Hypersensitivity and Autoimmunity

Question 1

Give an account of Type I Hypersensitivity

Answer 1

• Body recognises foreign antigen as pathogen and releases IgE, triggering mast cell responses
• During sensitisation, the antigen is shown to T helper cells by an antigen-presenting cell (APC), causing B cells to differentiate to produce IgE against the antigen
• After that, exposure to the antigen will trigger the release of cytokines from mast cells which results in an allergic response

Question 2

Give an account of Type II Hypersensitivity

Answer 2

• Antibodies bind to antigens on the body’s own cells surfaces
• Antibodies are produced in response to (e.g. penicillin binding to antigens on RBC’s)
• IgM and IgG trigger the complement system which causes cell lysis

Question 3

Give an account of Type III Hypersensitivity

Answer 3

• Characterised by formation of immune complexes (clumps of antibodies)
• A low concentration of antibody coupled with a high concentration of antigens causes complexes to form

Question 4

Give an account of Type IV Hypersensitivity

Answer 4

-The body’s CD4 helper T cells recognise foreign antigens and release cytokines, causing an inflammatory response