Adaptive Immune Response to Intracellular and Extracellular pathogens

Question 1

Cells associated with the innate immune response have an important role in the

Answer 1

early phase of infection.

Question 2

Activation of NK cells leads to

Answer 2

degranulation: the degranulation kills the infected cell

Question 3

Antigen specific cytotoxic T cells (i.e., CD8+ T cells) are involved with

Answer 3

eradicating intracellular pathogens

Question 4

Naïve T cells come into contact with APC in

Answer 4

lymph nodes. Interactions with APC are necessary to activate the T cells.

Question 5

CD4+ T Cells can Provide Co-stimulation to Activate

Answer 5

CD8+ T Cells

Professional APC’s phagocytose microbe infected cell (often apoptotic)
Microbial antigen is presented in context of MHCI and/or MHCII
CD4+ helper T cells provide co-stimulation needed for activation of naïve CD8+ T cells

Question 6

CD4+ T Cells Help APC Activate

Answer 6

CD8+ T Cells

Professional APC’s phagocytose microbe infected cell (often apoptotic)
Microbial antigen is presented in context of MHCII
CD40L on the CD4+ T cell binds to CD40, which increases the ability of the APC to present Ag and activate CD8+ T cells.

Question 7

Upon activation, naïve CD8+ T cells “differentiate” into

Answer 7

cytotoxic T lymphocytes (CTL).

Develop membrane bound granules that contain perforin and granzyme
Ability to secrete cytokines, such as IFN-γ and TNF-α

Question 8

Activated T cells (now referred to as CTLs) must migrate to site of infection and be retained so that they can express their

Answer 8

effector functions and eradicate microbe- infected cells

Question 9

CTLs kill targets that express the same

Answer 9

class I-associated antigen that triggered the proliferation and differentiation of naïve CD8+ T cells to become CTLs
MHCI/peptide complex
Accessory molecules: CD8 and LFA-1

Question 10

Two important components of the granule,

Answer 10

perforin and granzyme.

Question 11

Perforin helps

Answer 11

granzyme get into the cell.

Question 12

Granzyme induces

Answer 12

apoptosis in the target cell by activating apoptotic pathways.

Question 13

How do Fas:FasL interactions eradicate cells infected with an intracellular pathogen?

Answer 13

FasL will activate Fas on a microbe infected cell.

Fas will activate apoptotic pathways in the infected cell.

Question 14

Are CD4+ T Cells Important?

Answer 14

1. They produce IFN-γ to activate Macrophages

Question 15

Are CD4+ T Cells Important?

Answer 15

2. They produce cytokines to provide co-stimulation for CD8+ T cell activation
3. They produce cytokines to enhance the activity of APC’s.

Question 16

Some T cells will be retained as

Answer 16

long-lived memory cells.

Question 17

The Humoral Immune Response Involves

Answer 17

Antibody Production

Question 18

B Lymphocytes Produce

Answer 18

Antibodies

Question 19

But, in order for B cells to produce antibody, they must become

Answer 19

activated. Naïve B cells can NOT produce antibodies.

Question 20

Soluble antigen is also capable of

Answer 20

activating B cells

Involves crosslinking of immunoglobulin receptor (primarily IgM)
Typically involves antigens with long repeating epitopes (e.g., LPS), but not proteins
Primarily results in the production of IgM

Question 21

Isotype (i.e., Class) Switching is Dependent Upon

Answer 21

Interactions with T Cells And Cytokines

Question 22

What is the most prevalent antibody isotype in the mouth?

Answer 22

IgA

Question 23

IgA Must be Secreted Onto

Answer 23

Mucosal Surfaces

Question 24

Long lived antibody producing plasma cells and memory B cells take up residence in

Answer 24

bone marrow and secondary lymph nodes (respectively)

Question 25

Antibodies can opsonize

Answer 25

microbes to facilitate phagocytosis.

Question 26

Active immunization is know as vaccination.

Answer 26

It induces adaptive immunity, immunological memory and protection.
It involves “live” or killed (inactivated) vaccines.
A wide range of antigenic preparations are in use.

Question 27

Passive immunization is accomplished by the

Answer 27

passive injection of preformed antibodies.

Question 28

Live attenuated organisms - Organisms whose virulence has been

Answer 28

artificially reduced. Replication of the vaccine strain in the host reproduces many of the features of wild type infection, without causing clinical disease. Most successful viral vaccines belong to this group.

Question 29

2. Heterologous vaccines

Answer 29

• Closely related organism of lesser virulence, which shares many antigens with the virulent organism. Both cowpox virus and vaccinia virus are closely related to variola virus, the causative agent of smallpox. Widespread use of vaccinia virus as a vaccine has lead to the world-wide eradication of smallpox.

Question 30

3. Live recombinant vaccines –

Answer 30

Using genetic engineering, a gene coding for an immunogenic protein from one organism is placed in the genome of another (such as vaccinia virus). The organism expressing a foreign gene is called a recombinant.

Question 31

3. Live recombinant vaccines –

Answer 31

Using genetic engineering, a gene coding for an immunogenic protein from one organism is placed in the genome of another (such as vaccinia virus). The organism expressing a foreign gene is called a recombinant.

Question 32

Attributes - live vaccines

Answer 32

Good immune response – induces CMI and antibody, and immunity is long lived. Usually a single dose is all that is required.
Safety - Danger of reversion to virulence. Can’t be used in immunocomprised patients.
Stability - Organisms in the vaccine must remain viable in order to infect and replicate in the host. Sensitive to storage conditions. Maintenance of the cold chain is very important.
Expense – Inexpensive to prepare
Potential drawbacks to these vaccines include: the danger of reversion to virulence and the possibility of causing extensive disease in immunocompromised individuals.

Question 33

Killed (inactivated) vaccines

Answer 33

Killed vaccines are made when safe live vaccines have not been developed or when reversion to the wild type is common. The organism inactivated with either beta-propiolactone or formaldehyde. These vaccines are not infectious and are therefore relatively safe.
Subcellular fractions - It may be possible to use a purified preparation of a microbial protein as a vaccine. The protein is purified from the culture suspension. These vaccines are safe and fewer local reactions occur at the injection site.
Recombinant proteins - Immunogenic proteins of virulent organisms may be synthesized artificially by introducing the gene coding for the protein into an expression vector, such as E-coli or yeasts. The protein can be extracted from lysates of the expression vector, then concentrated and purified for use as a vaccine. The only example in current use is the hepatitis B vaccine.

Question 34

Attributes - Killed vaccines

Answer 34

Immune response
poor; primarily an antibody response
- little cell mediated immunity.
response is short-lived and multiple doses are needed.
may be enhanced by the incorporation of adjuvants into vaccine
1. Safety
Inactivated, therefore cannot replicate in the host and cause disease.
Local reactions at the site of injection may occur.
2. Stability
Efficacy of the vaccine does not rely on the viability of the organisms.
These vaccines tend to withstand more adverse storage conditions.
3. Expense
Expensive to prepare.