Important: This page is general information, not medical advice. It does not recommend or prescribe any treatment. Always consult your doctor or pharmacist before starting, stopping or changing any medicine.
About Immune System and Disorders
Your immune system is a complex network of cells, tissues, and organs. Together they help the body fight infections and other diseases.
When germs such as bacteria or viruses invade your body, they attack and multiply. This is called an infection. The infection causes the disease that makes you sick. Your immune system protects you from the disease by fighting off the germs.
The immune system has many different parts, including:
- Your skin, which can help prevent germs from getting into the body
- Mucous membranes, which are the moist, inner linings of some organs and body cavities. They make mucus and other substances which can trap and fight germs.
- White blood cells, which fight germs
- Organs and tissues of the lymph system, such as the thymus, spleen, tonsils, lymph nodes, lymph vessels, and bone marrow. They produce, store, and carry white blood cells.
Your immune system defends your body against substances it sees as harmful or foreign. These substances are called antigens. They may be germs such as bacteria and viruses. They might be chemicals or toxins. They could also be cells that are damaged from things like cancer or sunburn.
When your immune system recognizes an antigen, it attacks it. This is called an immune response. Part of this response is to make antibodies. Antibodies are proteins that work to attack, weaken, and destroy antigens. Your body also makes other cells to fight the antigen.
Afterwards, your immune system remembers the antigen. If it sees the antigen again, it can recognize it. It will quickly send out the right antibodies, so in most cases, you don't get sick. This protection against a certain disease is called immunity.
There are three different types of immunity:
- Innate immunity is the protection that you are born with. It is your body's first line of defense. It includes barriers such as the skin and mucous membranes. They keep harmful substances from entering the body. It also includes some cells and chemicals which can attack foreign substances.
- Active immunity, also called adaptive immunity, develops when you are infected with or vaccinated against a foreign substance. Active immunity is usually long-lasting. For many diseases, it can last your entire life.
- Passive immunity happens when you receive antibodies to a disease instead of making them through your own immune system. For example, newborn babies have antibodies from their mothers. People can also get passive immunity through blood products that contain antibodies. This kind of immunity gives you protection right away. But it only lasts a few weeks or months.
Sometimes a person may have an immune response even though there is no real threat. This can lead to problems such as allergies, asthma, and autoimmune diseases. If you have an autoimmune disease, your immune system attacks healthy cells in your body by mistake.
Other immune system problems happen when your immune system does not work correctly. These problems include immunodeficiency diseases. If you have an immunodeficiency disease, you get sick more often. Your infections may last longer and can be more serious and harder to treat. They are often genetic disorders.
There are other diseases that can affect your immune system. For example, HIV is a virus that harms your immune system by destroying your white blood cells. If HIV is not treated, it can lead to AIDS (acquired immunodeficiency syndrome). People with AIDS have badly damaged immune systems. They get an increasing number of severe illnesses.
It sits within Immune System.
The lead U.S. institute for this subject is the National Institute of Allergy and Infectious Diseases.
When to speak to someone. Reading about a topic cannot tell you whether it applies to you. Speak to a doctor or pharmacist if symptoms are severe, sudden, getting worse, or simply not going away — and seek emergency care immediately for chest pain, breathing difficulty, sudden weakness or confusion, or a serious allergic reaction.
Research on Immune System and Disorders
48,004 studies areregistered for this condition on ClinicalTrials.gov, the U.S. National Library of Medicine's public registry. A selection is below — the links go straight to the registry entry, not to a summary of ours.
What a registered study does and does not mean. Registration means a study exists and has been declared publicly. It says nothing about whether the treatment being tested works, is safe, or is available to you. Many studies find no benefit — that is what research is for. Never seek out an experimental treatment on the strength of a registry entry alone.
