Immune System Disorders

How the immune system works

The immune system has two arms. The innate system (skin barriers, neutrophils, complement proteins) responds within minutes to anything that looks foreign. The adaptive system (B cells that make antibodies and T cells that kill infected cells) learns to recognize specific germs and remembers them. The system must also stay "tolerant" of your own tissues and of harmless things like food and pollen.

Immune disorders occur when any part of this goes wrong.

Types of immune disorders

Some people have more than one category. For example, primary immunodeficiencies often come with autoimmune problems, because the faulty immune system is also poorly regulated.

Immunodeficiency disorders

Primary immunodeficiency diseases (also called inborn errors of immunity) number more than 450 known genetic conditions. Many are rare, but together they are more common than once thought, and many are diagnosed late. Secondary immunodeficiency is far more common and includes the effects of cancer treatment, organ transplant drugs and long-term steroids.

Autoimmune diseases

There are more than 80 autoimmune diseases, and together they affect several percent of the population. They are more common in women. Some target one organ (thyroid, pancreas, skin); others are systemic, affecting many organs at once.

Allergic disorders

Allergies are the most common immune disorders. They range from mild hay fever to life-threatening anaphylaxis.

Symptoms that suggest an immune disorder

Signs of a weak immune system:

• Infections that are frequent, severe, last unusually long or need IV antibiotics.
• Infections with unusual germs, such as Pneumocystis pneumonia or severe thrush.
• Recurrent deep skin or organ abscesses.
• Poor growth in children, chronic diarrhea.
• A family history of immunodeficiency or early deaths from infection.

Signs of an overactive or misdirected immune system:

• Joint pain and swelling, morning stiffness.
• Persistent rashes, including a facial "butterfly" rash or rashes that worsen in sunlight.
• Unexplained fevers, fatigue and weight loss.
• Dry eyes and mouth, hair loss, mouth ulcers.
• Hives, swelling, wheezing or sneezing after specific triggers.

How immune disorders are diagnosed

The tests depend on which type is suspected:

• Complete blood count with differential: numbers of white cell types.
• Immunoglobulin levels: IgG, IgA, IgM and IgE.
• Vaccine responses: whether you make antibodies after tetanus or pneumococcal vaccines.
• Lymphocyte subsets (flow cytometry): counts of T cells, B cells and NK cells.
• Complement tests.
• HIV test.
• Autoantibody tests: such as ANA, rheumatoid factor, anti-CCP, celiac antibodies, thyroid antibodies.
• Inflammation markers: CRP and ESR.
• Allergy tests: skin prick tests and specific IgE blood tests.
• Genetic testing for suspected inherited immune defects.

Treatment

• Immunodeficiency: preventing and promptly treating infections, immunoglobulin (antibody) replacement every few weeks, preventive antibiotics, appropriate vaccines (avoiding live vaccines in some conditions), and stem cell transplant or gene therapy for the most severe types.
• Autoimmune disease: anti-inflammatory and immune-calming drugs such as hydroxychloroquine, methotrexate and biologic medicines, plus replacing lost hormones (insulin, thyroid hormone).
• Allergy: avoiding triggers, antihistamines, nasal steroid sprays, inhalers, epinephrine auto-injectors, and allergen immunotherapy.
• Immune cancers: chemotherapy, targeted drugs, immunotherapy and stem cell transplant.

Living with an immune disorder

• Keep a record of infections, antibiotics and test results.
• Stay up to date with recommended inactivated vaccines, and ask before any live vaccine.
• Wash hands often and follow food safety advice if your immunity is low.
• Wear a medical alert if you have severe allergies, no spleen or take strong immune-suppressing drugs.
• Many conditions are best managed by a specialist team in immunology, rheumatology or allergy.

Frequently asked questions

What are the main types of immune system disorders?

The main types are immunodeficiency (a weak immune system, either inherited or acquired), autoimmune disease (the immune system attacks your own tissues), allergy and hypersensitivity (overreaction to harmless substances), autoinflammatory disease, and cancers of immune cells such as lymphoma and leukemia.

What is the difference between autoimmune disease and immunodeficiency?

In immunodeficiency, the immune system is too weak to fight infections properly, so infections are frequent or severe. In autoimmune disease, the immune system is active but misdirected, attacking healthy tissues such as joints, skin or the thyroid. Some people have features of both.

What are signs of a weak immune system?

Warning signs include frequent infections such as four or more ear infections or two or more pneumonias in a year, infections that need IV antibiotics, unusual infections, recurrent deep abscesses, persistent thrush, and in children poor growth. Catching ordinary colds a few times a year is normal.

How do doctors test for immune disorders?

They start with a blood count, antibody (immunoglobulin) levels, an HIV test and markers of inflammation. Depending on the suspected problem, they add vaccine response tests, lymphocyte counts, autoantibody tests such as ANA, allergy tests, or genetic testing.

Can immune disorders be cured?

Some can. Severe inherited immunodeficiencies can be cured with a stem cell transplant or gene therapy, and secondary immunodeficiency often improves when the cause is removed. Most autoimmune and allergic disorders are long-term but can be controlled well with treatment.