**Core Concept**
HLA-B*1502 is a specific allele of the human leukocyte antigen (HLA) system, which plays a crucial role in the immune system. The HLA system is responsible for presenting antigens to T-lymphocytes, and certain alleles have been associated with increased susceptibility to specific diseases.

**Why the Correct Answer is Right**
HLA-B*1502 is strongly associated with carbamazepine-induced Stevens-Johnson syndrome and toxic epidermal necrolysis (SJS/TEN) in certain populations, particularly in Southeast Asians. This association is thought to be due to the allele's ability to present carbamazepine as a hapten, leading to an immune response against the medication. The HLA-B*1502 allele is encoded by the HLA-B gene on chromosome 6, and its expression is necessary for the presentation of carbamazepine to T-lymphocytes.

**Why Each Wrong Option is Incorrect**
* **Option A:** HLA-B*1502 is not associated with a higher risk of developing graft-versus-host disease after bone marrow transplantation. Graft-versus-host disease is primarily related to mismatches in other HLA alleles.
* **Option B:** HLA-B*1502 is not linked to an increased risk of developing pemphigus vulgaris, an autoimmune disease characterized by blistering of the skin and mucous membranes. Pemphigus vulgaris is associated with other HLA alleles, such as HLA-DR4 and HLA-DR6.
* **Option C:** HLA-B*1502 is not a marker for increased susceptibility to HIV infection. While certain HLA alleles, such as HLA-B*35 and HLA-B*57, are associated with a higher risk of HIV infection and disease progression, HLA-B*1502 is not one of them.

**Clinical Pearl / High-Yield Fact**
When prescribing carbamazepine, especially in Southeast Asian patients, it is essential to screen for the presence of the HLA-B*1502 allele to minimize the risk of SJS/TEN.

**Correct Answer:** D.