S7 Adaptive Immune System Part 2

Question 1

When do antigen presenting cells mature?

Answer 1

When they ‘capture’ an antigen

Question 2

Where in lymphoid tissue do T cells become activated, B cells become activated and where do they meet?

Answer 2

• parafollicular cortex (T cell zone)
• lymphoid follicle (B cell zone)
• edge of follicle

Question 3

Where are B and T lymphocytes produced? Where do they mature?

Answer 3

Produced in bone marrow

T cells - mature in thymus
B cells - mature in tissues following contact with the antigen

Question 4

Where do B and T lymphocytes accumulate?

Answer 4

In lymphoid tissues e.g. MALT, lymph nodes and spleen

Question 5

What are the main 3 lymph nodes?

Answer 5

• cervical (neck)
• axillary (armpit)
• spleen (inguinal)

Question 6

What is lymphadenopathy?

Answer 6

Swelling that occurs in lymph nodes/tissues/etc when B and T cells are activated by the antigen and start proliferating

Question 7

How are antigens recognised by T lymphocytes?

Answer 7

Antigens are recognised by T cell receptors (TCR)

• CD4+ T cells recognise peptides presented by MHC class II molecules
• CD8+ T cells recognise peptides presented by MHC class I molecules

Question 8

What is a T cell receptor (TCR) like?

Answer 8

• alpha and beta chains (variable region)
• CD3 complex
• accessory molecules - CD4 or CD8

Question 9

How are T lymphocytes activated?

Answer 9

By co-stimulation

* a co-stimulatory protein is needed to fully activate a T cell

Question 10

What activates CD4+ T cells to produce the different variants?

Answer 10

Activated by chemical mediator e.g. IL-12/4/1/6/10 or TGF-beta

Question 11

What do TH1 CD4+ T cells cause stimulated by IL-12?

Answer 11

• CD8+ T cells to differentiate
• macrophage recruitment and activation
• stimulates B cells to produce IgG or IgA

This is cell mediated immunity (against extracellular pathogens - bacteria, viruses, fungi)

Question 12

What do TH2 CD4+ T cells cause stimulated by IL-4?

Answer 12

• stimulate B cells to produce IgE
• activate eosinophils to kill pathogens
• activates mast cells against allergies

This is humoral immunity (against extracellular pathogens - parasites, worms)

Question 13

What do TH17 CD4+ T cells cause stimulated by IL-1/6?

Answer 13

• recruitment and activation of neutrophils

Question 14

What do THreg CD4+ T cells cause stimulated by IL-10/TGF-beta?

Answer 14

• tolerance

* immune suppression

Question 15

What is required to activate effector CD8+ T cells?

Answer 15

TH1 (for activation of effector CD8+ T cells from naive CD8+ T cells)

Question 16

If an unaffected cell has MHC I molecules presenting self-antigens will this be detected by cytotoxic lymphocytes?

Answer 16

No

Question 17

How are antigens recognised by B lymphocytes?

Answer 17

By B cell receptors (BCR) which are membrane bound antibodies and are unique and specific for each cell

Question 18

What types of antigen to B lymphocytes recognise?

Answer 18

• macromolecules (proteins, polysaccharides, lipids, nucleic acids)
• small chemicals

Question 19

What is required for activation of B lymphocytes?

Answer 19

Multiple signals

1. BCR engagement - signal transduction
2. TCR engagement - this is antigen specific
3. Cytokine release

Question 20

Why do you need T helper cells involved in B lymphocyte activation?

Answer 20

If didn’t have T helper cells, would only be able to produce IgM antibodies, T helper cells are involved in the switching of antibody production to e.g. IgG due to the CD40L on T cells

Question 21

Production of which antibodies is thymus-dependent?

Answer 21

IgG, IgE and IgA

Question 22

Why do we have booster vaccinations?

Answer 22

To increase the amount of IgG (better protection than IgM) - in secondary response

Question 23

How can you tell if exposure to an infection is acute of chronic?

Answer 23

By the type of antibody present

• acute - more IgM
• chronic - more IgG

Question 24

What is the role of antibody IgA?

Answer 24

Involved in mucosal immunity e.g. GI tract and respiratory tract immunity

Question 25

What is the role of antibody IgM?

Answer 25

Complement antibody

This is the first antibody produced

Question 26

What is the role of antibody IgE?

Answer 26

Immunity against helminths and allergies

Question 27

What should you consider/assess when looking for signs of an adaptive immune response?

Answer 27

• portal of entry
• is there a fever?
• any acute phase reactions e.g. CRP
• neutrophil number?
• phagocyte function?
• lymphadenopathy
• lymphocyte number and function serology

Question 28

What medical achievements have been derived from studying the adaptive immune response?

Answer 28

• disease prevention - vaccines
• immunoglobulin therapies for those with immune deficiencies
• immediate protection - antibody transfer (passive immunisation) e.g. for rabies
• diagnostic tests (antibody based) - for infectious diseases, autoimmune diseases and blood type and HLA types

Question 29

DiGeorge syndrome is an immune deficiency resulting from an impaired thymic development. Which immune components will be affected in these patients?

Answer 29

T cell and B cell function

Need T cells to fully activate B cells

Question 30

What is the type of CD4+ T cells that respond to intracellular pathogens by recruiting and activating phagocytic cells?

Answer 30

TH1

Question 31

If a patient doesn’t have CD40L on their T cells (due to a mutation), what antibody will they most likely produce in response to Staphylococcus aureus?

Answer 31

IgM

Question 32

Which MHC molecule expresses the viral peptides of varicella zoster virus?

Answer 32

MHC I

Question 33

How would you check if someone has had chickenpox before?

Answer 33

Serology for varicella zoster virus antibodies (IgG)

Question 34

Which factors from the adaptive immunity will be used against the virus?

Answer 34

CD8+ T cells (cytotoxic T cells)

Activated by TH1 cells