Specific Immune Response

Question 1

When do the two types of specific immune response occur?

Answer 1

Humoral = bacterial infection
Cell-mediated = viral infection

Question 2

How do cells become antigen-presenting cells?

Answer 2

Macrophages engulf pathogens, which are packaged into phagosome (phagocytic vacuole)
- Fuses with lyosyme containing digestive enzymes like lysozyme
- Lysozymes digest pathogen membrane, causing it to lyse (breakdown)
- Antigens bind to MHC complex, antigens projected onto cell surface

Question 3

Describe process of humoral response

Answer 3

• Pathogens enter the body, engulfed by macrophage and becomes APC
• MHC complex binds to CD4 receptors on T-helper cells
• T-helpers release cytokines which activate B-cells
• B-cells undergoe clonal expansion —> into plasma and B-memory cells

Question 4

What do plasma cells do?

Answer 4

~ produce many antibodies, specific to antigens, which bind to antigens and cause them to lyse

Question 5

What do B-memory cells do?

Answer 5

Remain in blood to quickly produce antibodies if same pathogen arrives

Question 6

What are antibodies?

Answer 6

Proteins made by B lymphocytes

Question 7

Describe structure of antibodies

Answer 7

Made up of 4 polypeptides; two heavy chains and two light chains
- joined by disulphide bridges
- polypeptides have variable region and constant region
- hinge region in centre allows for flexibility

Question 8

Describe three types of antibodies

Answer 8

• Opsonin = bind to antigens + act as markers for phagocytes, makes phagocytosis quicker
• Agglutinins = bind to antigens + cause clumping
• Anti-toxins = bind to toxins produced by bacteria; phagocytes then engulf these