Antibodies That Cause B12 Deficiency

Getting to the root cause of B12 deficiency is important to treat and resolve the problem. Our previous blog explained how a B12 deficiency can affect vitality and health. In this blog we will look at how antibodies and an autoimmune process can cause a B12 deficiency.

In this blog on antibodies that cause vitamin B12 deficiency, you will learn:

Which antibodies can cause B12 deficiency?
Which diseases involve these antibodies and how common are they?
What is the treatment for antibodies that cause B12 deficiency?

What are Antibodies?

An antibody is a protein made by the body’s immune system. Antibodies are made to fight germs or antigens that the body identifies as harmful. These can be germs and other microorganisms such as bacteria, fungi, parasites, viruses or chemicals. Each antibody type is unique and defends against one specific type of antigen. The body makes different kinds of antibodies to fight germs in different parts of the body and at different stages of an infection.

Autoantibodies

An autoantibody is an antibody produced by the immune system that is directed against the body’s own tissue. The immune system mistakenly targets the body’s own tissue as an antigen. This can damage tissue and is harmful. It is driven by over-reactive immune responses that lead to autoimmune processes and diseases. When autoantibodies are present, they can develop into autoimmune diseases, such as rheumatoid arthritis, Graves disease or many others. Approximately 8% of the US population is affected by autoimmune disease (NIH, 2025).

Which Antibodies can Cause Vitamin B12 Deficiency?

Antibodies against parietal cells
Antibodies against intrinsic factor

What are Parietal Cells?

Parietal cells are found in the stomach lining. They secrete hydrochloric acid (HcL or stomach acid) and intrinsic factor (IF). HcL secreted by parietal cells helps digest food and absorb vitamins and minerals. The intrinsic factor they produce is also needed for vitamin B12 absorption.

Parietal Cell Antibodies (PCAs)

Parietal cell antibodies are autoantibodies that damage the stomach’s parietal cells. This reduces stomach acid needed for digestion and nutrient absorption as well as intrinsic factor needed for vitamin B12 absorption. These antibodies can lead to a B12 deficiency.

Parietal cell antibodies are typically seen in autoimmune conditions, especially those related to stomach issues. They are specifically associated with:

Autoimmune gastritis
Pernicious anemia
Autoimmune thyroid disease: Hashimoto’s thyroiditis or Graves’ disease
Type 1 diabetes
Gastric cancer
Addison’s disease (adrenal insufficiency) and other autoimmune disorders may be associated with PCAs

PCAs may increase with age, even in healthy older people. If PCAs are found in blood tests, B12 levels should be monitored to assess for gastric issues or autoimmune conditions.

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What Causes Anti-Parietal Cell Antibodies (PCAs)?:

Genetic Predisposition to autoimmune diseases increases risk.
Molecular Mimicry: Infections, especially Helicobacter pylori, can look like parietal cell antigens to the immune system and trigger an autoimmune response.
Chronic Gastric Inflammation: A long-standing gastric irritation or H. pylori infection can damage parietal cells leading the immune system to mistakenly target parietal cells.
Certain nutrition issues can trigger an immune response in genetically susceptible people. This may be things like low antioxidants in the diet or processed meats high in nitrates that can create or worsen gastric inflammation. Alcohol, caffeine and gluten are likely to contribute to gastric inflammation which can trigger an immune response.
Autoimmune Gastritis: A chronic inflammatory disease that destroys parietal cells. Common consequences are vitamin B12 deficiency and possibly pernicious anemia.
Weakened immune regulation in older people can increase the likelihood of autoantibodies.

How Prevalent are Parietal Cell Antibodies? (LabPLUS VIM Serology, 2023):

1% of the population under 20 years old test positive for PCAs.
12-15% of the population over 70 years old test positive for PCAs.
The prevalence of PCAs in female patients was 29.7% (Checchi S, 2010).
This progressively increases from 13% in women aged around 20 years old to 42% in those aged 90 years old.
PCAs are seen in 80 – 90% of patients with pernicious anemia.
PCAs are seen in 60% of patients with gastritis.
33% of patients with thyroiditis and Graves disease show positive parietal cell antibodies. In people with autoimmune thyroid disease, the prevalence of PCAs increases with age (Checchi S, 2010).
30% of patients with iron deficiency anemia have positive parietal cell antibodies.

