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Mucous membranes are a part of

innate defense.

According to the animation, B cells interact directly with

helper T cells.

Which of the following defense systems would be involved in fighting a viral pathogen?

T lymphocytes

According to the animation, antibodies interact with which innate defenses?

Phagocytosis and the complement system

Which cells directly attack abnormal cells in the body?

Cytotoxic T cells

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 ___________________.

phagolysosome, lysosome

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.

Diapedesis is

the migration of phagocytes through blood vessels to the site of tissue damage.

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?

Cells from damaged tissues and the complement pathway

Which of the complement pathways employs properdin?

Alternative pathway

Classical 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

Lectin pathway

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

Antibodies from cellular immune responses are used in

the classical pathway.

Which of the complement pathways was discovered first?

The classical pathway

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

Which complement protein is used as an opsonin?


If a person lacked the ability to form C5, what result of complement could not occur?



refers to the movement of a cell in response to a chemical stimulus


enhancement of phagocytosis by coating with C3b

If a person could not form C2, which result of complement would be affected?

Cytolysis, chemotaxis, inflammation, and opsonization

What complement result involves the use of phagocytes?

Chemotaxis 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

a phagocyte.

an antibody-producing cell.


a cytotoxic T cell.


What does the plasma membrane of a phagocyte attach to on a microorganism?


The process by which a phagocyte moves toward a chemical signal at the site of an infection is called


Which of the following phagocytic processes occurs last in the sequence?


What is the role of opsonins?

They create "handles" that make it easier for the pseudopods of phagocytes to attach to the microbe invader.

What is a phagolysosome?

The structure that results from the fusion of a phagosome and a lysosome.


A protein that covers the surface of an invading microbe, making it easier for the phagocyte to ingest.


A vesicle containing only an engulfed invading microorganism.


A vesicle containing only digestive enzymes and other antimicrobial compounds.

How is Streptococcus pneumoniae able to avoid destruction by a phagocyte?

Their capsules make them "slippery" to phagocytes.


They cause the lysosomes to empty their contents into the phagocyte, killing it.


They prevent the fusion of the lysosome and phagosome.

Which microorganism requires the low pH inside a phagolysosome in order to reproduce?

Coxiella burnetii

Which of the following microorganisms use M protein to avoid destruction of a phagocyte?

Streptococcus pyogenes


Haemophilus influenzae


Streptococcus pneumoniae

Phagocytosis is defined as

the ingestion of solid material by a eukaryotic cell.


the ingestion of solid material by a eukaryotic cell.


the feeding of protozoans.


the uptake of liquid material by a eukaryotic cell.

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.

second line of defense

phagocytosis, inflammation, fever, and a variety of antimicrobial substances

Phagocytosis is the process through which

one cell engulfs extracellular material, such as an invading microorganism

Cells that specialize in phagocytosis are referred to as


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

Microfilaments are composed of

protein actin

Polymerization of actin can

lengthen the microfilament

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.

Staphylococcus aureus

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
Myeloperoxidase deficiency
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

Myeloperoxidase deficiency

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

What cellular macromolecules make up the complement pathway?


Based on the animation, which of the following is cleaved by C1?

C2 and C4

Where are the complement proteins found in the body?

The blood serum

Based on the animation, which of the following is responsible for cleaving C3?


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


increase of blood vessel permeability and chemotactic attraction of phagocytes

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