Hypersensitivity and autoimmunity

Question 1

What is an autoimmune disease?

Answer 1

A failure or break down of the immune system which maintains tolerance to self tissues

Question 2

Provide examples of different ways to treat autoimmune disease

Answer 2

Blanket immunosuppression(can lead to infection)
Target selective approach9target the aberrant immune activation whilst leaving the rest of the immune system intact)

Question 3

Define hypersensitivity

Answer 3

Hyper response from immune system

Question 4

How many types of hypersensitivity are there?

Answer 4

4

Question 5

Describe type 1 hypersensitivity

Answer 5

-IgE
-Soluble antigen(allergen)
-Allergy

(• This is where the body recognises an environmental antigen as a pathogen and releases IgE and triggers Mast cell responses.
• During sensitisation, the allergen is shown to a T helper cell by an APC. This causes B cells to differentiate to produce IgE against the antigen.
• From then onwards, exposure to the antigen will cause the release of cytokines from Mast cells, resulting in an allergic response. )

Question 6

Describe type 2 hypersensitivity

Answer 6

-IgG
-Cell or matrix antigen
-AIHA (autoimmune haemolytic anaemia) or rhematic fever

(• In this type, the body’s antibodies bind to the antigens on its own cell surfaces.
• Antibodies are produced in response to the antigens on the cell surfaces e.g. when penicillin binds to blood cells
• IgG and IgM antibodies trigger the complement system causing cell lysis)

Question 7

Describe type 3 sensitivity

Answer 7

-IgG
-Soluble antigen
-SLE
-R. Arthritis
(• This form of hypersensitivity is characterised by the formation of immune complexes (clumps of antibodies that have stuck together)
• A LOW conc. of antibody coupled with a LARGE conc. of antigen causes small complexes to form)

Question 8

Describe type 4 sensitivity

Answer 8

• Th1, Th2, CTL
• soluble antigen, cell
• antigen,inf-gamma
  Type 1 diabetes, MS, RA
  (• The body’s CD4 helper T cells recognise the foreign antigen, and starts to produce cytokines which leads to an inflammatory response. )

Question 9

Describe central tolerance

Answer 9

The process of eliminating lymphocytes that are self reactive

Question 10

Describe peripheral tolerance

Answer 10

The process of eliminating T cells which avoided central tolerance

Question 11

What type of lymphocytes acquire peripheral tolerance?

Answer 11

Mature lymphocytes in the peripheral tissue

Question 12

What type of lymphocytes acquire central tolerance

Answer 12

Immature lymphocytes during their development

Question 13

How may self reactive lymphocytes escape negative selection?

Answer 13

due to low affinity to self MHC/antigen and the exclusive expression of some proteins in the periphery

Question 14

Name some factors which affect auto-immune diseases?

Answer 14

genetic predispositions
Hormonal/sex
Environmental co-factors
immunity regulatory factors

Question 15

Describe systemic autoimunne disease

Answer 15

Systemic
Autoimmune process is spread throughout the body - affects more than one organ. eg systemic lupus erythematosus (SLE)

Question 16

Describe organ specific autoimmune disease

Answer 16

Autoimmune process directed against one organ. eg type 1 diabetes

Question 17

What type of hypersensitivity is SLE

Answer 17

type 3

Question 18

What type of hypersensitivity is diabetes mellitus

Answer 18

type 4

Question 19

What type of hypersensitivity is R. arthritis

Answer 19

Type 3 and 4

Question 20

Compare early and late phase responses

Answer 20

Early phase response
-occurs within minutes
-preformed mast cells mediators(histamin, heparin, chemotactic factors)
Late phase response
-New synthesised mediators (prosaglandins,leukotrienes)
-Th2 cytokins
Eosinophil mediators