Microbiology Module 6

Question 1

List the key attributes of the adaptive immune system

Answer 1

1. Specificity: ability to recognize antigens found of specific pathogens
2. Inductability: The recognition of antigen-containing pathogens induces the cells of the adaptive immune system
3. clonality: one activated, immune cell proliferates and form identical daughter cells
4. unresponsive to self; immune cells do not act on normal body tissues
5. memory: the adaptive immune system responds to repeat infections by the same pathogen faster than it can respond to the initial exposure

Question 2

compare and contrast B and T cells

Answer 2

B cells:
- aka B lymphocytes
-play a major role in the antibody (humoral) immune response
-against all pathogens
T cells:
-aka T lymphocytes
-play a major role in the cell-mediated immune response
-virally infected cells

Question 3

explain how lymph is formed, and its role in the immune system

Answer 3

1. as blood is delivered to the tissues, some plasma exits the capillaries and becomes interstitial fluid
2. Lymphatic capillaries take up interstitial fluid and is the called lymph
3. lymph travels to lymph nodes where it is screened for pathogens and filtered
4. fluid is eventually channeled into veins and returns to circulatory system

Question 4

compare and contrast primary and secondary lymphatic tissue

Answer 4

primary:
-sites of productions and maturation of lymphocytes
-thymus: site of T-cell maturation
-Bone marrow: site of B-cell maturation
secondary:
-sites of lymph filtration
-lymph nodes: serve as filtering and screening centers for lymph before returning it to the bloodstream
-spleen: filters blood rather than lymph
-Mucosa-associated lymphoid tissue (MALT): diffuse system of lymphoid tissue; found in all mucosal linings

Question 5

define antigen and epitope

Answer 5

antigen: specific molecules that the body recognizes as foreign and worthy of attack
epitope: three-dimensional regions on antigens

Question 6

explain the differences between PAMPs and antigens

Answer 6

PAMP is knowing what something is. it is innate.
antigen is using unique features to identify. it is adaptive.

Question 7

compare and contrast auto, endogenous, and exogenous antigens

Answer 7

autoantigens: allow the immune system to recognize itself
exogenous: components of pathogens that are produced by the pathogen itself.
-incudes toxins and other components of microbial cell wells membranes, flagella, and pili
endogenous: produced by microbes that reproduce inside a body’s cells
-end up on the surface of the body’s cells

Question 8

explain the purpose of the major histocompatibility complex proteins

Answer 8

allows the adaptive immune system to respond to both intracellular (endogenous) and extracellular (exogenous) pathogens

Question 9

explain the purpose of MHC1 proteins, the cell where it is found, and the antigens it binds

Answer 9

purpose: provide the “uniform” so your immune system can recognize the body’s cells
found: in the cytoplasm of all nucleated cells
it binds to autoantigens

Question 10

explain the purpose of the MHC2 proteins, the cells where it is found, and the antigens it binds.

Answer 10

purpose: allows APCs to activate the adaptive immune system and mount an immune response against that specific antigen
found: present on antigen-presenting cells (APCs)
antigen presenting cells are phagocytes that present pathogenic antigens on MHC2 proteins.

Question 11

explain the purpose of the cell-mediated immune response

Answer 11

-recognizing the endogenous antigens
-fighting intracellular pathogens

Question 12

describe the shape and function of the regions of the T-cell receptor

Answer 12

Variable region contains the epitope binding site and binds a unique epitope (antigen)

constant region: binds the variable region to the cell

Question 13

compare and contrast the two types of T-cells, what are their functions, how are they differentiated?

Answer 13

-T cytotoxic cells (Tc cells)
-classified as CD8+ T cells
-“workhouse” cells of the cell-mediated immune response
-seek out and destroy endogenous antigens on infected cells
-T Helper cells (Th cells)
-classified as CD4+ T cells (most abundant cells)
-“help” coordinate the adaptive immune response by releasing cytokines and activate other white blood cells
-do not directly seek and destroy invaders
-T helper 1 cells (Th1 cells): initiate the cell-mediated immune response
-T helper 2 cells (Th2 cells): initiate the antibody-mediated immune response

Question 14

explain the purpose of CD proteins. How do they provide cell specificity to T-cells?

