Immunological Tolerance, Autoimmunity and Hypersensitivity

Question 1

Where is central tolerance induced?

Answer 1

Thymus or Bone Marrow

Question 2

What is immunological tolerance?

Answer 2

Self tolerance

Question 3

Where is peripheral tolerance induced?

Answer 3

Peripheral tissues (lymph nodes)

Question 4

What is negative selection?

Answer 4

Deletion of T cells in the thymus if a T cell recognizes self antigens

Question 5

What is peripheral tolerance?

Answer 5

Antigen recognition without adequate costimulation renders mature T cells sensitive to peripheral tolerance

Question 6

What is anergy?

Answer 6

Cell is turned off not killed; functional unresponsiveness

Question 7

What is suppression?

Answer 7

Blocked activation of T cell

Question 8

What is deletion?

Answer 8

Apoptosis

Question 9

What are characteristics of T regulatory cells?

Answer 9

CD4+; require the FoxP3 transcription factor; develop in thymus or periphery; express high levels of CD25 (alpha chain of IL-2 receptor)

Question 10

What are the two fates of a B cell if it has STRONG self reactivity in bone marrow?

Answer 10

Receptor editing: change Ig specificity by expressing a new Ig light chain
Deletion (apoptosis)

Question 11

How do T regulatory cells function to suppress T cells?

Answer 11

Produce cytokines that inhibit activation of immune cells
Express CTLA-4 which blocks/deletes B7 on APCs
Depleting supply of IL-2

Question 12

What is the fate of a B cell with WEAK self reactivity in bone marrow?

Answer 12

Anergy and reduced receptors

Question 13

Difference between affinity and avidity?

Answer 13

Affinity: how strong the attraction is
Avidity: the strength of binding

Question 14

Mutations in which alleles correlate with autoimmune diseases?

Answer 14

HLA

Question 15

What are the 4 types of hypersensitivity reactions?

Answer 15

Type I/Immediate hypersensitivity (allergies)
Type II/Antibody-mediated diseases
Type III/Immune complex-mediated diseases
Type IV/T cell-mediated diseases

Question 16

What happens in Type I hypersensitivity?

Answer 16

IgE is produced by B cells which bind to the FCEpsilonRI on mast cells

Question 17

What happens in Type II hypersensitivity?

Answer 17

Cross reactive antibodies bind to tissues recruiting inflammatory cells

Question 18

What happens in Type III hypersensitivity?

Answer 18

Cross reactive antibodies bind in circulation depositing in blood vessels and recruit complement creating damage

Question 19

What happens in Type IV hypersensitivity?

Answer 19

Either CD4+ cells release cytokines causing inflammation and release of ROS or CD8+ cells bind and kill healthy cells