immune tolerance part 1+2

Question 1

define immune regulation

Answer 1

control of the immune response to prevent inappropriate reactions

Question 2

give two reasons why immune regulation is required

Answer 2

.avoid excessive lymphocyte activation and tissue damage

. prevents inappropriate reactions against self antigens (tolerance)

Question 3

what is meant by pathologic

Answer 3

immune response against self antigen

Question 4

disorders are often classified as …

Answer 4

immune mediated inflammatory diseases

Question 5

immune mediated inflammatory diseases can either be …. or ….

Answer 5

systemic, organ-specific

Question 6

give 3 examples of chronic inflammatory diseases

Answer 6

psoriasis, rheumatoid arthiritis, lupus

Question 7

What are the three phases of cell mediated immunity

Answer 7

induction
effector
memory

Question 8

describe the steps of cell mediated immunity

Answer 8

1) cell infected dendritic cell (DC) collects material
2) MHC: peptide TCR interaction
3) Naive t cells become effectors
4) effector cells sees MHC: Peptide on infected cells performs function
5) effector pool contracts to memory

Question 9

what is the cardinal feature of ALL immune responses

Answer 9

self limitation

Question 10

explain self limitation

Answer 10

.immune response eliminates antigens that initiated the response

hence first signal for lymphocyte activation is eliminated

Question 11

what licences a cell response

Answer 11

.antigen recognition
. Co-stimulation
. cytokine release

Question 12

what are the three possible outcomes from an immune response

Answer 12

resolution: .no tissue damage
.phagocytosis of debris by macrophages

repair: . healing with scar tissue and regeneration
. Fibroblasts and collagen synthesise

chronic inflammation: ACTIVE INFLAMMATION AND ATTEMPTS TO REPAIR DAMAGE ONGOING

Question 13

define tolerance

Answer 13

specific unresponsiveness to an antigen that is induced by exposure of lymphocytes to that antigen

Question 14

Give 2 significant features of tolerance

Answer 14

All individuals HAVE tolerance to self antigens where breakdown of this phenomena is autoimmunity

Theraputic potential which can treat autoimmune disease and prevent graft rejection

Question 15

when does tolerance occurs

Answer 15

Before T/B cells enter circulation (central)
In circulation (peripheral)

Question 16

define central tolerance

Answer 16

destroys T/B cells before they enter circulation

Question 17

How does B-cell selection for central tolerance occur

Answer 17

Immature B cell encounters antigen in form which cross links their IgM triggering apoptosis

Question 18

How does T-cell selection for central tolerance occur

Answer 18

.Need to select for TCR which can bind to self MHC/self peptides

Question 19

what happens if T cell doesn’t bind to any self-MHC

Answer 19

apoptosis

Question 20

what happens if T cell binds too strongly to MHC?

Answer 20

apoptosis-NEGATIVE selection (no survival)

Question 21

what happens if T cell binds too weakly to MHC?

Answer 21

Positive selection. (survival)

Question 22

How can a T cell developing in the thymus encounter MHC bearing peptides expressed in other parts of the body?

Answer 22

A specialised transcription factor allows thymic expression of genes that are expressed in peripheral tissues

AIRE promotes self tolerance by allowing the thymic expression of genes from other tissues

Mutations in AIRE result in multi-organ autoimmunity (Autoimmune Polyendocrinopathy Syndrome type 1)

Question 23

define peripheral tolerance

Answer 23

destroy or control any self reactive T/B cells which do enter circulation

Question 24

what is AIRE

Answer 24

AutoImmune REgulator (AIRE

Question 25

what determines B cell antigen specificity?

Answer 25

BCR

Question 26

what does BCR consist of?

Answer 26

1 heavy chain

1 light chain

Question 27

what happens to B cells after antigen exposure

Answer 27

.Antibody production
.Memory
.Affinity maturation-process whereby the immune system generates antibodies of higher affinities during a response to antigen.

Question 28

true or false: B and T cells can change specificity after leaving bone marrow (somatic hypermutation)

Answer 28

False- only B cells can undergo somatic hypermutation

Question 29

define anergy

Answer 29

lack of response by body’s defence mechanism against foreign substances

Question 30

describe how peripheral tolerance occurs in T cells

Answer 30

. Naive T cells need Co-stimulatory Signals (CSS) TO BECOME activated

. most cells lack CSS and MHC CLASS II molecules

naive T cell meets MHC/PEPTIDE ligand without appropriate Co-stimulatory protein hence becomes anergic
cells less likely to be stimulated in future even if Co-stimulation is present

Question 31

describe how ignorance causes peripheral tolerance

Answer 31

.Antigen may be too low of concentration for TCR to be triggered e.g immunological privileged sights such as eye, brain

Question 32

Explain Antigen Induced Cell Death (AICD)

Answer 32

.Activation of the TCR can result in apoptosis

. in peripheral T cells is often caused by induction of expression of the death ligand: Fas Ligand (CD95,FasL)