Answer 14

-allow the T cell to bind and recognize the MHC protein
-CD8 allows Tc cells bind to MHC1 respond to endogenous antigens
-CD4 allows Th cells bind to antigens presented on APCs

Question 15

describe the infection that the cell-mediate response responds to

Answer 15

-fights intracellular pathogens such as viruses and viral infections
-responds to autogenic cells, such as cancer cells
-

Question 16

How does the innate immune system initiate the cell-mediated immune response?

Question 17

How does the APC find T-cells that recognize the antigens presented on its surface?

Question 18

What is required for the T-helper1 cell to bind to the APC?

Question 19

What is required for the Tc cell to bind to the APC?

Question 20

What role does the Th1 cell play in initiating clonal expansion of Tc cells.

Question 21

What is the purpose of the Memory Cell? Why does it allow for a faster response to a secondary infection?

Answer 21

-allow the body to remember the antigens they have been exposed to in the past
-allow for a faster response since the response time is shorter due to the body having memory of how to fight off the infection

Question 22

Describe how Tc cells would recognize an infected cell

Answer 22

• find infected cells by binding to endogenous antigens though MHC1 and binding to foreign pathogens
  -if there is no foreign pathogen then it is not infected

Question 23

How do Tc cells kill infected cells?

Answer 23

when the patrolling T cytotoxic cell binds to an endogenous antigen, Tc cells release:
-perforins: form pores in the target cell
-granzymes: enter through the pore, break down the host cell proteins, and induce apoptosis
-cytokines: attract phagocytes to the cell

Question 24

Explain the purpose of the Antibody-mediated Immune Response

Answer 24

-bind exogenous antigens
-have antigen-binding site and antigen specificity identical to the BCR of the activated B cell.

Question 25

Describe the shape and function of the regions of the B-cell receptor.

Question 26

Describe the shape and function of antibodies. Relate them to the BCR.

Question 27

Explain the functions of antibodies. How do they improve the immune system?

Question 28

Describe the functions and shapes of each class of antibody.

Question 29

How does class switching result in the transition between antibody classes?

Question 30

Describe the infection that is responded to by the antibody-mediated immune response?

Question 31

How does the innate immune system initiate the antibody-mediated immune response?

Question 32

Explain how a B cells with a BCR that can recognize a pathogen is found by the immune system.

Question 33

Explain how B cells function as an APC, and the role that plays in activating the antibody immune response.

Question 34

Explain how the APC finds and activates a Th2 cell?

Question 35

Explain how the Th2 cell binds and activated the B cell that has bound to the antigen?

Question 36

Explain how the Th2 cell initiates clonal expansion of a B cell.

Question 37

What is the purpose of a plasma cell?

Answer 37

-secrete antibody molecules complementary to the specific antigen bound during activation -> produce and secrete antibodies

Question 38

Describe how HIV is transmitted

Answer 38

-transmitted through blood, semen, pre-seminal fluid, rectal fluids, vaginal fluids, and breast milk
-can be transmitted person to person when these fluids come in contact with a mucous membrane, damaged tissue or are directly injected into the bloodstream
-less common through pregnancy, birth, breastfeeding, or during accidental needle punctures in a healthcare setting

Question 39

List and describe the stages of an HIV infection. What stages have signs and symptoms, which do not? Please explain why?

Explain how HIV impairs the adaptive immune system and eventually leads to AIDs.