What is Intrinsic Factor? Intrinsic factor is a protein produced by the parietal cells of the stomach. It binds vitamin B12. This allows for B12 absorption in the small intestine. Any disease, damage or resection in the small intestine can cause B12 malabsorption and deficiency. Anti-Intrinsic Factor Antibodies Intrinsic factor antibodies are autoantibodies that are produced by the immune system and target intrinsic factor (IF), needed for B12 absorption. These antibodies can damage B12 absorption, cause possible B12 deficiency and ultimately result in conditions like pernicious anemia. Antibodies to IF may be present in the following conditions:

Pernicious Anemia: Intrinsic factor antibodies are a key factor in pernicious anemia. In this autoimmune condition, the body produces antibodies that target either intrinsic factor or the parietal cells that produce IF. This disrupts the absorption of vitamin B12, leading to a deficiency. Over time, lack of B12 can cause the symptoms of pernicious anemia, like fatigue, weakness and nerve damage.
Autoimmune Gastritis: This inflammation of the stomach lining can reduce intrinsic factor production. Autoimmune gastritis often affects parietal cells directly which indirectly reduces intrinsic factor. This can contribute to vitamin B12 deficiency.
Gastric Cancer: Chronic autoimmune gastritis, which may involve intrinsic factor antibodies, can increase the risk of gastric cancer over time. This is due to prolonged inflammation and damage to the stomach lining.
Other Autoimmune Disorders: Intrinsic factor antibodies may also be present in other autoimmune conditions like Hashimoto’s thyroiditis, Lupus or others.
Vitamin B12 Deficiency: While not a disease in itself, intrinsic factor antibodies can lead to B12 deficiency and its associated symptoms.

What is the Prevalence of IF Antibodies? It is difficult to assess the prevalence of IF antibodies in the general population. It is likely relatively rare in people with healthy B12 levels, but common in people with pernicious anemia or other B12 deficient conditions.

Anti-intrinsic factor antibodies are present in approximately 70-80% of patients with pernicious anemia (Song M, 2021).
Antibodies against intrinsic factor are present in 50-60% of patients with autoimmune gastritis (NHS, 2025).
In other autoimmune conditions (autoimmune thyroid disease, type 1 diabetes), the prevalence of IF antibodies is higher than in the general population.

Treatment for Antibodies that Cause B12 Deficiency: Can These Antibodies be Eliminated? These antibodies are part of a chronic autoimmune process and cause damage to parietal cells or intrinsic factor. Once tissue damage to these cells has occurred, due to the antibodies and the autoimmune process, that tissue damage cannot be reversed. Conventional medicine says that parietal cell or intrinsic factor antibodies cannot be eliminated. In Functional Medicine, we strive to stop the autoimmune process which involves reducing the antibodies. We cannot reverse the tissue damage that has occurred. But we can aim to stop further tissue damage by reducing antibodies and the autoimmune process. This is done through various steps with a particular focus on gut health. We wrote a 4-part blog series about Autoimmunity & the Gut. An Autoimmune Condition involves:

Genetic tendency
Environmental trigger(s)
Leaky gut

To prevent, address and improve an autoimmune condition, gut health must be improved. How Can we Manage, Improve and possibly Reverse an Autoimmune Process or Disease? The steps to stopping autoimmunity in detail can be found in this blog on Autoimmunity & the Gut Part 2. In the case of parietal cell or intrinsic factor antibodies that lead to autoimmunity, treatment involves: Manage symptoms like B12 deficiency. Replace B12 to prevent B12 deficiency symptoms. This involves vitamin B12 shots, by injection (usually into a muscle). Initially weekly B12 shots for 4–8 weeks then maintain with monthly shots. Treat the autoimmunity to improve, stop and reverse the autoimmune process.

Heal the gut
Remove environmental triggers
Improve diet
See this blog for more specific info

It is possible to improve a case of parietal cell or intrinsic factor antibodies. It is a muti-step process with a key focus on improving gut health and removing environmental triggers. ************** If you have B12 deficient symptoms or antibodies to parietal cells or intrinsic factor, then get in touch with us at the Medicine with Heart clinic. We can help you to best optimize B12 levels and manage any autoimmune conditions. *** Follow us for more info on vitamin B12 and B12 deficiency in our next blog! ***

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