module 01 section 03 (adaptive immune system)

Question 1

what are the 6 unique features of the adaptive IS?

Answer 1

(1) discrimination
(2) diversity
(3) specificity
(4) specialization
(5) memory
(6) self-limitation

Question 2

define “discrimination” w respect to the adaptive IS

Answer 2

the ability of the adaptive IS to discriminate btwn self and non-self prevents injury to the host during response to pathogens

Question 3

define “diversity” w respect to the adaptive IS

Answer 3

the adaptive IS responds to a wide variety of microbes and molecules

Question 4

define “specificity” w respect to the adaptive IS

Answer 4

the adaptive IS is capable of distinguishing subtle differences amongst foreign antigens

Question 5

define “specialization” w respect to the adaptive IS

Answer 5

• the immune response generated is antigen-dependent, ensuring optimal defense against each type of microbe
• as mature cells need time to be activates there is a lag period in response time of 4-5 days

Question 6

define “memory” w respect to the adaptive IS

Answer 6

the adaptive IS has enhanced responses to a microbe following repeated exposures (I.e. it has an immunological memory)

Question 7

define “self-limitation” w respect to the adaptive IS

Answer 7

cells of the adaptive IS allow microbe-activated immune responses to return to their basal state (allowing for homeostasis)

Question 8

list the cells of the adaptive IS

Answer 8

B and T lymphocytes

Question 9

describe T cell activation

Answer 9

• to elicit an adaptive immune response, t-cells require activation by professional antigen-presenting cells (APCs)
• APCs have the ability to present processed antigens through major histocompatibility complex molecules (this will be covered later)

Question 10

how are T-cells distinguished from other lymphocytes?

Answer 10

by the presence of the T-cell receptor on the cell surface

Question 11

describe the funtion of T-cells in terms of immunity

list the types of T-cells

Answer 11

• T-cells are important for both cell mediated and humoral immunity
• all T-cells recognize the processed antigen in complex with the major histocompatibility complex molecules, via the T-cell receptor
• Naive T-cells can develop into helper T-cells or cytotoxic T-cells

Question 12

list and define the two types of adaptive immunity

Answer 12

(1) cell mediated: any adaptive immune response in which antigen specific t-cells have the main role
- i.e. focused on the adaptive immune response to antigens expressed in/on cells
(2) humoral immunity: the antibody-specific mediated immunity made in a humoral immune response (mediated by substances found in the bodily fluids, e.g. secreted antibodies)
- i.e. focused on the adaptive immune response to antigens found circulating freely

Question 13

what are the helper T-cell co-receptors?

what is the function of these cells?

Answer 13

• express CD4 co-receptors
• these are the regulatory cells (have a role in maintaining or supressing immune cells/reactions)
• are also involved in antibody production

Question 14

what are the cytotoxic T-cell co-receptors?

what is the function of these cells?

Answer 14

• express CD8 co-receptors
• these are the effector cells (short-lived, activated cells that respond to a stimulus and effect change)
• i.e., are involved in killing of target cells, such as virally infected cells

Question 15

where do T-cells originate?

Answer 15

like all immune cells, T-cells origionate from the hematopoietic stem cells in the bone marrow

Question 16

explain (generally) the process of T-cell maturation

Answer 16

• progenitor T-cells propagate and undergo differentiation in the thymus medullary and cortex
• naive T-cells (which express neither CD4 or CD8) develop from double negative cells into double positive cells (briefly expressing both CD4 and CD8 receptors)
• then they differentiate into mature T-cells, expressing the T-cell receptor with either CD4 or CD8 (i.e. are now single positive receptors)

Question 17

what does T-cell maturation rely on?

Answer 17

the development of the T-cell receptor

Question 18

explain in detail the types of helper T-cells and their corresponding functions

Answer 18

(1) Th1: activate macrophages and are responsible for cell-mediated immunity
(2) Th2: induce mature B-cells to differentiate into plasma B-cells to produce antibodies (which are responsible for humoral immunity)

Question 19

how are B-cells distinguished from other lymphocytes?

Answer 19

by the presence of the B-cell receptor on the cell surface

Question 20

describe the function of B-cells in terms of immunity

Answer 20

• humoral (antibody-mediated) immunity consists of B-cells
• these are responsible for secreting or expressing antibodies on their surface
• B-cells also express other characteristic surface markers including B7 (regulatory molecule) and CD40 (molecule critical for antigen-stimulated B-cell survival)

Question 21

where do B-cells origionate?

Answer 21

like all immune cells, B-cells origionate from the hematopoietic stem cells in the bone marrow

Question 22

explain the process of B-cell maturation

Answer 22

occurs in many stages in the bone marrow, each defined by a unique gene expression pattern

Question 23

list and define the main classes of B-cells

Answer 23

(1) immature B-cell: express cell-surface immunoglobulin (Ig) M
(2) mature B-cell: express both cell-surface IgM and IgD

Question 24

list and define the main subclasses of mature B-cells

Answer 24

(1) plasma B-cells: secrete antibodies following antigen stimulation
- these circulate plasma and lymph as a part of humoral immunity
(2) memory B-cells: involved I secondary antibody response; a fundamental principle in vaccination

Question 25

define “antibodies”

how many classes are there? list them.

Answer 25

• aka immunoglobulins (Ig)
• Y-shaped proteins used by the immune system to neutralize foreign antigens
• there are 5 classes: IgA, IgD, IgE, IgG, IgM

Question 26

where is IgA found and what is its role?

Answer 26

• found in high concentrations in mucous membranes such as respiratory passages, GI tract, saliva, tears
• acts primarily as a neutralizing antibody to prevent the attachment of pathogens to muscosal epithelial cells
• responsible for the antimicrobial activity in secretions

Question 27

where is IgD found and what is its role?

Answer 27

• exist in small amounts in the blood
• has no known biological effects
• expressed on the cell surface together with IgM on mature B-cells that have not been exposed to antigens

Question 28

where is IgE found and what is its role?

Answer 28

• found in the lungs, skin and mucous membranes
• plays a role in anaphylaxis through the release of histamine from granulocytes (following exposure to allergens)
• protects against parasitic infection

Question 29

where is IgG found and what is its role?

Answer 29

• found in all bodily fluids fighting bacterial and viral infections
• its the only antibody that can pass throught the placenta to provide immunity to the fetus

Question 30

where is IgM found and what is its role?

Answer 30

• largest antibody
• found mainly in the blood and lymph fluid
• this is the first antibody to be made by the body to fight a microbial infection
• also an excellent complement activator