Which of the following defense systems would be involved in fighting a viral pathogen?
According to the animation, antibodies interact with which innate defenses?
Phagocytosis and the complement system
Mycobacterium tuberculosis is an intracellular pathogen of humans. After being ingested by a macrophage, it prevents formation of the ___________ by preventing fusion of the phagosome with the ___________________.
In which intracellular compartment would you expect most of the digestive enzymes involved in pathogen destruction to be found?
In macrophages and dendritic cells (so-called antigen-presenting cells) some small parts of the phagocytosed particle are presented to other cells of the immune system. If you were to draw an arrow leading to "antigen presentation" as described above, from which word would it extend?
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.
Which of the following can release histamines?
Cells from damaged tissues and the complement pathway
The first to be discovered, is initiated when antibodies bind to antigens (microbes) and occurs as follows
1. antibodies attach to antigens, forming antigen-antibody complexes. The antigen-antibody complexes bind and activate C1
2. next, activated C1 activates C2 and C4 by splitting them, C2 is split into fragments called C2a and C2b, and C4 is split into fragments called C4a and C4b
3. C2a and C4b combine and together they activate C3 by splitting it into C3a and C3b. The C3 fragments then initiate cytolysis, inflammation and opsonization
when microphages ingest bacteria, viruses, and other foreign matter by phagocytosis, they release cytokines that stimulate the liver to produce lectins, proteins that bind to carbohydrates.
In the classical pathway, which of the following directly activates cellular responses?
C3a, C5a, and C5bC6C7
Which of the following are functions of lectins?
They act as opsonins for phagocytosis, they attach to carbohydrates on some bacterial and viral surfaces, and they activate C2 and C4.
How does cytolysis occur via the complement pathway?
Formation of the MAC in invading cells, killing them
If a person could not form C2, which result of complement would be affected?
Cytolysis, chemotaxis, inflammation, and opsonization
A response that is uniquely directed against pathogenic Bordetella pertussis would involve what component?
First line defenses have what aspect in common with each other?
They are physical barriers against invading pathogens.
Both the innate and adaptive defenses of the immune system work to prevent
the penetration and colonization by pathogens, and the diseases they cause.
If a new bacterial pathogen entered a human body through an accidental needle stick, the first cell that would try to kill the pathogen would likely be
The process by which a phagocyte moves toward a chemical signal at the site of an infection is called
What is the role of opsonins?
They create "handles" that make it easier for the pseudopods of phagocytes to attach to the microbe invader.
A protein that covers the surface of an invading microbe, making it easier for the phagocyte to ingest.
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?
Which of the following microorganisms use M protein to avoid destruction of a phagocyte?
How is phagocytosis in the immune system different from protozoan phagocytosis?
Protozoan phagocytosis is used for feeding; phagocytosis by immune cells is used to fight infection.
Select the cell types that are actively phagocytic.
Macrophage,Neutrophil, Dendritic cell, Eosinophil
Phagocytosis is a multistep process that begins
the phagocyte moves toward the microbe, establishes contact with the microbe
then engulfs, digests, and discharges residual wastes.
The first line of defense
intact skin, mucous membranes and their secretions, and the normal microbiota.
Phagocytosis is the process through which
one cell engulfs extracellular material, such as an invading microorganism
steps of phagocytosis in the correct order
1)chemotaxis of phagocyte to microbe occurs
2)phagocyte adheres/attaches to microbe
3)pseudopods of phagocyte engulf and internalize the micrboe, forming phagosome
4)lysosome fuses with the phagosome forming phagolysosome
5)digestion of microbe occurs within phagolysosome
6)indigestible material is discharged
The movement of phagocytes is described as
ameboid motion because it resembles the movement of amebae (which are protozoans). This movement involves elements of the cytoskeleton of the phagocyte, specifically the microfilaments
The lengthening or shortening of the microfilaments is what enables
pseudopods to extend and retract.
What might interfere specifically with chemotaxis of a phagocyte?
