**Core Concept**
Gluten-sensitive enteropathy, also known as celiac disease, is a chronic autoimmune disorder triggered by the ingestion of gluten in genetically susceptible individuals. The disease is characterized by small intestinal villous atrophy, leading to malabsorption of nutrients. A specific human leukocyte antigen (HLA) marker is associated with the susceptibility to this condition.

**Why the Correct Answer is Right**
The HLA marker associated with gluten-sensitive enteropathy is HLA-DQ2. This marker is a result of a genetic predisposition, where individuals with HLA-DQ2 are more likely to develop the disease upon exposure to gluten. The HLA-DQ2 molecule is involved in the presentation of gluten peptides to T-cells, leading to an immune response and subsequent intestinal damage. The presence of HLA-DQ2 is considered a diagnostic marker for celiac disease, although it is not exclusive to this condition.

**Why Each Wrong Option is Incorrect**
**Option A:** HLA-B27 - This HLA marker is associated with various autoimmune and rheumatic conditions, such as ankylosing spondylitis, but not with gluten-sensitive enteropathy.
**Option B:** HLA-DR4 - While HLA-DR4 is associated with autoimmune disorders, it is not specifically linked to gluten-sensitive enteropathy.
**Option C:** HLA-A2 - This HLA marker is not associated with any autoimmune conditions related to gluten ingestion.

**Clinical Pearl / High-Yield Fact**
Celiac disease is often underdiagnosed or misdiagnosed, as the symptoms can be nonspecific and vary widely among individuals. However, the presence of HLA-DQ2 can help clinicians suspect this condition in patients with unexplained gastrointestinal symptoms or malabsorption.

**Correct Answer: D. HLA-DQ2**