Apatient received a new heart transplant, but shows signs of graft rejection after 2 weeks. which type of hypersensitivity reaction is in progress? "
a) type i
b) type ii
c) type iii
d) type iv
explain why it wouldnt be the other choices

The answer is d) Type IV.

Hypersensitivity reactions are undesirable reactions of an immune system. There are 4 types of hypersensitivity reactions with different response times:
- Type I: Anaphylactic - The response time is few minutes up to 30 minutes.
- Type II: Cytotoxic - The response time is up to few hours.
- Type III: Immune Complex - The response time is 3-8 hours.
- Type IV: Delayed-type - The response time is 2-3 days or more.
Since all types except Type IV have a short response time, it can be concluded that graft rejection after 2 weeks could belong only to Type IV of hypersensitivity.