Defective microfilament function
Absence of cytokine and complement receptors on phagocyte surfaces
Capsules serve as
important microbial virulence factors
interfere with phagocytosis by blocking attachment of phagocyte Toll-like receptors to microbial PAMPs
M protein is a virulence factor of Streptococcus pyogenes that can specifically interfere with phagocytosis by
blocking adherence of the phagocyte to the streptococcal cells
Some bacteria secrete enzymes that cause host proteins to be deposited on their surface, making them appear as "self" to the host.
facilitate the binding of phagocytes to the microbe via C3b receptors on the phagocyte surface
Complement peptides, particularly C3b
select strategies from the list provided that might enable a microbe to avoid or escape phagocytosis or phagocytic killing.
Microbe prevents fusion of phagosome with lysosome to form phagolysosome.
Microbe produces leukocidin.
Microbe escapes from phagosome prior to fusion with lysosome.
A capsule surrounds the microbe.
This activity asks you to think specifically about the process through which phagocytes kill and digest microbes and to identify steps of the process that might be compromised and interfere with this killing activity.
Defective oxidative burst
Defective microtubule function-
Defective microtubule function
First, the phagosome must fuse with the lysosome. This process is enabled by microtubules, which facilitate the movement of organelles within cells. Defective microtubule function would likely prevent the formation of phagolysosomes
Phagocytic cells may show an oxidative burst but be unable to produce hypochlorous acid; as a result, the phagocytes' ability to kill the microbes is compromised.
Defective oxidative burst
Chronic granulomatous disease is an inherited disorder in which the oxidative burst process is defective and phagocytic cells are unable to effectively kill the microbes they phagocytize. As might be expected, this disease is characterized by repeated serious infections
Based on the animation, which of the complement proteins can directly bind to the surface of a bacterial cell?
What is the role of helper T cells in the adaptive immune response?
Helper T cells activate B cells and cytotoxic T lymphocytes to kill infected host cells. Helper T cells activate B cells that are displaying antigen, causing clonal expansion. Helper T cells also activate cytotoxic T cells, which will search for and destroy infected host cells.
What is meant by the clonal expansion of a B cell?
An activated B cell divides into cells that give rise to memory B cells and plasma cells. The activated B cell divides until there are many clones. Some differentiate into memory cells, other become plasma cells that produce and secrete antibodies.
The student who caught the cold caused by this specific Rhinovirus was exposed to the exact same Rhinovirus 18 months later. What component of the immune system will protect her from getting the same cold again?
Memory B cells. Memory cells to that specific virus are stored in the lymph nodes for many years. When the student comes into contact with this specific Rhinovirus, these memory cells quickly divide and differentiate into antibody-producing plasma cells. The antibodies will prevent the virus from reaching an infectious titer (number that causes infection).
Correctly order the steps involved cellular immunity:
1. The Tc recognizes the infected host cell
2. The Tc interacts with epitope presented by MHC-I on the dendritic cell
3. The Tc secretes perforin and granzyme, causing apoptosis
4. The helper T cell activates the Tc cell
Which of the following is not a step used by cytotoxic T cells to kill infected host cells?
Recognition of infected host cell using its CD4 glycoprotein
Place the following steps of phagocytosis in the order that they occur:
1. Endosome fuses with lysozome
2. Dendritic cell engulfs Rhinovirus
3. Epitopes are attached to MHC-II
4. Digestion of the Rhinovirus
5. MHC-II plus the attached epitope move to the outside of the dendritic cell
Activation of cytotoxic T cells by helper T cells
The activation of cytotoxic T cells leads down the path of cell-mediated immunity
A person who has AIDS contracts rare and often life-threatening infections because their helper T cell count is so low. Which of the following components of the immune response still respond to antigen despite the low helper T cell count?
Clonal selection of B cells. B cells can still bind to antigen, which is the process of clonal selection. However, without a helper T cell, clonal expansion and antibody production will not occur.
Adaptive defenses include both humoral and cellular immunity.
Adaptive defenses are operating optimally when both humoral and cellular immunity are working together in response to a pathogen.
Which of the following is a step used by cytotoxic T cells to kill infected host cells?
Secretion of granzyme
Secretion of perforin
Recognition of infected host cell using its TCR