Final answer:
Delayed hypersensitivity, or type IV hypersensitivity, is a cellular immune response that occurs after re-exposure to an antigen. In HIV patients, this reaction is seen in 2-8% of cases and is associated with the HLA-B*57:01 allele.
Step-by-step explanation:
Delayed hypersensitivity, also known as type IV hypersensitivity, is a cellular immune response that occurs after re-exposure to an antigen. In this type of hypersensitivity, sensitized T cells, specifically Th1 cells, release cytokines that activate macrophages. The resulting inflammatory response can cause tissue damage.
In the case of HIV patients, type IV hypersensitivity occurs in 2-8% of cases and is strongly associated with the HLA-B*57:01 allele. This means that individuals with this allele have a higher risk of developing a delayed hypersensitivity reaction to the virus.