Immune Response

Question 1

What is an antigen? (non self)

Answer 1

Molecules (usually proteins) that can generate an immune response when detected by the body

self antigens would not produce an immune response

Question 2

What is clonal selection and clonal expansion?

Answer 2

Clonal selection - When an antigen enters the body for the first time, B-lymphocytes with complementary receptors to that antigen are stimulated to undergo clonal expansion

Clonal expansion - When a complementary B cell to the antigen is selected, it rapidly clones by mitosis

Question 3

What are antibodies?

Answer 3

Y shaped proteins, known as immunoglobulins,
- Quaternary structure proteins (4 polypeptide chains)
- Secreted by B lymphocytes eg. plasma cells in response to specific antigens
- Bind specifically to antigens forming antigen-antibody complexes

Question 4

Describe the structure of antibodies

Answer 4

• 2 binding sites can bind 2 pathogens at one time
• specificity of antibody depends on its variable regions that form the antigen binding sites

Question 5

What is antigenic variation?

Answer 5

When pathogens change their surface antigens over time due to changes in the genes of pathogens

Question 6

Describe HIV replication in a T cell

Answer 6

• attachment proteins bind to receptors on T cell
• Capsid released into cell where is uncoats and releases the RNA into the cells cytoplasm
• reverse transcriptase converts RNA to DNA and it’s inserted into cells DNA
• viral proteins produced, assembled and released from cell

Question 7

What’s the difference between direct and indirect elisa tests?

Answer 7

Direct used to identify antigens
Indirect used to identify antibodies (use of primary and secondary antibodies)

Question 8

Name 3 techniques the scientists may have used when analysing viral DNA to determine
that the viruses were closely related.

Answer 8

• génome sequencing
• PCR
• electrophoresis

Question 9

What is the role of the disulfide bridge in forming the quaternary structure of an antibody?

Answer 9

Joins two different polypeptides together

Question 10

Give two types of cell, other than pathogens, that can stimulate an immune response.

Answer 10

• abnormal body cells eg cancer cells
• cells form transplants