyme produced by a pathogen after attaching to host epithelium. Pathogen invades deeper tissues.
Hyaluronic acid
A polysaccharide that maintains organization of cells in host tissues
coagulase
An enzyme produced by the pathogen that causes clots to form around the infection site to protect the pathogen from immune cells. Coagulates fibrin
Immune cells will see the clos as normal, leave the pathogen inside inside the clot alone and thus then the pathogen can grow and divide
Streptokinase
(staphylokinase) dissolves clots to allow the pathogen to move into deeper tissue layers and the blood stream.
So this is an enzyme that is produced by the pathogen
AB-type exotoxins
Two-component toxins
B-subunit binds host cells (cell receptors) and facilitates the transport and release of the A-subunit into the host cell
The A-subunit has toxic activity. Enzymatic interruption of transcription, translation, cell signalling, etc. Action part!
Lots of organisms produce AB toxins
Diphtheria
Respiratory disease
Corynebacterium diphtheriae colonizes throat and upper respiratory tract
A buildup of fibrin clots, dead cells, and an immune response result in typical swelling of the neck and pseudomembrane formation in the throat. - can occlude the airway and cause death
Fatal if untreated (suffocation) or if the toxin (Diphtheria toxin) spreads to the heart, liver etc
DTaP vaccine
What bacterium causes Diphtheria?
Corynebacterium diphtheriae
DTaP vaccine
Diphtheria, tetanus, and pertussis vaccine
Diphtheria toxin
DT is the best studied bacterial toxin.
The Tox gene is located on a lysogenic bacteriophage β
- An AB type toxin
DT ADP ribosylates (elongation factor 2) EF-2, which stops translation - leading to host cell death (inhibits protein synthesis) - (DT catalyzes the addition of ADP to EF-2 - EF-2 ADP then blocks the elongation step of translation because EF-2 is inactivated)
Botulism
A neuromuscular disease that results when Clostridium botulinum either colonizes the GI tract or the toxin is ingested
Toxin is absorbed in stomach/small intestine and enters the blood stream where it targets motor neurons at neuromuscular junctions
The toxin produce makes it so that muscles cannot be contracted - flaccid paralysis
Treatment via antibiotics and antitoxin, but once the toxin is bound to its target, there is no treatment.
Mechanical respirators for breathing, death
Botulism Toxin (BoNT)
BoNT is the most potent bacterial toxin known.
Bot genes are located on the chromosome, plasmids, and prophage
An AB-type neurotoxin
B-subunit binds a host cell membrane receptor on motor neurons and translocates the A-subunit into the host cell
The various BoNT A subunits are endoproteases that cleave various SNARE proteins
SNARE proteins are required for exocytosis of NT
Synaptic vesicles thus can’t merge with the cell membrane to release ACh into the synaptic cleft where they normally initiate muscle contraction because the cleaved SNARE proteins are not functional
Muscles don’t contract without ACh binding
Digestion affected first, then limb problems, then breathing.
Tetanus
A neuromuscular disease that results when Clostridium tetani colonize a deep tissue wound (anaerobic).
Toxin diffuses away from the wound site and enters the blood stream where it targets the inhibitory neurons of motor neurons
causes spastic paralysis (lock jaw) - host cannot relax contracted muscles)
Treatment via antibiotics and antitoxin, but once toxin is bound to target, there is no treatment (6 month last)
DTaP vaccine
Tetanus toxin (TeNT)
Shares homology with BoNT, but targets different receptors
Tet genes located on a plasmid
An AB neurotoxin.
B subunit binds to host cell membrane receptor on inhibitory neurons and translocates the A-subunit into the host cell
A TeNT A-subunit is a endoprotease that cleaves the SNARE protein: synaptobrevin-VAMP
cleaved SNARE protein means that synaptic vesicles containing glycine cannot merge with the cell membrane to release glycine. Glycine normally inhibits motor neurons so when glycine is no longer released, the motor neurons will always be releasing acetylcholine and muscles will be in a constantly contracted state.
Cholera
An intestinal disease caused by Vibrio cholerae colonizing the small intestine.
Exposure to food and/or water contaminated with human feces.
Toxin targets intestinal epithelial cells
Causes severe diarrhea associated with life-threatening dehydration (cholera cots)
treatment by rehydration therapy and antibiotics
Rice water stool - diarrhea contains globs of membranes, mucous, and other cellular debris
Cholera Toxin (CT)
Shares homology with enterotoxins of pathogenic E. coli and Shigella
ctx gene is on a prophage
CT toxin is a hexameric AB-type toxin (AB5)
The B subunit finds to a host cell membrane receptor on intestinal epithelial cells and translocates the A-subunit into the host cell.
