Summary
Rapid, non-specific defences such as skin, mucus, phagocytes and inflammation.
In depth
Barriers: skin, mucus, cilia, stomach acid, lysozyme and the normal flora. Cells: neutrophils, macrophages, dendritic cells, NK cells. Responses start within minutes to hours and are not antigen-specific, with no lasting memory (though trained immunity is being studied).
Pattern recognition receptors detect microbial molecules.
Innate responses begin with recognition of conserved microbial patterns (PAMPs). Barriers are the first line; phagocytes and complement the second. Innate signals also instruct adaptive immunity.
Example: stomach acid kills most ingested microbes.
Innate responses begin within minutes and use pattern recognition receptors (TLRs, NOD-like and RIG-I) that detect PAMPs (molecular patterns of microbes) and DAMPs (signs of damage). They trigger inflammation, interferon release, phagocytosis and complement. Defensins and other antimicrobial peptides punch holes in membranes.
Innate responses are not specific and have no classic memory, though trained immunity (epigenetic reprogramming of monocytes, for instance after BCG vaccination) gives some enhanced responses. They also instruct adaptive immunity, since dendritic cells present antigen and give co-stimulatory signals.
Remember: the innate system is the first line, being fast and broad, while the adaptive system is slower but precise.
Frequently asked questions
What is Innate Immunity?
Rapid, non-specific defences such as skin, mucus, phagocytes and inflammation.
Which area of biology covers Innate Immunity, and how advanced is it?
Innate Immunity 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, Complement System, Toll-Like Receptors.
Can you give an example of Innate Immunity?
Tears contain lysozyme that digests bacterial walls.
What should I learn before Innate Immunity?
Innate Immunity is a Beginner topic, so no earlier topic is required. Other Beginner topics in Immunology & Disease that pair well with it include Immune System, Viruses, Adaptive Immunity.
What topics are related to Innate Immunity?
The closest topics to Innate Immunity are Adaptive Immunity, Complement System, Toll-Like Receptors, Immune System. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Innate Immunity?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Innate Immunity. To practise the whole of Immunology & Disease, use the Immunology & Disease quiz.
How is Innate Immunity different from Adaptive Immunity?
Innate Immunity: Rapid, non-specific defences such as skin, mucus, phagocytes and inflammation. 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 Innate Immunity 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.