Research currently under way
- Targeted Therapy Directed by Genetic Testing in Treating Patients With Advanced Refractory Solid Tumors, Lymphomas, or Multiple Myeloma (The MATCH Screening Trial)National Cancer Institute (NCI)
- A Phase 2 Master Protocol Assessing Inebilizumab and Blinatumomab in Autoimmune DiseasesAmgen
- Longitudinal Immunophenotyping of Patients With Inflammatory Bowel DiseaseNational Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
- Pre-transplant Purging and Post-transplant MRD-guided Maintenance Therapy With Elranatamab in Patients With High-risk Multiple MyelomaM.D. Anderson Cancer Center
- A Phase 1 Study of UB-VV500 With Rapamycin in Relapsed/Refractory Multiple MyelomaUmoja Biopharma
- Inotuzumab Ozogamicin in Treating Younger Patients With B-Lymphoblastic Lymphoma or Relapsed or Refractory CD22 Positive B Acute Lymphoblastic LeukemiaChildren's Oncology Group
Research already completed
- Venetoclax in Combination With BEAM Conditioning Regimen for ASCT in Non-Hodgkin LymphomaCase Comprehensive Cancer Center
- Increasing PrEP Use in High-Risk Social Networks of African-American MSM in Underserved Low-Risk CitiesMedical College of Wisconsin
Study data from ClinicalTrials.gov, a service of the U.S. National Library of Medicine. Retrieved 2026-07-30. Registry entries are supplied by study sponsors and investigators; ClinicalTrials.gov does not verify their scientific validity. PocketsInfo is not affiliated with, and not endorsed by, the NLM or the NIH.
Where to read more
Rather than paraphrase, we point you to the primary sources. Every link below is to a government health agency, a national institute or a recognised medical body — grouped by what you are trying to find out.
Symptoms
- 10 Warning Signs of Primary ImmunodeficiencyJeffrey Modell Foundation
Related Issues
- Covid-19 Vaccines for Moderately to Severely Immunocompromised PeopleCenters for Disease Control and Prevention
- Flu Vaccine Guidance for Patients with Immune DeficiencyAmerican Academy of Allergy, Asthma, and Immunology
Genetics
- 22q11.2 deletion syndrome: MedlinePlus GeneticsNational Library of Medicine
- Activated PI3K-delta syndrome: MedlinePlus GeneticsNational Library of Medicine
- Adenosine deaminase deficiency: MedlinePlus GeneticsNational Library of Medicine
- Anhidrotic ectodermal dysplasia with immune deficiency: MedlinePlus GeneticsNational Library of Medicine
- Autosomal dominant hyper-IgE syndrome: MedlinePlus GeneticsNational Library of Medicine
- Bare lymphocyte syndrome type I: MedlinePlus GeneticsNational Library of Medicine
- Bare lymphocyte syndrome type II: MedlinePlus GeneticsNational Library of Medicine
- Chediak-Higashi syndrome: MedlinePlus GeneticsNational Library of Medicine
- Chronic granulomatous disease: MedlinePlus GeneticsNational Library of Medicine
- Common variable immune deficiency: MedlinePlus GeneticsNational Library of Medicine
- Complement component 2 deficiency: MedlinePlus GeneticsNational Library of Medicine
- Complement component 8 deficiency: MedlinePlus GeneticsNational Library of Medicine
- Complement factor I deficiency: MedlinePlus GeneticsNational Library of Medicine
- DOCK8 immunodeficiency syndrome: MedlinePlus GeneticsNational Library of Medicine
- Erdheim-Chester disease: MedlinePlus GeneticsNational Library of Medicine
- Familial candidiasis: MedlinePlus GeneticsNational Library of Medicine
- Familial hemophagocytic lymphohistiocytosis: MedlinePlus GeneticsNational Library of Medicine
Clinical Trials
- ClinicalTrials.gov: Granulomatous Disease, ChronicNational Institutes of Health
- ClinicalTrials.gov: Immune System DiseasesNational Institutes of Health
- ClinicalTrials.gov: Primary Immunodeficiency DiseasesNational Institutes of Health
- ClinicalTrials.gov: Severe Combined ImmunodeficiencyNational Institutes of Health
Medical subject headings
Clinicians and researchers index this subject under Immune System Diseases, Immune System. These are the terms to use when searching medical literature.
This page is built from the MedlinePlus health topic record for Immune System and Disorders, a service of the U.S. National Library of Medicine (NLM), National Institutes of Health. Information is from MedlinePlus.gov. PocketsInfo is not affiliated with, and is not endorsed by, the NLM or the NIH. Retrieved 30 July 2026.