Summary
The body's defence network of cells, tissues and molecules that protects against pathogens.
In depth
Organs: bone marrow, thymus, spleen, lymph nodes and mucosal tissues. Layers of defence: physical and chemical barriers, innate immunity, then adaptive immunity. The system must tell self from non-self, tolerate harmless things and avoid attacking the body.
Failures cause infection, cancer, allergy or autoimmunity.
Immune cells arise from haematopoietic stem cells in bone marrow. Primary lymphoid organs (marrow, thymus) produce and educate cells; secondary organs (nodes, spleen) are where responses start.
Key idea: the system balances strong defence against self-damage.
Frequently asked questions
What is Immune System?
The body's defence network of cells, tissues and molecules that protects against pathogens.
Which area of biology covers Immune System, and how advanced is it?
Immune System is one of the 52 topics in Immunology & Disease. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Adaptive Immunity, Innate Immunity, Immunological Tolerance.
Can you give an example of Immune System?
The thymus educates T cells and shrinks after puberty.
What should I learn before Immune System?
Immune System is a Beginner topic, so no earlier topic is required. Other Beginner topics in Immunology & Disease that pair well with it include Viruses, Innate Immunity, Adaptive Immunity.
What topics are related to Immune System?
The closest topics to Immune System are Adaptive Immunity, Innate Immunity, Immunological Tolerance, Innate Lymphoid Cells. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Immune System?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Immune System. To practise the whole of Immunology & Disease, use the Immunology & Disease quiz.
How is Immune System different from Adaptive Immunity?
Immune System: The body's defence network of cells, tissues and molecules that protects against pathogens. Adaptive Immunity: Slower, specific defence involving lymphocytes that remember pathogens. Read both side by side and note what each one explains.
How should I study Immune System step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Adaptive Immunity and explain the difference aloud. Finally, take the Immunology & Disease quiz and come back to this page for any question you miss.