[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Physiology](https://durgical.com/en/physiology/) › [Blood, hemostasis and basic immunity](https://durgical.com/en/physiology/#s-blood) › Innate and adaptive immunity: overview [Physiology](https://durgical.com/en/physiology/) · [Blood, hemostasis and basic immunity](https://durgical.com/en/physiology/#s-blood) # Innate and adaptive immunity: overview - Concept - Exam priority: medium The body has a fast, general defence (innate) and a slower, precise one with memory (adaptive). They work as a team. Updated 2026-11-01 Also called: Immune system basics **See it in 3D:** [Thymus](https://durgical.com/en/anatomy/thymus/) · [Spleen](https://durgical.com/en/anatomy/spleen/) · [Hip bone](https://durgical.com/en/anatomy/hip-bone/) · [Palatine tonsils](https://durgical.com/en/anatomy/palatine-tonsil/) ## Key points - Innate: no memory, germline pattern receptors (Toll-like receptors); adaptive: memory, receptors rearranged in each lymphocyte. - Dendritic cells link the two: they capture antigen in tissue and present it to T cells in lymph nodes. - MHC I (all nucleated cells) presents to CD8⁺ cytotoxic T cells; MHC II (antigen-presenting cells) presents to CD4⁺ helper T cells. - Primary response is mostly IgM; the secondary (memory) response is faster and mainly IgG; this is the basis of vaccination. ## What it is Innate immunity (barriers, phagocytes, complement, NK cells) acts within minutes and recognizes patterns shared by many microbes. Adaptive immunity (B and T lymphocytes) takes days on first contact, recognizes specific antigens and leaves memory, so a second exposure is faster and stronger. This page is a physiology overview; DurgiPedia's Immunology section covers the details. ## Key facts - Passive immunity: maternal IgG crosses the placenta and IgA arrives in breast milk, protecting infants for months. - HIV infects CD4⁺ T cells, the coordinators of both antibody and cellular responses, which explains opportunistic infections. ## The two arms | Feature | Innate | Adaptive | | --- | --- | --- | | Speed | Minutes to hours | Days (first time); faster with memory | | Recognition | Shared microbial patterns | Specific antigens | | Memory | No | Yes | | Main components | Skin and mucosa, neutrophils, macrophages, NK cells, complement | B cells and antibodies, CD4⁺ and CD8⁺ T cells | ## Test yourself Think of the answer, then tap the question to see it. ## Why is the second exposure to an antigen met with a faster, stronger antibody response? The first response leaves memory B and T cells, and B cells have switched class and matured in affinity; on re-exposure they activate quickly and make mainly high-affinity IgG. ## Which T cells recognize a virus-infected liver cell and through which molecule? CD8⁺ cytotoxic T cells, which recognize viral peptides on MHC class I, present on all nucleated cells. ## How do innate cells 'know' that a microbe is foreign without prior exposure? Pattern receptors such as Toll-like receptors, encoded in the germline, bind molecules shared by microbes but absent from human cells, like lipopolysaccharide or bacterial flagellin. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/physiology/innate-and-adaptive-immunity-overview/) ## See it in 3D The structures of Durgical's 3D anatomy where it happens. - [Thymus](https://durgical.com/en/anatomy/thymus/) - [Spleen](https://durgical.com/en/anatomy/spleen/) - [Hip bone](https://durgical.com/en/anatomy/hip-bone/) - [Palatine tonsils](https://durgical.com/en/anatomy/palatine-tonsil/) ## Related topics - [White blood cells: types and functions](https://durgical.com/en/physiology/white-blood-cells-types-and-functions/) - [The physiology of inflammation](https://durgical.com/en/physiology/the-physiology-of-inflammation/) - [Blood groups, transfusion and transfusion reactions](https://durgical.com/en/physiology/blood-groups-transfusion-and-transfusion-reactions/) - [Rh incompatibility](https://durgical.com/en/physiology/rh-incompatibility/) ## Related conditions - [HIV infection and AIDS](https://durgical.com/en/conditions/hiv-infection-and-aids/) - [Anaphylaxis](https://durgical.com/en/conditions/anaphylaxis/) ## In Biochemistry - [Immunoglobulins (antibodies)](https://durgical.com/en/biochemistry/enzymes/immunoglobulins/) [← All of physiology](https://durgical.com/en/physiology/) Educational physiology content; not a diagnostic or treatment guide and no substitute for a health professional's advice. Values are approximate references. No doses are given. Sources: [21.2 Barrier Defenses and the Innate Immune Response](https://openstax.org/books/anatomy-and-physiology-2e/pages/21-2-barrier-defenses-and-the-innate-immune-response) (OpenStax (Rice University), 2022); [21.3 The Adaptive Immune Response: T lymphocytes and Their Functional Types](https://openstax.org/books/anatomy-and-physiology-2e/pages/21-3-the-adaptive-immune-response-t-lymphocytes-and-their-functional-types) (OpenStax (Rice University), 2022); [21.4 The Adaptive Immune Response: B-lymphocytes and Antibodies](https://openstax.org/books/anatomy-and-physiology-2e/pages/21-4-the-adaptive-immune-response-b-lymphocytes-and-antibodies) (OpenStax (Rice University), 2022); Hall JE. Guyton and Hall Textbook of Medical Physiology, 13th ed. (ch. 35). Reference book used to check facts; its text and figures are not reproduced (Elsevier, 2016). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/physiology/innate-and-adaptive-immunity-overview/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/physiology/innate-and-adaptive-immunity-overview/