The CT A-subunit ADP ribosylates the alpha subunit of Gs proteins. Leads to constitutive activation of Gs and AC which increases cellular cAMP – activates PKA pathways
RESULT: cells top absorbing Na+ and Cl-, and PUMP Cl- and HCO3- into the gut lumen – water then rushes out of cells
Cytolytic exotoxins
Cytotoxins
Secreted toxin proteins that lyse cells - main role is to destroy cells to make nutrients available for the pathogen
ex. hemolysins
They function by using phospholipases
Some form pores in our cell membranes, causing them to lyse
Grangrene
skin tissue disease that results when Clostridium perfringens colonizes wound sites
Exposure via contaminated soil
Has an a-toxin that is a cytotoxin/phospholipase that causes necrosis in the wound.
The bacterium metabolizes released sugars and proteins- Mixed acid fermentation
Can lead to amputation
Treatment via antibiotics and debridement
Staphylococcus aureus alpha-toxin
cell destruction by S. aureus skin infections mediated by this toxin (an alpha hemolysin)
Toxin is a pore-forming cytotoxin (electrolyte balance kills the cells)
Accumulation of dead cells in the area forms pus
Treatment via antibiotics and drainage
Superantigens
Excreted toxin proteins that induce a massive immune response - toxins bind to immune cells and activate them in a non-specific manner (activate 20%)
- Normal pathogens/toxins activate 0.0001-0.001%….
The massive immune response induces high fever, low blood pressure, organ disfunction/failure, system shock (severe multiorgan failure) and death
ex.
S. aureus
- Toxic shock syndrome (TSST-1)
- Staphylococcus enterotoxin (food poisoning)
Streptococcus pyogenes
- Exotoxin A (scarlet fever, rheumatic fever) strep throat
- septocemia can occur
Indiscrimately activates helper T cells - ie complex is formed without the specific match. So get massive amounts of cytokines released that result in a cytotoxic storm - toxic shock
Toxic Shock Syndrome
Causes by TSST-1 produced by Staphylococcus aureus that enters the blood stream
Endotoxins
-part of the pathogen cell structure
- More prevalent when the pathogen is in higher concentration (more toxin present)
The IS responds by releasing pyrogenic (fever) cytokines, as well as causing an increase in heart rate, diarrhea/vomiting, low blood pressure, and inflammation.
large quantities of endotoxin can result in blood clotting, organ disfunction/failure, endotoxic shock (septic shock) and death
- Lipopolysaccharide (LPS) in gram negative - LIPID A
- Lipteichoic acid (gram positve ) - endotoxins
Lipopolysaccharide
Makes up the outer half of the outer membrane in Gram Neg cells. Lipid A is the endotoxin
The polysaccharide portion makes the molecule soluble
Induces fever and general inflammation
Large doses can cause tachycardia, blood coagulation
immunology
is the study of the components and processes used to resist pathogens and fight disease
immunity
the ability of an organism to resist infection
The innate immune system
The automatic ability to recognize and destroy a pathogen (or its products)
Fast (hours)
Does not require previous exposure, no memory
Sometimes all that we need to fight an infection
Reduces exposure, adherence, colonization and invasion of pathogenic organisms.
ie barrier defenses are included as well.
Adaptive (specific immunity)
The second line of defense
The acquired ability to recognize and destroy a specific pathogen or its products
Following infection, effectors learn to target a particular pathogen to generate a coordinated response
Slower (days)
Generates immune memory
Blood to lymph
The fluid that leaves the blood vessels is called lymph. In capillary beds, lymph drains out of blood vessels, floods the tissues and then drains into lymphatic capillaries which then go to lymphatic vessels which then go to lymph nodes.
Lymph re-enters the blood stream around the neck area.
Lymph nodes
Sampling ground
Lymphocyte-filled tissues that sample the lymph for pathogens, toxins, activated immune cells
Spleen
Lymphocyte filled tissue that samples blood for pathogens, toxins, activated immune cells
SCREENS THE BLOOD
Mucosa-Associated Lymphoid Tissues (MALT)
Patches of lymphocyte-filled tissue that sample the mucosa for pathogens, toxins, activated immune cells
ie any mucous layer exposed to the environment (GI tract, lungs)
What are the primary lymphoid organs?
The Bone marrow and the thymus where lymphocytes develop
Hematopoiesis
Process by which hematopoietic stem cells, in the bone marrow, differentiate into more specific cell types
- Stem cells are activated by cytokines
Form erythrocytes, leukocytes (0.1% of cells formed)
HSCs differentiate into
- lymphoid precursor cells (cell and antibody-mediated immunity)
- myeloid precursor cells (phagocytosis and inflammation)
Myeloid precursors become
-Mast cells
-Basophils
-Eosinophils
-Neutrophils
-Monocytes (Macrophages, Dendritic cells)
Antigen presenting cells
Dendritic cells
Macrophages
B cells
Granulocytes
Neutrophils, Eosinophils, Basophils, Mast cells
Which cells are involved in phagocytosis?
Dendritic cells, macrophages, neutrophils, eosinophils
Which cells are involved in the inflammatory response?
basophils, mast cells
Cells in innate immunity?
all cells from the myeloid precursors plus natural killer cells