Hypersensitivity and Autoimmunity

Question 1

Describe the mechanism of Type 1 hypersensitivity

Question 2

Describe the mechanism of Type 2 hypersensitivity

Question 3

Describe the mechanism of Type 3 hypersensitivity

Question 4

Describe the mechanism of Type 4 hypersensitivity

Question 5

Explain how allergens can induce immediate immune responses during early phase allergy

Question 6

Explain the relationship between antibodies (IgE and IgG) and Fc receptors

Question 7

Define atopy

Answer 7

Atopy is essentially the predisposition to allergy.
It can run in families and has to do with abnormally high levels of IgE.

Question 8

Describe the difference between type 2 and type 3 antibody mediated hypersensitivity

Answer 8

Both type 2 and type 3 hypersensitivity involve the usage of the complement and Fc receptors to recruit and activate inflammatory cells.

Type 2:
Type 2 involves antigens that are present in the cell or matrix
The injury is caused by antitissue antibodies.

Type 3:
Type 3 involves soluble antigens (i.e. within plasma)
The injury of the tissue if mediated by an immune complex

Question 9

Describe the factors mediated by T cells to cause tissue damage and autoimmune disease

Answer 9

T cells can cause tissue damage and contribute to autoimmune disease by a number of different factors:
- Producing cytokines: (IL-17, TNF-a, INF-gamma): all of which generally induce inflammation
- Direct cytotoxicity (CD8+ T cells): they directly kill antigens
- Recruitment of other immune cells (macrophages, neutrophils
- Autoantibody production: with help of B cells

Question 10

Define immune tolerance

Answer 10

Immune tolerance is the immune systems ability to recognise the body’s own antibodies and foreign antigens.
Distinguishing between the two can help prevent autoimmune disease, as the body refrains from attacking harmless substances in the body

Question 11

Define autoimmune disease

Answer 11

Autoimmune disease is a failure or breakdown of the immune system that maintains tolerance to self tissues

Question 12

Contrast systemic and organ specific autoimmune disease

Answer 12

Systemic - autoimmune processes spread throughout the body: harder to diagnose.
Organ specific - autoimmune processes are targeted at one organ.

Question 13

Describe some T cell-mediated autoimmune diseases

Answer 13

• Type 1 diabetes
• Multiple sclerosis
• Psoriasis
• Rheumatoid arthritis

Question 14

Describe systemic autoimmune disease

Answer 14

Autoimmune processes is diffuse and spread throughout the body.
It affects more than one organ
= mosaics of diseases and more difficult to diagnose.

Question 15

Describe organ specific autoimmune disease.

Answer 15

Autoimmune process is directed at one org.
(type 2 diabetes - pancreas) (autoimmune thyroiditis)

Question 16

Describe, in detail, type 1 diabetes.

Answer 16

Diabetes arises from a deficiency or inadequate function of glucose.
This leads to glucose metabolism abnormalities - initially ketoacidosis, thirst, excess urine.
Renal failure, heart disease, blindness, neuropathy, etc.

Destruction of the insulin producing Beta cells of the islets of Langhans in the pancreas (main therapy = insulin replacement)

Islet damage is mediated mainly by CD4+h1-T cells that are reactive with islet autoantigens.
Candidate autoantigens include insulin and glutamic acid decarboxylase.

etc….