Hypersensitivity and Immune Tolerance

Question 1

What is immunological tolerance?

Answer 1

specific unresponsiveness to self Ags

Question 2

What is an example of a complex antigen?

Answer 2

bacteria -> has many epitopes

Question 3

What are adjuvants?

Answer 3

added to Ag to stimulate response to Ag

Question 4

How do adjuvants work?

Answer 4

• enhance cytokine production
• extend presence of Ag to activate macrophages and lymphocytes

Question 5

What is central tolerance?

Answer 5

• occurs in thymus or bone marrow
• wants cells to recognize self; if recognition is too strong -> apoptosis
• generation of regulatory T cells -> CD4/ CD25/ Foxp3

Question 6

What is peripheral tolerance?

Answer 6

• occurs in secondary lymphoid organs
• T cells recognize Ags but do not respond

Question 7

What are the mechanisms that prevent self reaction in peripheral tolerance?

Answer 7

• anergy of slef-reacting cells
• T cell recognizes Ag without strong co-stimulation
• death of self-reacting cells
• suppression by regulatory T cells

Question 8

What are the types of CD4 cells?

Answer 8

• Th1
• Th2
• Th17
• T regs -> CD4, CD25, Foxp3

Question 9

What is IPEX syndrome?

Answer 9

• mutation in Foxp3
• lack of central tolerance

Question 10

What is polyendocrine syndrome?

Answer 10

• mutated AIRE gene
• self Ags are not expressed in thymus
• lack of negative selection -> can respond to self

Question 11

What are the responses in peripheral T cell tolerance?

Answer 11

• normal response -> effector and memory T cells
• anergy -> functional unresponsiveness
• suppression -> block in activation
• deletion -> apoptosis

Question 12

What are the 2 types of T cells antigens in B cell tolerance?

Answer 12

• dependendent -> tolerance can be generated via T cells
• independent -> tolerance at the level of B cell

Question 13

What are the characteristics of organ-specific autoimmunity?

Answer 13

• occurs when one organ is targeted
• treated with organ-specfific corrections
• ex: diabetes type 1 -> treated with insulin

Question 14

What are the characteristics of systemic autoimmunity?

Answer 14

• widespread inflammation
• treated by general down-regulation of IS
• ex: rheumatoid arthritis -> treated with steroids

Question 15

What is associated with ankylosing spondylitis?

Answer 15

HLA-B27

Question 16

What are the factors involved with infections & autoimmunity?

Answer 16

• cross-section -> “little women” (rheumatic fever)
• bystander effect
• removal of sequestration
• adjuvant effect

Question 17

What is type 1 hypersensitivity?

Answer 17

• mediated by IgE
• immediate -> seconds to minutes
• wheal and flar reaction
• Th2 response
• ex: allergic reactions

Question 18

What is type 2 hypersensitivity?

Answer 18

• mediated by IgG & IgM
• auto Abs bind to self Ags and trigger immune response
• activates compliemtn system
• ex: rehumatic fever, graves disease, hashimoto disease

Question 19

What is type 3 hypersensitivity?

Answer 19

• mediated by immune complexes
• complexes build up in blood vessels and kidney -> serum sickness
• ex: lupus & rheumatoid arthritis

Question 20

What is type 4 hypersensitivity?

Answer 20

• mediated by T cells
• delayed reaction -> 24-48 hours after exposure
• contact sensitivity
• cytokine release leads to tissue injury
• ex: reaction to tuberculosis skin test