Adaptive Immunity

Question 1

Features of adaptive immunity

Answer 1

Requires antigen
Retains memory
Involves dendritic cells and lymphocytes

Question 2

Function of dendritic cell

Answer 2

• Capture material in tissue, process this material and take it to peripheral lymphoid organs
• Carry out antigen presentation to T cells and causes production of first signal when binding with complementary TCR
• Dendritic cell also produces second signal for T cell activation

Question 3

Antigen presentation to T-cells

Answer 3

• T-cells never binds to antigen in their native configuration
• TCR bind to peptide from foreign protein that are presented by MHC molecule

Question 4

Important features of MHC

Answer 4

• MHC molecules are highly polymorphic
• MHC 1 has a transmembrane alpha peptide and a beta microglobulin
• MHC 2 has transmembrane alpha and beta peptide
• MHC 1 presents intracellular proteins to CD8 T cells
• MHC 2 presents extracellular proteins to CD4 cytotoxic T cells

Question 5

Examples of professional antigen presenting cells

Answer 5

• Monocyte, Macrophage, Dendritic cell, B-cell

- Contain both MCH 1 and MHC 2

Question 6

What is the APC that initiates adaptive immune response and what are the cells that augment it

Answer 6

Dendritic cells are cells that initiate immune response by activating either CD4 or CD8 T cells
B cells and macrophages only function to augment preexisting immune response

Question 7

MHC 1 presentation pathway

Answer 7

Misfolded viral protein undergo uniquitination and enter endoplasmic reticulum via TAP (Transport associated Protein)

Newly formed MHC 1 molecules located in ER bind to peptides

MHC 1 is then presented at the cell membrane

Question 8

MHC 2 presentation pathway

Answer 8

• MHC 2 molecules are made in the endoplasmic reticulum
• They have invariant chain peptide attached to the antigen binding groove in the ER which prevents intracellular pathogens from binding to MHC 2 complex
• MHC 2 molecule then exits into the endolytic pathway where the invariant chain gets broken down by lysosomal enzymes to form CLIP protein (class 2 associated invariant chain protein)
• Extracellular antigens in the same endosome then replace the CLIP protein before MHC 2 gets presented on Cell surface for antigen presentation

Question 9

Helper T-cells releases cytokines that activate

Answer 9

Macrophage, Neutrophil, Eosinophil

Question 10

T cell activation

Answer 10

Requires signal 1 and signal 2
Signal 1 is given by complementary fit of antigen and MHC receptor to TCR
Signal 2 is commonly given by binding of D7 receptor of dendritic cells to CD28 in T cells
CD40 on dendritic cells also binds to CD40L on T cells to stimulate immune response

Question 11

What happens when there is an absence of both signal 1 and co-stimulatory signal

Answer 11

T cell tolerance is achieved

T cell is not activated