Autoimmunity

Question 1

Autoimmunity

Answer 1

Failure of self-tolerance to eliminate self-reactive T and B lymphocytes into circulation
- presentation of an auto-antigen by APC allowing excessive activation of T cells

Question 2

The key to autoimmunity is the ______

Answer 2

Loss of self tolerance

Question 3

Immunological self tolerance

Answer 3

Ability to tolerate self-antigens that encompass the tissues of the body

Question 4

Central tolerance

Answer 4

Immature T cells

- must pass positive and negative selection in the thymus before entering the periphery

Question 5

Positive selection

Answer 5

Occurs in the thymic cortex

• immature T cell must prove that it has a TCR capable of interacting with a peptide antigen presented by MHC
• T cells that do not pass die by apoptosis

Question 6

Negative selection

Answer 6

Occurs in the thymic medulla

• immature T cell must prove that it’s TCR is not capable of responding to self-antigens with high affinity
• cells interact with thymic DC that contain self-proteins

Question 7

TCRs ____ a high affinity for self-proteins pass the test

Answer 7

Without!

Question 8

Maturation of B cells

Answer 8

Immature B cells undergo similar process to negative selection
- derive in the bone marrow, final stages occur in extramedullary locations (ex: Peyer’s patches)

Question 9

Receptor editing

Answer 9

Interaction of BCR with self-antigens may lead to deletion or gene rearrangements and expression of a new BCR
- if new BCR is NOT self reactive, cell maturation will continue

Question 10

Peripheral tolerance

Answer 10

Occurs in peripheral lymphoid organs

- cells that escape central censorship are controlled by apoptosis and Tregs

Question 11

Tregs

Answer 11

Regulatory cells that suppress immune responses of other cells

Question 12

T cell activation

Answer 12

• Tc: destruction of target cell (NK and cytotoxic T cells)
• Th1: IL-2, IFN-gamma
• Thj2: IL-4, IL-5, IL-9, IL-14

Question 13

B cell activation

Answer 13

Plasma cells –> antibody secretion

Question 14

Autoimmune diseases may involve

Answer 14

Specific organs or multiple body systems and both humoral and cellular mechanisms of tissue damage

Question 15

Organ specific

Answer 15

Immune reactions to a specific tissue antigen

Question 16

Non-organ specific

Answer 16

Immune response to dispersed antigens which leads to systemic deposition of immune complexes

Question 17

Autoimmune diseases are more common in ____

Answer 17

Dogs

• less common in cats/horses
• sporadic in production animals

Question 18

Autoimmunity causes

Answer 18

• genetic predisposition
• infectious diseases
• predisposing factors (age, gender, etc)
• drugs, vaccines
• environmental
• hormonal influences
• cancer

Question 19

Primary

Answer 19

Absence of any identifiable trigger factor

• idiopathic
• true immune mediated disease
• diagnosis of exclusion

Question 20

Secondary

Answer 20

Underlying trigger factor

- need to get rid of secondary cause to treat

Question 21

Mononuclear phagocyte system

Answer 21

Removes old erythrocytes in the liver and spleen

- identifies antibodies against membrane bound antigens

Question 22

IMHA

Answer 22

Premature destruction of erythrocytes

• immune response directly/indirectly targets RBCs
• anti-RBC antibodies bind to RBC membrane

Question 23

Primary IMHA

Answer 23

Predominant form

• idiopathic
• immune response to self-antigens –> antibodies cover RBC –> gets destroyed by macrophages

Question 24

Extravascular hemolysis

Answer 24

Secondary

• antibodies are directed against foreign antigens located inside RBC
• end product is the same as primary = RBC destruction

Question 25

MIcroorganisms

Answer 25

Infects or attaches to membrane of host cell - cell surface expression of microbial antigen - appropriate immune response - non specifically destroys the host cell

Question 26

Secondary immune-mediated disease causes

Answer 26

- inflammation - infection - neoplasia - drugs - tick borne infection - post vaccination - bee sting

Question 27

Infectious triggers

Answer 27

Most significant trigger for autoimmunity - immediately after infection or lag time - viral infection: activation of numerous clones of B cells, or non specifically activate B cells and autoantibodies

Question 28

Drugs and vaccines

Answer 28

Act as a hapten, binds to membrane of a cell to form a target of an immune response - may modify the structure of a self-protein

Question 29

Secondary immune mediated treatment

Answer 29

Treat underlying condition - supportive care - immunosuppressive therapy

Question 30

Genetic predisposition

Answer 30

Genetic etiology is perpetuated in a population | - gene most strongly linked to autoimmunity - MHC, presenting self-antigens to auto-reactive T cells

Question 31

Intravascular hemolysis

Answer 31

Antibodies AND complement coats the RBC = osmotic cell lysis