Hypersensitivity reactions

Question 1

Type 1

Answer 1

• allergic or immediate
• onset within minutes
• develop igE antibodies
• IgE formed as a result of prior sensitisation and coats mast cells and basophils
• release of histamine and other mediators

Question 2

Type 2

Answer 2

-cytotoxic
-onset within minutes or a few hours
-involves IgG or IgM
5 mechanisms:
1.complement mediated lysis
2.complement activation and fc-mediated immune cell activation
3.opsonization->phagocytosis
4.antibody dependent cell mediated cytotoxicity (NK cells)
5.inhibition or activation of downstream signalling pathways

Question 3

Type 3

Answer 3

• immune complex
• onset usually within 2-6 hours
• can be local or systemic
• causes release of anaphylatoxins which increase vascular permeability
• chemokinesis attracts neutrophils-degranulation-inflammation
• get an antigen-antigen complex like in type 2 however the antibody attacks an antigen in blood stream

Question 4

Type 4

Answer 4

• delayed hypersensitivity
• inflammation by 2-6 hours, peaks by 24-48 hours
• T cell mediated
• CD4+ antigen penetrates the skin->uptake by langerhans->migration to lymph nodes and formation of sensitised T lymphocytes
• CD8+ release perforin and granzymes

Question 5

Type 1 summary

Answer 5

• IgE
• exogenous
• 15-30 minutes
• weal and flare appearance
• basophils and eosinophils
• antibody
• allergic asthma and hay fever

Question 6

Type 2 summary

Answer 6

• IgG and IgM
• cell surface antigen
• minutes-hours
• lysis and necrosis
• antibody and complement
• transferred with antibody
• erythroblastosis fettles and good pasture’s nephritis

Question 7

Type 3 summary

Answer 7

• IgG and IgM
• soluble
• 3-8 hours
• erthema and edema,necrosis
• complement and neutrophils
• antibody
• SLE,farmer’s lung disease

Question 8

Type 4 summary

Answer 8

• no antibodies
• tissues and organs
• 48-72 hours
• erythema and induration
• monocytes and lymphocytes
• T-cells
• tuberculin test, poison ivy and granuloma