Overview of Adaptive Immune System

Question 1

What is the point of adaptive immune system if innate can get rid of some pathogens?

Answer 1

• In case same (not diff) pathogen comes back so effector cells are ready for potent response
• Latency - prevent reactivation of pathogen that wasn’t fully cleared (latent infection)

Question 2

What are the 2 types of adaptive response?

Answer 2

Learned response (repeated pathogen)
Programmed (detected damage/problem)

Question 3

What things can be recognised causing an adaptive response to take place?

Answer 3

• PAMPs e.g flagellum recognised by TLRs
• Damage detected (DAMPs or CD28 co-stimulation)
• Reoccuring infection e.g. shingles
• Autoimmunity - self vs non self e.g. transplant

Question 4

What are the cells involved in adaptive immunity?

Answer 4

Effector cells called primary lymphocytes

Question 5

What will happen if there are no T cells?

Answer 5

Allows opportunistic infections such as reactivation infections that immune system otherwise would’ve been able to control

Question 6

Give examples of lymphocyte deficiency (of B cells)?

Question 7

Give examples of lymphocyte deficiency (of T cells)?

Question 8

What are all the lymphocytes?

Answer 8

NK cells, B cells and T cells

only B and T are adaptive - have memory

Question 9

What are the different categories to define lymphocytes?

Answer 9

Morphology (small/large nucleus)
Lineage (T or B cells)
Location (tissue resident memory cells or marginal zone B cells)
Differentiation (naiive or memory, immature or mature)
Function (helper, cytotoxic, regulatory)
Phenotype (surface markers e.g. CD4 or CD8)
Specificity (antibody produced or epitope produced according to TCR)
Type of receptor (Ig for B cells, alpha beta or gamma delta in T cells)
Which cytokines they produce (TH1 produces diff types to TH2 cells)

Question 10

What are the 2 main features of adaptive immunity? and why are they important

Answer 10

Specificity
Memory

• allows clonal selection for continued and rapid protection during secondary response

Question 11

What is clonal selection?

Answer 11

One specific type c is clones e.g B cell - produces 1 Ig and T cells produces one T cell receptor (TCR)

Question 12

Where do B cells and T cell originate from?

Answer 12

Bone marrow

Question 13

What does the receptor in B cells look like?

Answer 13

Surface immunoglobulin (B cell receptor) variable region, constant region AND A TRANSMEMBRANE REGION
Antibody has all but transmembrane region

Question 14

What does a T cell receptor have structurally?

Answer 14

Antigen binding site, variable region, constant region, transmembrane region (either alpha and beta chain or gamma and delta chain)

Question 15

What is the structure of an antibody?

Answer 15

Antigen binding site, heavy chain and light chain (only a portion of heavy chain is in constant region) (both in variable region)

Question 16

What do T cell receptors recognise in the antigen binding site?

Answer 16

Peptide sequence (that has been processed and presented) associated to a MHC molecule (in its groove)

Question 17

Where are MHC class 1 molecules found? and what do they present?

Answer 17

On all cells - present intracellular contents

Question 18

What recongises MHC class 1 molecules?

Answer 18

CD8 T cells T cell receptors

Question 19

Where are MHC class 2 molecules found and what do they present?

Answer 19

Found on specialised antigen presenting cells (APC) which have processed and presented peptides

Question 20

Which recognises MHC class 2?

Answer 20

TCR on CD4 T cells

Question 21

What happens in thymic selection briefly? major stages

Answer 21

Positive selection of T cells - must bind to self MHC to select T cells
Negative selection of T cells - Must not bind to self peptides

Question 22

Why is T cells thymic selection important?

Answer 22

Keep balanced amount of correct T cells

Question 23

What happens to T cells after thymic selection?

Answer 23

Naive T cells recirculate (some into peripheral blood and some into lymph nodes)

Question 24

How do we label lymphocytes?

Answer 24

In vivo with deuterium labelled glucose

Question 25

Why are a little amount of naiive T cells found in peripheral blood?

Answer 25

naiive T cells have very slow turnover rates - stay naiive until activated

Question 26

What are the types of memory T cells?

Answer 26

Central memory t cells (TCM)

Effector memory T cells

Question 27

Where are central memory t cells found?

Answer 27

Enter lymph nodes then recirculate

Question 28

Where are effector memory T cells found?

Answer 28

Migrate into tissues for rapid effector activity

Question 29

Which are the types of T cells left after infection (no longer naiive)?

Answer 29

TEM (effector memory cells)
TCM (central memory cells)
Treg (regulatory T cells)

Question 30

What are the steps for B cell repertoire selection?

Answer 30

Positive selection
Receptor editing (to avoid recognising self)
Negative selection
Transition from IgM to IgD mature B cell
Antigen recognition leads to proliferation/differentation e.g. into plasma cells, memory B cells

Question 31

Where are lymphocytes mostly found? and why

Answer 31

not much in blood, more in lymph nodes. as lymph flows through, infected cells detected and correct B/T cell is selected for

Question 32

What is the structure of a lymph nodes

Answer 32

B cells, T cell, macrophages and plasma cells are densely packaged
Lymph flows through vessels with valves to prevent backflow

Question 33

What is the marker of tissue resident T cells?

Answer 33

CD69+ T cells