Lecture 8: Antibodies in infection

Question 1

Describe antigen transport;

Answer 1

Dendritic cells i.e macrophages i.e langerhan cells. This is transported through lymphatics to lymph node. (Antigen presenting cell, have antigen fragments on surface). Antigen specific cells are recruited to initiate immune response.

Question 2

Why is adaptive immunity important in auto-immunity?

Answer 2

Central tolerance develops and prevents auto-immunee reactions.

Question 3

What are lymphocyte sub-populations?

Answer 3

Effector response;

• B-cells (AB production)
• CD8 T cells (Antigen specific cytotoxicity)

NK cells

Regulatory responses
- CD4 t cells

Question 4

Write some notes on shape recognition;

Answer 4

• Common components of many microbes i.e bacterial cell wall sugars
• Uncommon components of particular microbes i.e viral caspid protein
• Common components in uncommon context i.e myocardium shapes on strep. bacteria.

Question 5

How are lymphocytes activated?

Answer 5

Antigen fragment is presented to surface immunoglobulin of lymphocyte, binding occurs and causes conformational change and this activates the lymphocyte.

Question 6

How does affinity of binding influence lymphocyte activation?

Answer 6

Binding does not have to be perfect.

1) Implication of this is that we can identify a broad range of pathogens with a finite number of B and T cells
2) A low affinity reaction may crossreact with something else with higher affinity i.e self reaction

Question 7

Describe the structure of antibodies;

Answer 7

Heavy chain (Contains FC region)
Two light chains (Half constant region and half hypervariable region)

Question 8

Describe what each part of the antibody is responsible for;

Answer 8

Heavy chain, contains FC region and compliment binding region.

The light chain contains the hypervariable region which forms the binding cleft.

Question 9

How long does it take for babies to develop their own antibodies?

Answer 9

1-2 months and this rises dramatically to 2-3 months

Question 10

How does antibody response change after immunity is developed?

Answer 10

1st antibody response takes a long time and is small

2nd antibody response is very quick and much larger (adaptive response)

Question 11

What is B cell clonal activation?

Answer 11

Each B cell is committed to one antigen binding shape. once activated it receives helper signals to confirm activation and divides into plasma cells that secrete the specific antibody and antigen specific memory cells.

Question 12

What are the four uses of antibodies?

Answer 12

1. Direct neutralisation
2. Opsonisation
3. Antibody-dependant cellular cytotoxicity
4. Complement activation

Question 13

Write some notes on direct neutralisation;

Answer 13

Antibodies coat virus and prevent it from attaching to cells and thus no infection

Question 14

Write some notes on opsonisation;

Answer 14

Antibodies opsonise bacteria and enhance phagocytosis

Question 15

Write some notes on Antibody-dependant cellular cytotoxicity;

Answer 15

Antibodies coat bacteria and activate K cells to release short range factors, killing coated bacteria

Question 16

Write some notes on compliment cascade activation;

Answer 16

Antigen-antibody complexes activate the compliment cascade (known as the classical pathway)

=
Chemotaxis
Opsonisation
Killing of pathogens (lysis)

Question 17

Whats it called when the common cell wall component of bacteria activates the compliment cascade?

Answer 17

Alterative pathway