There are two antibodies that are commonly used to diagnose Pernicious Anemia and can be measured in the blood. These are called auto-antibodies because they are generated by the immune system for unknown reasons, but react with two target antigens in the stomach. The one antibody attacks the parietal cells in the stomach that make Intrinsic Factor (the protein that binds to vitamin B12 from the diet and is needed for absorption) and the other antibody targets Intrinsic Factor itself. Anti-parietal antibodies can be found in individuals who have atrophic gastritis (thin and poorly functioning stomach lining), even if they don't have Pernicious Anemia, but are more commonly found when Pernicious Anemia develops. On the other hand, when Anti-Intrinsic Factor antibodies are found, the atrophic gastritis is almost always accompanied by vitamin B12 deficiency.