Unit 7 Flashcards
How does bacteria inject proteins into the epithelial cell?
with Invasins
What do these proteins injected into the epithelial cell cause?
Rearrangement of the actin in its cytoskeleton;
Causes membrane to ruffle and the bacteria to be engulfed
What feature of Salmonella prevent it from being phagocytosed?
Flagella
Where do Salmonella pathogens grow and replicate in the infected host?
Inside phagocytes
Where is the site of Shigella attachment in the host?
M cells
How do Shigella cells move between host cells?
They can polymerize actin molecules from the epithelial cells into tail-like structures that propel them from one cell to another
What is the etiologic agent of typhoid?
Salmonella
While investigating a newly discovered Gram-negative bacterium, you find that when the bacteria die, the host experiences severe fever and inflammation. You suspect that the bacterium has __________ in its outer wall membrane.
lipid A
A new drug blocks the adhesins on the surface of a bacterial pathogen. What would likely be the major effect of this drug?
It will prevent infection by this pathogen;
Without adhesins to help them attach to host cells and tissues, pathogens generally cannot resist the defenses of the body long enough to cause an infection or disease.
The suspect agent…
(regarding the demonstration of the etiology of disease)
- must be able to be reisolated from the infected experimental host
- must be isolated and cultured in the laboratory
- must be present in all cases of the disease
- must cause the disease under investigation when introduced into a susceptible host organism
Among the virulence factors produced by Staphylococcus aureus are hemolysin, coagulase, hyaluronidase, and enterotoxin. What factor contribute. to the ability of S. aureus to invade the body?
hyaluronidase
enterotoxin
coagulase
hemolysin
coagulase and hemolysin
hyaluronidase;
an enzyme that breaks down hyaluronic acid, a component of the extracellular matrix, which allows Staphylococcus aureus to spread and invade deeper tissues.
What virulence factors play roles in immune evasion and tissue damage?
coagulase and hemolysin; rather than in direct invasion
What do Coagulase and hemolysin do?
Coagulase: helps form blood clots to protect the bacteria from immune cells
Hemolysin: lyses red blood cells to obtain nutrients
What is Chemotaxis?
The movement of a cell towards or away from a chemical stimulus
What do phagocytes use to move toward microorganisms or damaged cells at the site of infection?
Pseudopods;
often arriving only minutes after infection
Describe adherence
When the plasma membrane of phagocytes attaches to the glycoproteins on the microorganisms surface;
Made easier through Opsonization
What is Opsonization?
A process in which antibodies or complement proteins from the host cell coat the microbes surface serving as “handles”’
Proteins that coat the microbe: Opsonins
Phagolysosome
The structure that results from the fusion of a phagosome and a lysosome
Digestion of most bacteria is complete within ____
10-30 min
Exocytosis is ____
when the phagolysosome fuses with the plasma membrane and expels its contents
What does the plasma membrane of a phagocyte attach to on a microorganism?
Glycoproteins
The process by which a phagocyte moves toward a chemical signal at the site of an infection is called ____
Chemotaxis
What phagocytic processes occurs last in the sequence?
Exocytosis
What is the role of opsonins?
They create “handles” that make it easier for the pseudopods of phagocytes to attach to the microbe invader
How is Streptococcus pneumoniae able to avoid destruction by a phagocyte?
Their capsules make them “slippery” to phagocytes
Which microorganism requires the low pH inside a phagolysosome in order to reproduce?
Coxiella burnetii
What microorganism uses M protein to avoid destruction of a phagocyte?
Streptococcus pyogenes
What is the complement system?
A set of proteins that circulate in the blood serum;
When activated the proteins work together to destroy foreign cells by cytolysis to activate the inflammatory response and assist in phagocytosis
What are the main components of the complementary system called?
C1 through C9
What cellular macromolecules make up the complement pathway?
Proteins
Which of the following is cleaved by C1?
C2 and C4
Where are the complement proteins found in the body?
The blood serum
What is responsible for cleaving C3?
C2aC4b
Which of the complement proteins can directly bind to the surface of a bacterial cell?
C3b
What are the 3 different pathways Complement can be activated through?
- Classical pathway
- Alternative pathway
- Lectin pathway
Classical pathway
- A pair of antibodies attaches to antigens, such as proteins or a large polysaccharide on the surface of the bacterium
- The antibodies bind and activate C1
- C1 then cleaves several copies of C2 and C4
- Together the C2a and C4b fragments form an enzyme that cleaves C3 activating the complement system
Alternative pathway
- 3 complement proteins called factor B, D, & P (properdin) are attracted to microbial cell-surface material such as the lipid carbohydrate complexes of certain bacteria and fungi
- Together with C3 these proteins result in the cleavage and activation of C3 proteins which in turn activate the rest of the complement system
Lectin pathway
- When macrophages ingest material through phagocytosis they release chemicals that stimulate the production of carbohydrate-binding proteins called lectins
- The lectins bind to distinctive patterns of carbohydrates on the surfaces of certain bacteria and viruses
- The lectins themselves can act as opsonins for phagocytosis but also activate C2 and C4 leading to the activation of C3
- Activation of C3 leads to the activation of the rest of the complement pathway
Which of the complement pathways employs properdin?
Alternative pathway
In the classical pathway, which of the following directly activates cellular responses?
