Lecture 8

Question 1

What are the four types of immuno-pathologies?

Answer 1

1.	Insufficiency of immune response 
•	Inherited and acquired immunodeficiencies  
2.	Over-activity of the immune response 
•	Hypersensitivities & allergies 
3.	Disruptions to self-tolerance
•	Autoimmune disease 
4.	Neoplasia’s and the immune system 
•	Lymphomas and leukemias

Question 2

What type of immunodeficiency would cause pyogenic (pus forming) bacteria?

Answer 2

• antibody, phagocytes, complement

Question 3

What type of immunodeficiency would cause fungal infection?

Answer 3

• CD4+ T cells, antibody

Question 4

What type of immunodeficiency would cause viral/intracellular bacteria?

Answer 4

• CD8+ T cells, natural killer cells

Question 5

What is a type 1-hypersensitivity?

Answer 5

• IgE mediates mast cell degranulation

Question 6

What is a type 2- hypersensitivity?

Answer 6

• IgG mediated cellular toxicity

Question 7

What is a type 3-hypersensitivity?

Answer 7

• Immune complex mediated (IgG, IgM)

Question 8

What is involved in a type 4 hypersensitivity?

Answer 8

• Cell mediated CD4 or CD8

- Delayed type (DTH)

Question 9

Explain the mechanisms of Type 1- hypersensitivity:

Answer 9

1. The pollen is phagocytosed by a dendritic cell that then activates a naive T-cell turning it into a TH2 helper cell
2. The TH2 cell then helps a IGE class switching B cell
3. This then stimulates the production of an IGE secreting B-cell
4. The binding of IgE to FcRI on mast cells then occurs
5. Repeat exposure to the allergen then occurs
6. Activation of mast cell then stimulates the release of mediators
7. Mediators include vasoactive amines and lipid mediators that cause immediate hypersensitivity reaction (minutes after repeat exposure to the allergen). Furthermore, a late phase reaction occurs (2-24 hours after exposure to initial antigen)

Question 10

Briefly explain why immunological self tolerance occurs:

Answer 10

1. All body proteins have the capacity to be an antigen
2. Potentially self reactive lymphocytes and randomly generated during development
3. The immune system must be educated to “tolerate” or ignore self proteins, but still respond to foreign material (most self reactive lymphocytes are screened and deleted during maturation)
4. This is not 100% effective however as some self-reactive lymphocytes escape deletion and must be controlled in periphery (peripheral tolerance)

Question 11

What are the mechanisms of self tolerance?

Answer 11

1. Ignorance
2. Anergy
3. Apoptosis
4. Regulation