Answer 39

acute HIV infection/syndrome:
-occurs 2-4 weeks after virus enters bloodstream
-HIV infects helper T cells and the body mounts an immune response
-symptoms resolve after a few weeks -> virus in the blood can still be detected -> still infected

clinical latency (HIV inactivity or dormancy)
-HIV is still active but reproduces at low levels -> no apparent symptoms
-can last from months to years -> people who take medicine are in this stage longer than those who don’t
-untreated individuals are contagious during this stage while treated individuals are not

acquired immunodeficiency syndrome (AIDS)
-diagnosed when T helper cells levels are below 200 cells/mm3
-increasing number of severe illnesses due to limited immune system
-typically survive about 3 years
-individuals w/ aids have high viral loads and are therefore highly contagious

Question 40

Explain how an HIV infection leads to an increase in opportunistic infections.

Answer 40

since HIV causes a persistent infection and constantly attacks the immune system, the immune system is down. This causes other acute infections to be able to attack the body since there is no strong immune system to protect it.

Question 41

Describe how HIV is treated, prevented, and diagnosed.

Answer 41

diagnosis:
-through a blood test
-measures the amount of HIV specific antibodies present in blood

treatment:
-antiretroviral therapies (ART)
-3 or more drugs in combination
-2 reverse transcriptase inhibitors -> specific to HIV
-third drug can be a protease inhibitor, integrase inhibitor or reverse transcriptase inhibitor

prevention:
-prevented through the use of condoms during intercourse
-drug methods
-Pre-exposure prophylaxis
-post-exposure prophylaxis
-no current vaccine

Question 42

Explain the purpose of Clonal Deletion.

Question 43

Explain why the secondary immune response does not prevent contamination or infections, but diseases?

Answer 43

the secondary immune response does not prevent contamination or infections but only diseases through the usage of memory cells. Memory cells shorten the immune response time, causing there to be more IgG which in result kills pathogens before signs and symptoms can occur. However, individuals can still have brief infections or by asymptomatic.

Question 44

Compare and contrast the primary and secondary immune responses.

Answer 44

primary immune response:
-adaptive immune system must be induced
-takes time to mount an effective response and form memory
-little IgG produced during primary response

secondary immune response:
-triggers a memory response by activating memory cells
-do not require Th cell signaling to initiate clone expansion
-much faster immune response -> lots of IgG
-pathogens can cause a brief infection
-individuals can be asymptomatic

Question 45

Define Active Immunization

Answer 45

-allow the body to be safely exposed to the antigens on a pathogen and form a memory

Question 46

Define Passive Immunotherapy

Answer 46

-protect the body from current infection, limiting damage

Question 47

Compare and contrast active Immunization and passive immunotherapy

Answer 47

-active:
-artificial solution -> injection of antigen
-allow the body to be safely exposed to the antigens on a pathogen and form a memory
-when exposed to pathogen, body can respond with a secondary response

-passive:
-injection of antibodies -> goal of adaptive activation
-no memory
-can be passed naturally from person to person
-immediate protection

Question 48

List each of the methods by which a vaccine can introduces a memory. Explain the positives and negatives of each method.

Answer 48

-attenuated (modified live) vaccines: process of reducing virulence
-benefits
-active microbes stimulate a strong immune response that is accompanied by long-lived memory
-can provide contact immunity
-drawbacks
-modified microbes may retain enough residual virulence to cause disease in susceptible individuals
-possible mutation to an infectious form
-must be refrigerated

-Inactivated Vaccines:
-whole inactivated vaccines: inactivated (killed) whole microbes
-subunit vaccines: antigenic fragments
-toxoid vaccines: inactivated toxins
-benefits:
-Safe for immunocompromised patients
-stable at room temp.
-drawbacks
-each exposure produces less memory -> booster required

Question 49

Explain the purpose of a booster shot. What vaccine methods typically require boosters.

Answer 49

-boosters are additional vaccine injections with the goal of increasing the memory cell number
-more exposure (booster shots) -> more memory -> better and faster response
-toxoid and inactivated vaccines typically require boosters due to them producing less memory cells and are at a greater risk of losing immunity over time

Question 50

Describe what is measured when an antibody titer is taken. How does it provide information on a person’s immunity?