C3a, C5a, and C5bC6C7
Antibodies from cellular immune responses are used in ____
the classical pathway
Which of the complement pathways was discovered first?
The classical pathway
What is the function of lectins?
They act as opsonins for phagocytosis
They attach to carbohydrates on some bacterial and viral surfaces, and activate C2 and C4
Chemotaxis and inflammation
C3a and C5a act as chemotactic factors;
attracting phagocytes to the site of infection
They also bind to mast cells triggering the release of histamines and other chemicals as part of inflammation
Opsonization
C3b acts as an opsonin, coating the invading cell
This coat makes it easier for the phagocyte to adhere to the invading cell during phagocytosis
Cytolysis
C5b binds to C6 and C7 which attach to the plasma membrane of the invading cell
C8 and several C9 molecules bind to the C5b-C6-C7 complex forming a cylinder shaped membrane attack complex (MAC)
The MAC’s form circular holes in the membrane of the invading pathogen causing water to enter the cell and ions to leave
This results in Cytolysis, killing the cell
How does cytolysis occur via the complement pathway?
Formation of the MAC in invading cells, killing them
Which complement protein is used as an opsonin?
C3b
If a person lacked the ability to form C5, what direct result of complement could still occur?
Opsonization;
because C3b, a fragment of C3, is responsible for opsonizing pathogens, marking them for destruction by phagocytes
If a person could not form C2, which result of complement would be affected?
Cytolysis, chemotaxis, inflammation, and opsonization;
C2 is a key component in the classical pathway of the complement system. If a person could not form C2, the entire classical pathway would be impaired, affecting all the major outcomes of complement activation
What complement result involves the use of phagocytes?
Chemotaxis and opsonization;
Chemotaxis: refers to the process by which phagocytes are attracted to the site of infection or inflammation
Opsonization: the process where pathogens are marked for ingestion and destruction by phagocytes
The process of diapedesis is important because __________
it allows white blood cells to leave the vessel system and attack pathogens in the tissues.
A microbiologist has isolated a bacterium from the skin and wishes to determine whether it might be a member of the normal microbiota. Which of the following would NOT be evidence for such a conclusion?
- The bacterium is resistant to lysozyme.
- The bacterium produces a large number of virulence factors.
- The bacterium is extremely salt tolerant.
- The bacterium secretes antimicrobial chemicals which inhibit the growth of other bacteria.
The bacterium produces a large number of virulence factors;
A bacterium with many virulence factors would more likely cause disease instead of living cooperatively in the microbiome.
Which of the following statements regarding phagocyte recognition of pathogens is TRUE?
- TLRs on the surface of microbes trigger the accumulation of opsonins.
- TLRs in the phagocyte cytoplasmic membrane bind surface structures of microbes.
- MACs on the surface of microbes are detected by NOD proteins.
- Lectins on the surface of microbes are bound by chemokine receptors.
NOD proteins on the surface of microbes are detected by TLRs.
- TLRs in the phagocyte cytoplasmic membrane bind surface structures of microbes
What are the 3 main functions of inflammation?
- To destroy the agent causing injury
- To limit the effects of the agent on the rest of the body
- To repair or replace damaged tissue
An inflammatory response would result from which of the following?
Jellyfish sting
A headache
Vomiting
Jellyfish sting
If a person turns their ankle, how would one determine if damage to the tissue in the ankle has occurred?
The ankle is red, swollen, and warm to the touch
What is the function of inflammation in response to a burn from a hot iron?
To repair the damaged tissue
What chemicals do damages cells release?
Histamines, prostaglandins, and leukotrienes
What is one function of these chemicals?
(Histamines, prostaglandins, and leukotrienes)
To cause vasodilation;
an increase in the diameter of arteries and arterioles
What does vasodilation result in?
more blood (and therefore more phagocytes, oxygen, and nutrients) being delivered to the site of injury
What does increased blood flow result in when you have an injury?
Redness, heat, and some of the pain associated with inflammation
What do Histamines, prostaglandins, and leukotrienes also have a direct effect on?
The capillaries in the area of the injury;
They cause the walls of the capillaries to open and become leakier allowing more fluid to leave the capillary and enter the tissue spaces causing swelling or edema
What does the increased blood flow after an injury also deliver?
Phagocytes such as monocytes and neutrophils to the scene
What is Margination?
when the phagocytes stick to the walls of the blood vessels;
What is Emigration or diapedesis?
when phagocytes (after Margination) squeeze through the gaps between the cells;
the migration of phagocytes through blood vessels to the site of tissue damage
Within an hour of tissue damage _____
the phagocytes begin to destroy the invading microorganisms by phagocytosis;
After engulfing large numbers of microorganisms and damaged tissue, the phagocytes die, forming pus
Other components of the blood lead to the formation of blood clots which ____
seal off the site of the injury
What is the final stage of inflammation?
Tissue repair;
the increased delivery of nutrients and oxygen from vasodilation aids in this process
What direct effect do histamines and leukotrienes have on capillaries?
They allow capillary walls to open and become leaky
Why is vasodilation important to tissue repair?
It allows for an increased delivery of oxygen, nutrients, and phagocytes to the site of damage
Pus is comprised of ___
dead phagocytes
Which of the following can release histamines?
- The complement system
- Wood from a splinter
- Cells from damaged tissues
- Invading bacterial cells
- Cells from damaged tissues and the complement pathway
- Cells from damaged tissues and the complement pathway
