Adaptive Immunity: Receptor Phase

Question 1

Compare Naive and Effector T cells

Answer 1

Naive: T cells that haven’t encountered an antigen

Effector: T cells that have encountered an antigen and can perform functions during an immune response

Question 2

Name 4 types of Antigen-Presenting cells

What kind of T cells do they present to

Answer 2

Dendritic- Naive

Langerhans- Naive

Macrophages- Effector

B cells- Effector

Question 3

What are the 4 key players in adaptive immunity

Answer 3

Naive T cells
Tumour Cells
Pathogen
Antigen-Presenting Cells (APCs)

Question 4

Describe 3 features of APCs

Answer 4

1. Strategic Location;
   - Mucosal membranes (Gut, lung)
   - Skin
   - Blood
   - Lymph nodes and spleen
2. Diversity in pathogen sensors (Intra/ Extracellular)
3. Diversity in pathogen capture mechanisms;
   - Phagocytosis (Whole microbe)
   - Macropinocytosis (Soluble particles)

Question 5

Where are dendritic cells found

Where are B cells found

Answer 5

Dendritic:
Lymph nodes
Blood
Mucous membranes

B cells:
Lymphoid tissues

Question 6

What kinds of immunity combat Intracellular and Extracellular microbes

Answer 6

Humoral immunity- Extracellular microbes

Cell mediated immunity- Intracellular microbes

Question 7

How are pathogens presented to T cells

What genes code for these

Answer 7

• Via Major Histocompatibility Complex (MHC) molecules on the APC Surface
• Human Leukocyte Antigen (HLA) regions

Question 8

Where are MHC Class 1 and Class 2 molecules expressed

Which ones present Intra and Extracellular microbes to T cells
Which T cells are they pretend to to

Answer 8

• MHC Class 1: Expressed on all nucleated cells, Present Intracellular microbes, to CD8+ T cells
• MHC Class 2: Expressed on APCs, Present Extracellular microbes, to CD4+ T cells

Question 9

Outline 2 key features of MHC Molecules

Answer 9

1. Co-dominant expression
   - Both maternal and paternal molecules are co-expressed so increase in no. of different MHC molecules
2. Polymorphic genes
   - Due to different alleles, different individials present different microbes

Question 10

Outline the Endogenous Pathway in 4 steps

Answer 10

1. Viral protein present in cytosol
2. Marked for destruction by proteasome
3. Broken down into Viral peptide and transported to ER by TAP proteins
4. Viral peptide- MHC Class 1 complex formed

Question 11

Outline the Exogenous Pathway in 4 steps

Answer 11

1. Microbes captured
2. Degradation to small peptides
3. Peptide rich vesicles fuse with vesicles containing MHC Class 2 molecules
4. Peptide- MHC Class 2 complex formed

Question 12

Describe 2 features of about the structure of MHC Class 1 AND Class 2 molecules

Answer 12

1. Peptide binding cleft- Variable region with highly polymorphic residues
2. Broad specificity- Many peptides presented by same MHC molecule

Question 13

Describe the clinical importance of MHC molecules in 3 ways

Answer 13

1. Host can combat various microbes
2. No 2 individuals have same set of MHC molecules
3. Different susceptibilities to infections

Question 14

What are 2 clinical problems with MHC molecules

Answer 14

• Major cause for organ transplant rejection

- HLA association with autoimmune disease