Adaptive Immunity

Question 1

What are the main cells involved in immunity?

Answer 1

Leukocytes (white blood cells), even though they are only a minor constituent of blood

Question 2

Describe antigen sampling and presentation

Answer 2

• Dendritic cells (DC) are present in major organs
• They phagocytose antigen and process it down to peptides
• DC migrate from organs (eg. skin) to draining lymph node
• They present peptides on MHC to other whit blood cells (called T cells)

Question 3

Describe adaptive immunity

Answer 3

• Dendritic cells (DC) present peptides on MHC to T cells
• CD4 T cells help B cells make antibody
• CD8 T cells become cytotoxic and kill virus infected cells and cancer cells

Question 4

What is the purpose of antigen uptake?

Answer 4

• Clearance of pathogens (innate response) - neutrophils come into the blood rapidly and clear pathogens
• For presentation to T cells (adaptive response

Question 5

What occurred 500 million years ago to our immune system?

Answer 5

Phagocytes evolved to keep remnants of pathogens and display these to other cells of the immune system
This was the beginning of the adaptive immune response.

Question 6

Describe the evolution of immunity

Answer 6

• Invertebrates have innate immunity only
• Vertebrates have both innate and adaptive immunity
  Jawless fish are vertebrates who have innate and adaptive immunity but their adaptive immune system is based on different structures.

Question 7

Describe MHC-I antigen processing

Answer 7

• Antigenic proteins are degraded to peptides in cytoplasm by an enzyme called a proteosome
• Peptides are imported into endoplasmic reticulum (ER)
• Peptide loading of MHC-I takes place in ER

Question 8

Describe MHC-II antigenic processing

Answer 8

• Antigenic proteins are degraded in acidic phagolysosome
• Peptide loading of MHC-II takes place in phagolysososme