Final answer:
Pernicious anemia, a human antibody-mediated disease associated with type II hypersensitivity, results in impaired absorption of vitamin B12 due to an autoimmune response targeting intrinsic factor or gastric parietal cells.
Step-by-step explanation:
Human antibody-mediated diseases, specifically type II hypersensitivity reactions, often result in the targeting and destruction of various cellular components within the body. These reactions involve the binding of IgG or IgM antibodies to cell-surface antigens, with pernicious anemia being an example of such a disease. Pernicious anemia is characterized by the impaired absorption of vitamin B12, which is essential for the production of red blood cells.
In type II hypersensitivity, cell damage is caused by the binding of antibody and the activation of complement, usually against red blood cells. This can occur, for instance, during a mismatched blood transfusion, leading to hemolytic anemia. However, in pernicious anemia, the autoimmune response targets the intrinsic factor or the gastric parietal cells that are crucial for vitamin B12 absorption in the intestine, rather than directly targeting red blood cells.