Medical disclaimer: This page is general health information for education only. It is not medical advice and is not a substitute for diagnosis or treatment by a qualified health professional. It has not been reviewed by a clinician. In an emergency, call 911 or your local emergency number.
Many parts working together
The immune system includes cells, tissues and organs that help defend the body against infection. Skin and mucous membranes form barriers. White blood cells and the lymphatic system contribute to detecting and responding to threats. MedlinePlus on the immune system covers its parts and disorders.
Different kinds of protection
Innate immunity is protection present from birth. Adaptive immunity develops through encounters with an infection or vaccination. Passive immunity comes from antibodies made elsewhere, such as antibodies passed from a mother to a baby. See MedlinePlus on the immune response.
When responses go wrong
An immune response can be misdirected, excessive or insufficient. Allergies, autoimmune diseases and immunodeficiency are different kinds of problems; the terms are not interchangeable.
Questions to bring
- What does this test tell us about my immune system?
- Does my medical history change which vaccines or precautions I need?
- Could a medicine I take affect my immune response?
Do not change a prescribed medicine based on a general description of immunity. Ask the professional managing your care about your own circumstances.
See all condition guides, use our appointment preparation guide, or read our guide to allergic rhinitis.
Sources & further reading
Sources consulted September 20, 2026. This is a drafting date, not a medical review date.