6. Immunity with memory Part 2

Question 1

List the 4 ways in which antibodies act:

Answer 1

• Neutralisation
• Sticking particulate antigens together
• Opsonisation
• Activation of complement

Question 2

What is neutralisation?

Answer 2

Antibodies bind to viral binding sites or coat bacterial toxins so that particles cannot bind to the host cell (cannot enter in the case of viruses) and limits mobility.

Question 3

Describe how antibodies stick particulate antigens together:

Answer 3

Foreign organisms are clumped together (agglutination), which enhances phagocytosis.

Question 4

What is opsonisation?

Answer 4

Antibodies stuck to an antigen target it for destruction and make it easier for phagocytes to find the antibody, and enhances phagocytosis.

Question 5

Describe the 2 ways antibodies activate complements

Answer 5

1. Presence of a pathogen (non-specific)
2. Antibody-antigen interactions (specific)
   • Proteins form a pore in cell membrane, resulting in cell rupture (lysis)
   • Enhances phagocytosis
   • Enhances inflammation

Question 6

List 4 advantages of the humoral response:

Answer 6

• Plasma cells take care of the immediate infection (antibodies typically persist for about 28 days)
• Memory cells stay dormant in the body for months or years holding antibodies on their plasma membrane, waiting for an antigen to bind
• If months later a second exposure occurs B memory cells rapidly dived and differentiate into plasma cells
• The response is much faster than initially (more memory B cells present than the original naïve B cell pool) and often attack disease before symptoms occur

Question 7

Describe the cell-mediated response:

Answer 7

• Involves directly killing virally infected and cancerous cells by Tc lymphocytes
• Distinguish self from non-self by membrane-bound cell receptors
• Do not bind antigens directly but instead recognise MHC Class I signals to identify targets
• Release powerful cytotoxins when they encounter a target cell

Question 8

How are memory T cells formed and what is their function?

Answer 8

When T cells bind to an antigen and are activated by T helper cells, they rapidly divide and differentiate into memory T cells and effector cells.

Question 9

What are the antigen recognition abilities of B cells?

Answer 9

Recognise antigens that are not present in MHC.

Question 10

What are the antigen recognition abilities of helper T cells?

Answer 10

Recognise antigens in MHCII.

Question 11

What are the antigen recognition abilities of T cells?

Answer 11

Recognise antigens in MHCI.

Question 12

Why does the body jump straight to level 3 responses (adaptive/specific immune response)?

Answer 12

Innate response is to initially protect and manage the disease until the specific weapons can be developed

Question 13

What are vaccines and why are adjuvants usually added to them?

Answer 13

Are dead or non-infectious versions of a disease (or even antigens found on the surface of the disease) that allow the lymphocytes to develop into memory cells.
-Substances call adjuvants are usually added to vaccines to activate the innate system to ensure the level three defences are activated

Question 14

What is herd immunity?

Answer 14

If a significant proportion of a population is immunised against a disease, even if the disease is introduced, it can’t spread through that population.

Question 15

Describe active acquired immunity:

Answer 15

-Results in memory B cells and T cells
Types:
-Natural (Antibodies and memory B cells after exposure to infection)
-Induced/artificial (Antibodies made after injection or ingestion of vaccine)

Question 16

Describe passive acquired immunity:

Answer 16

-No memory cells
Types:
-Natural (Antibodies acquired by baby across the placenta or in mother’s milk)
-Induced/artificial (Antibodies acquired through injection of immunoglobulins (antibodies))

Question 17

What are monoclonal antibodies?

Answer 17

Cultured B cells made in labs, which can be used if only one particular type of antibody is needed.

• B cells are fused with cells extracted from a plasma cell tumour to create a hybridoma
• Cells will continually reproduce indefinitely and produce antibodies of the same type

Question 18

What is an allergy? Give some examples of its symptoms

Answer 18

An exaggerated immune response that results in tissue damage when in contact with an allergen.
-Sneezing, itchiness and inflammation, skin irritation, swelling, mucus production

Question 19

What is an allergen?

Answer 19

Substance (dust, pollen) that causes an immune response without an infectious agent.

Question 20

What is histamine?

Answer 20

A chemical released by mast cells and basophils that increases blood flow and the permeability of capillaries.

Question 21

Give 3 examples of allergy treatments:

Answer 21

Antihistamines or cortisone, which suppresses the immune system, or immunotherapy

Question 22

Describe immunotherapy:

Answer 22

• Uses the injection of very small amounts of the allergen, increasing IgG production
• High IgG levels in the body mean IgG will likely bind to the allergen before IgE so mast cells will not be activated

Question 23

Describe how autoimmunity could occur:

Answer 23

• If self-attacking T cells fail to be destroyed during the normal process, the body can attack its own cells
• Our immune system can respond to self as if is non-self
• Almost any part if the body can be affected but most commonly involves acting on skin, kidneys, and joints

Question 24

Describe mutliple sclerosis as an example of an autoimmune disease:

Answer 24

Oligodendrocytes that form myelin sheath are attacked and destroyed

• This impairs transmission of action potentials along axon
• TH mistakenly recognise components of myelin as foreign and are activated
• If blood-brain barrier is damage (Eg. Due to infection) TH and other lymphocytes can enter central nervous system and start destroying myelin
• As myelin is destroyed, macrophages and dendritic cells activated by TH, present more auto-antigens and response increases

Question 25

Treatments for MS are designed to…

Answer 25

1. Block the action of cytokines (B and T cell activation)
2. Prevent lymphocyte entry into CNS
   - By keeping them in lymph nodes
   - By preventing migration from circulation through blood brain barrier
3. New drugs in development take new knowledge of signalling molecules to either activate pathways or block pathways
   - Monoclonal antibodies bind and neutralise cytokines
   - Decoy receptors to prevent cytokines binding ‘real’ receptors

Question 26

Describe HIV as an example of an immunodeficient disease:

Answer 26

• Targets TH cells by binding to specific receptors and injecting RNA
• Stimulated to produce more HIV viruses that bud from most cell plasma membrane to infect other cells until that TH cell is killed
• As infection progresses, the body loses the ability to fight back against the virus as more TH cells are killed
• If untreated the infected individual becomes prone to multiple infections from pathogens that would be relatively harmless under normal conditions

Question 27

How do treatments for HIV work, and how does the disease spread?

Answer 27

• Drugs are designed to block the spread of the virus in the host such as replication, binding to the receptors ect.
• Spread by sharing fluids (Eg. Needles, sexual contact, from mother to child during pregnancy and birth)