B Cell And Antibodies

Question 1

What is the primary function of B cells in the immune system?

Answer 1

B cells differentiate into plasma cells that produce antibodies.

Question 2

What type of immunity do antibodies primarily provide?

Answer 2

Humoral immunity.

Question 3

What are the five classes of antibodies?

Answer 3

• IgD
• IgM
• IgG
• IgA
• IgE

Question 4

What is the role of IL-2 in T cell activation?

Answer 4

IL-2 signals the T cell to enter the cell cycle and induces T-cell proliferation.

Question 5

True or False: Activated T cells express a moderate-affinity IL-2 receptor.

Answer 5

False.

Question 6

What are the three signals delivered by APCs to naive T cells?

Answer 6

Co-stimulation, antigen recognition, and cytokine signaling.

Question 7

Define monoclonal antibodies.

Answer 7

Lab produced antibodies specific for a single antigen.

Question 8

What is the complement system?

Answer 8

A complex system of serum proteins that act in a sequence to defend against microorganisms.

Question 9

Fill in the blank: The variable region of an antibody confers __________.

Answer 9

[specificity].

Question 10

What is the main effector mechanism in humoral defense against extracellular microorganisms?

Answer 10

The complement system.

Question 11

What are anaphylatoxins?

Answer 11

C3a and C5a, which activate mast cells and induce inflammation.

Question 12

How do antibodies enhance phagocytosis?

Answer 12

By opsonization through C3b binding to phagocyte receptors.

Question 13

What is the difference between primary and secondary immune responses?

Answer 13

Primary response is the initial contact with an antigen, while secondary response involves memory cells rapidly proliferating upon re-encountering the antigen.

Question 14

What happens during the classical pathway of complement activation?

Answer 14

Antibody binds to antigen, C1 binds to Fc region, and a cascade of complement proteins is activated.

Question 15

Fill in the blank: The __________ pathway of complement activation does not involve antibodies.

Answer 15

[alternative].

Question 16

What is the role of memory B cells?

Answer 16

They remain after an immune response and can quickly proliferate upon re-encountering the same antigen.

Question 17

True or False: Gram-positive bacteria are lysed by complement activation.

Answer 17

False.

Question 18

What are the biological effects of complement cleavage products C3a and C5a?

Answer 18

• Activate mast cells
• Attract phagocytes

Question 19

What is the significance of the a-Gal epitope in xenograft rejection?

Answer 19

Humans produce antibodies against the a-Gal epitope found on animal cells, leading to hyperacute rejection.

Question 20

What happens during the activation of the complement system?

Answer 20

C1 binds to antibodies, cleaves C4, and initiates a cascade leading to formation of the membrane attack complex.

Question 21

What is the role of the hinge region in antibodies?

Answer 21

It allows flexibility for the antibody to bind to widely separated antigens.

Question 22

What is immunological memory?

Answer 22

The ability of memory T and B cells to quickly proliferate and respond to previously encountered antigens.

Question 23

What occurs to antibody titers after the first exposure to an antigen?

Answer 23

There is a steady increase in antibody titer, first IgM then IgG, followed by a decrease.

Question 24

Fill in the blank: The constant region of an antibody is nearly the same in different antibodies and does not associate with __________.

Answer 24

[antigen binding].

Question 25

Name the types of T cells involved in the immune response.

Answer 25

* T Helper cells * Cytotoxic T cells

Question 26

What is the consequence of aging on the immune system?

Answer 26

Increased susceptibility to infectious diseases due to lower levels of immune function.

Question 27

What is the initial contact with an antigen called?

Answer 27

Primary response

Question 28

What happens to memory cells during the secondary response?

Answer 28

They quickly proliferate and produce mostly IgG antibodies

Question 29

What provides the basis for vaccination?

Answer 29

Immunological memory

Question 30

How does aging affect immunity?

Answer 30

Individuals become more susceptible to infectious diseases due to lower levels of immune function

Question 31

What happens to T cells as individuals age?

Answer 31

They become less responsive to antigens and fewer T cells respond to infections

Question 32

What is a potential cause of decreased T cell numbers in older individuals?

Answer 32

Age-related atrophy of the thymus or decreased production of thymic hormones

Question 33

What is the relationship between B cells and aging?

Answer 33

There is a decrease in the number of B cells, leading to slower antibody titre increase

Question 34

Why are vaccinations against influenza provided every year for older individuals?

Answer 34

Due to decreased immune function and lower response to infections

Question 35

Where are immunoglobulins found and what do they bind to?

Answer 35

In extracellular fluids and they bind to antigens

Question 36

What are the three main functions of immunoglobulins?

Answer 36

* Neutralise antigens * Opsinise antigens * Activate complement

Question 37

What do B-lymphocytes differentiate into in response to an antigen?

Answer 37

* Plasma cells * Memory cells

Question 38

What do plasma cells secrete in response to antigen?

Answer 38

Large quantities of immunoglobulin

Question 39

What helps B-lymphocytes to proliferate and differentiate into plasma cells?

Answer 39

Help from a T-lymphocyte specific for the same antigen

Question 40

Where do B-lymphocytes interact with both antigen and T-lymphocytes?

Answer 40

In the secondary lymphoid tissues

Question 41

What forms the antigen binding site of an antibody?

Answer 41

The variable domains of antibody heavy and light chains

Question 42

What must happen to immunoglobulin genes to encode an antibody molecule?

Answer 42

They must recombine