9- Immune system 2

Question 1

What is an antigen? 3 examples?

Answer 1

Anything the body considers to be foreign
bacteria
fungi
viruses

Question 2

Where does the name antigen come from?

Answer 2

antibody generator

Question 3

antigens that enter the bloodstream get deposited where?

Answer 3

spleen

Question 4

antigens that enter the skin get deposited where?

Answer 4

lymph nodes

Question 5

antigens that penetrate mucous membranes get deposited where?

Answer 5

mucosa associated lymphoid tissue​

Question 6

What is an epitope?

Answer 6

The epitope is considered the antigenic determinant (allows recognition) - it triggers​ the immune response

Question 7

A smaller substance on an antigen that possesses reactivity but lacks immunogenicity?

Answer 7

A hapten (needs to be attached to a carrier protein)

Question 8

Where are antigen receptors present?

Answer 8

On the plasma membranes of lymphocytes

Question 9

What are Major Histocompatibility ​Complex Antigens​ (MHC Antigens)?

Answer 9

(MHC Antigens) are ‘self’ antigens and act as surface markers that define our cells from foreign cells.

In humans they are called Human Leukocyte Antigens (HLA)

Question 10

MHC-I antigens are in which cell membranes?

Answer 10

All except RBCs

Question 11

Where are MHC-II antigens present?

Answer 11

MHC-II antigens appear only on the cell membrane of Antigen Presenting Cells (dendritic cells, macrophages, B cells)

Question 12

3 antigen-presenting cells?

Answer 12

Dendritic cells
Macrophages
B cells

Question 13

Where do B cells bind to antigens?

Answer 13

B cells can bind to antigens in lymph, interstitial fluid, or blood plasma

Question 14

When do Helper T cells “see” antigens?

Answer 14

Helper T cells “see” antigens if part of MHC-II molecules on surface of antigen presenting cell​

Question 15

When do Cytotoxic T cells “see” antigens?

Answer 15

Cytotoxic T cells “see” antigens if part of MHC-I molecules on surface of body cells​

Question 16

Where are exogenous located?

Answer 16

outside the body’s cells

Question 17

An example of an antigen presenting cell?

Answer 17

macrophage

presents fragments of antigen for recognition

Question 18

Where are endogenous located?

Answer 18

Inside the body’s cells

they include viral proteins or proteins produced by cancer cells

Question 19

What are cytokines?

Answer 19

small protein hormones secreted by lymphocytes and antigen-presenting cells, fibroblasts, endothelial cells, monocytes, hepatocytes, and kidney cells

they ‘co-stimulate’ B and T cell responses

Question 20

What does cell-mediated immunity affect

Answer 20

cell vs cell

Question 21

2 types of T cells?

Answer 21

Helper T cells

Cytotoxic T cells

Question 22

what do helper T cells do?

Answer 22

• Help B cells produce antibodies
• Aid phagocytes in ingesting microbes
• Help activate the other type of T cell– cytotoxic T cells

Question 23

how do T cells and cytotoxic cells become activated?

Answer 23

antigen recognition

co-stimulation (Interleukin-2)

Question 24

What do active helper T cells do?

Answer 24

secrete cytokines including interleukin-2 (IL-2)

Question 25

Interleukin-2 (IL-2) enhances activation and proliferation of which cells?

Answer 25

B cells, T cells and Natural Killer cells

Question 26

what does a clonal section of an activated T cell produce?

Answer 26

• active helper T cells

- memory helper T cells

Question 27

what do cytotoxic cells do?

Answer 27

kill the cell that caused an immune response

Question 28

4 steps for cytotoxic T cells to kill their target cell?

Answer 28

1- Releasing Granzymes
(protein-digesting enzymes that trigger apoptosis)

2- Releasing proteins
(perforin and granulysin)

3- Secreting Lymphotoxin
(activates enzymes in target cell causing its DNA to fragment​)

4- Secrete gamma-interferon to activate phagocytic cells​

Question 29

5 principle classes of antibodies?

Answer 29

IgG, IgA, IgM, IgD, and IgE​.

Question 30

What does Antibody-mediated (humoral) immunity (AMI) refer to?

Answer 30

the destruction of antigens by antibodies in extracellular fluid

Question 31

describe what happens in antibody-mediated immunity (AMI)

Answer 31

• B cells transform into plasma cells, ​

- Plasma cells synthesize and secrete specific proteins called antibodies ​

Question 32

the three major steps in the antibody-mediated immune response are?

Answer 32

1- Activation of B cells​
2- Clonal selection and Antibody secretion​
3- Antigen-antibody complex formation​

Question 33

4 steps in activation of B cells

Answer 33

1- stimulation
(activated when an antigen is presented)

2- antigen binding

3- antigen processing
(antigen is taken into the B cell, broken down into peptide fragments and combined with the MHC-II self-antigen, and moved to the B cell surface)

4- co-stimulation
(Helper T cells recognize the antigen-MHC-II combination and produce interleukin-2 and other cytokines that function as co-stimulators to activate B cells)

Question 34

5 functions of antibodies?

Answer 34

1- neutralise antigens (block toxins and attachment)

2- immobilise bacteria (attack cilia/flagella)

3- agglutinate and precipitate antigens
(cross-linking to clump them)

4- complement activation
(Antigen–antibody complexes initiate complement system)

5- enhancing phagocytosis

Question 35

what is the complement system?

Answer 35

a defensive system made up of over 30 inactive proteins (produced by the liver) and found circulating in blood plasma and within tissues

enhances phagocytosis, inflammation and cell lysis

Question 36

Define self-recognition and self-tolerance

Answer 36

Self-recognition: T cells’ ability to recognise self major histocompatibility complex (MHC) proteins.​

Self-tolerance: T cells lacking reactivity to peptide fragments from self proteins.​​

Question 37

4 basic types of hypersensitivity reactions?

Answer 37

Type I (anaphylaxis) reactions​
Type II (cytotoxic) reactions​
Type III (immune complex) reactions​
Type IV (cell-mediated) reactions or delayed hypersensitivity reactions​