Abnormal Immune Responses

Question 1

Normally, there are two types of immune responses. What are they?

Answer 1

1) humoral/antibody mediated

2) cell mediated

Question 2

What are the three types of abnormal immune responses?

Answer 2

1) hypersensitivity
2) immunodeficiency
3) autoimmunity

Question 3

What is immunodeficiency?

Answer 3

abnormal immune response (can be partial, deficient or absent)

Question 4

With regards to etiology, what are the two types of immunodeficiency?

Answer 4

1) primary - congenital or genetic (ex. problem with development of thymus)
2) secondary - acquired/postnatal (ex. from immunosuppressant drugs, infection, cancer)

Question 5

What are five types of immunodeficiency?

Answer 5

1) T cell disorders
2) B cell disorders
3) T and B cell disorders
4) complement disorders
5) phagocytosis disorders

Question 6

How is immunodeficiency treated?

Answer 6

• replacement therapy (gamma globulins)

- transplant (ex. bone marrow)… limited success

Question 7

What is a hypersensitivity?

Answer 7

an inappropriate or exaggerated immune response

Question 8

What are the four types of hypersensitivity?

Answer 8

type 1 - allergy or IgE mediated hypersensitivity
type 2 - cytotoxic hypersensitivity
type 3 - immune mediated hypersensitivity
type 4 - delayed or T-cell mediated hypersensitivity

Question 9

Which type of hypersensitivities involve antibodies? T cells?

Answer 9

Types 1, 2, and 3 involve antibodies. Type 4 involves T cells.

Question 10

What are the two processes involved in a type 1 hypersensitivity? Explain what happens in each process.

Answer 10

1) sensitization
- exposed to antigen for first time
- with help of T cells, B cells produce IgE antibodies
- IgE antibodies attach to surface of mast cells

2) re-exposure
- if patient is re-exposed to antigen… allergic reaction
- antigen/antibody complex (immune complex) forms
- mast cell degranulates, releases mediators that lead to inflammation
- target area becomes red and swollen

Question 11

Explain what happens in a type 2 hypersensitivity. Give an example.

Answer 11

• IgM or IgG mediated
• antibodies mis-target self antigens on cell surface
• antibodies and antigen form immune complex
• causes destruction of self cell by complement or phagocytosis
• causes injury and inflammation
• episodic

ex. mismatched blood transfusion

Question 12

Explain what happens in a type 3 hypersensitivity.

Answer 12

• immune complex not broken down because it is too small or insoluble
• immune complex continues to circulate in blood
• immune complex deposited on endothelium in slower flow areas (capillaries)
• macrophages come to remove… cause tissue damage in the process, trigger inflammation

ex. glomerulonephritis, rheumatoid arthritis

Question 13

Explain what happens in a type 4 hypersensitivity.

Answer 13

• cytotoxic T cells misrecognize self-antigens
• cytotoxic T cells destroy self-cells
• causes inflammation and tissue damage
• can be direct or delayed

ex. contact dermatitis

Question 14

What is autoimmunity?

Answer 14

when body loses ability to tell self from non-self (loses self tolerance), causing antibodies to target self-antigens and destroy self cells

Question 15

What causes autoimmunity?

Answer 15

1) abnormal T cell activity - ex. faulty T suppressor cells don’t stop cytotoxic T cell production after antigen is destroyed and T cells go on to target self cells
2) molecular mimicry - self cells have very similar epitope to an antigen and body mistakes self cells for the antigen
3) previously masked self-antigens are exposed - cells from development that were previously closed off are now exposed by disease or injury, the immune system doesn’t recognize it as self