**Core Concept**
Pernicious anemia is an autoimmune disorder characterized by the deficiency of vitamin B12, leading to impaired DNA synthesis and erythropoiesis. This condition arises due to the body's immune response against a specific protein necessary for intrinsic factor production in the stomach.

**Why the Correct Answer is Right**
In pernicious anemia, autoantibodies are formed against intrinsic factor, a glycoprotein produced by the parietal cells in the stomach. Intrinsic factor is crucial for the absorption of vitamin B12 from food. When autoantibodies bind to intrinsic factor, they neutralize its function, resulting in impaired vitamin B12 absorption and subsequent anemia. This process is mediated by T cells and B cells in the immune system, leading to a chronic inflammatory response against the gastric mucosa.

**Why Each Wrong Option is Incorrect**
**Option A:** Antibodies against parietal cells themselves are seen in autoimmune gastritis, not pernicious anemia.
**Option B:** Autoantibodies against gastric mucosa are associated with other conditions like Zollinger-Ellison syndrome, not pernicious anemia.
**Option C:** Antibodies against gastric mucin are seen in conditions like gastric cancer, not pernicious anemia.

**Clinical Pearl / High-Yield Fact**
Pernicious anemia should be considered in patients with megaloblastic anemia, especially those with a history of gastric surgery, atrophic gastritis, or other autoimmune disorders.

**Correct Answer: A. Antibodies against intrinsic factor.**