Hypersensitivity pneumonitis is classically described as a - (AIPG, 2011)
|A||Type I hypersensitivity reaction|
|B||Type II hypersensitivity reaction|
|C||Type III (Immune complex) hypersensitivity|
|D||Type IV (cell mediate(d) hypersensitivity|
a. Hypersensitivity pneumonitis is an immunologically mediated response to an extrinsic antigen that involves both immune complex (type Ill) and delayed (type IV) hypersensitivity reaction.
b. But the best answer here is 'c' i.e. type III hypersensitivity (as we have to choose one answer) :
c. "Classically, hypersensitivity pneumonitis was believed to be a immune complex mediated (type lIl) hypersensitivity" .
d. "Acute hypersensitivity pneumonitis is a type III immune complex mediated hypersensitivity reaction" ... Morgan 4'"/e p. 970
However, for exams like PGI Chandigarh, both option c & d are correct.