Type III Hypersensitivity

Question 0

What are the causes of the 3 types of immune complex disease?

Answer 0

1) persistent infection caused by microbial antigen w/IC deposition in the kidney
2) autoimmunity caused by self antigen w/IC deposition in kidney, skin, joints and arteries
3) extrinsic cause by environmental antigen w/IC deposition in lungs

Question 1

What is the immune mechanism of type III hypersensitivity?

Answer 1

Abs bind with soluble Ag in blood to form insoluble complexes, which deposit in blood vessels. Immune complexes activate complement - chemoattractant and anaphylatoxin. Neutrophil recruitment causes tissue injury.

Question 2

What are the diagnostic tests in type III hypersensitivity?

Answer 2

1) Check complement levels. Levels will be low

2) Biopsy of tissue shows presence of ICs - lumpy, bumpy IC deposits

Question 3

What are clinical examples of type III hypersensitivity?

Answer 3

• Serum sickness, RA, glomerulonephritis, SLE
• Infectious disease: malaria, viral & fungal infections, leprosy
• Occupational disease: Farmer’s lung
• Arthus rxn: skin reddening, edema and necrosis following repeated intradermal injections (seen in pts receiving grass shots). Complement and PMN/platelet activation at a local site.
• Glomerulonephritis post Strep infection