[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Immunology](https://durgical.com/en/immunology/) › [Lymphoid organs](https://durgical.com/en/immunology/#a-organs) › Mucosa-associated lymphoid tissue (tonsils, Peyer patches) [Immunology](https://durgical.com/en/immunology/) · [Lymphoid organs](https://durgical.com/en/immunology/#a-organs) # Mucosa-associated lymphoid tissue (tonsils, Peyer patches) - Organ Lymphoid tissue under the mucosa of the throat, gut and airways samples what we swallow and breathe and answers mainly with IgA. Updated 2026-11-01 **See it in 3D:** [Palatine tonsils](https://durgical.com/en/anatomy/palatine-tonsil/) · [Ileum](https://durgical.com/en/anatomy/ileum/) · [Appendix](https://durgical.com/en/anatomy/vermiform-appendix/) ## Key points - The pharyngeal ring of tonsils: palatine, pharyngeal (adenoid), lingual and tubal tonsils. - Peyer patches are in the lamina propria and submucosa of the ileum. - M cells in the epithelium over Peyer patches carry antigens from the gut lumen to the follicles below. - MALT B cells switch mainly to IgA, which is secreted across the epithelium as dimeric secretory IgA. - Chronic H. pylori gastritis can drive a MALT lymphoma of the stomach. ## What it is Mucosa-associated lymphoid tissue (MALT) is the collection of lymphoid follicles that sit under mucous membranes, without a full capsule. It includes the tonsils of the pharynx, the Peyer patches of the small intestine (mostly the ileum), lymphoid tissue in the appendix and bronchus-associated tissue. It guards the largest surface the body exposes to the outside and is the main source of secretory IgA. ## Structure - Unencapsulated lymphoid follicles, often with germinal centers, beneath a mucosal epithelium. - Palatine tonsils: stratified squamous epithelium that dips into deep crypts that trap material. - Pharyngeal tonsil (adenoid): on the roof and back wall of the nasopharynx, covered by respiratory epithelium. - Peyer patches: dome-shaped follicle groups under a specialized epithelium with M cells. ## Function - Samples food, inhaled particles and microbes and starts local responses. - Produces secretory IgA, which binds microbes and toxins at the surface without causing inflammation. - Helps keep tolerance to food and normal gut flora. ## Clinical notes - Tonsillitis and streptococcal pharyngitis; peritonsillar abscess as a complication. - Enlarged adenoids in children: mouth breathing, snoring, sleep apnea and middle-ear problems. - Lymphoid hyperplasia in the appendix can block its lumen and trigger appendicitis in young people. - Crohn disease often starts in the terminal ileum, where Peyer patches are richest. - Selective IgA deficiency, the most common primary antibody defect, leads to mucosal infections in some people. ## Memory aid MALT is the customs office at every border crossing: M cells inspect the luggage, the follicle decides, and IgA is the polite stamp that sends trouble back without a fight. ## Test yourself Think of the answer, then tap the question to see it. ## Where are Peyer patches found? In the lamina propria and submucosa of the small intestine, mostly the ileum. ## What do M cells do? They take up antigens from the gut lumen and deliver them to the lymphoid follicles beneath the epithelium. ## Which antibody class does MALT mainly produce? IgA, secreted across the mucosa as secretory IgA. ## Which tonsil becomes the adenoid when enlarged? The pharyngeal tonsil, on the roof and back wall of the nasopharynx. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/immunology/mucosa-associated-lymphoid-tissue/) ## See it in 3D The structures of Durgical's 3D anatomy where it is found. - [Palatine tonsils](https://durgical.com/en/anatomy/palatine-tonsil/) - [Ileum](https://durgical.com/en/anatomy/ileum/) - [Appendix](https://durgical.com/en/anatomy/vermiform-appendix/) ## Related - [Primary and secondary lymphoid organs](https://durgical.com/en/immunology/primary-and-secondary-lymphoid-organs/) - [Lymph node: cortex, paracortex, medulla](https://durgical.com/en/immunology/lymph-node-cortex-paracortex-medulla/) - [B cell and plasma cell](https://durgical.com/en/immunology/b-cell-and-plasma-cell/) - [Antibody structure and isotypes (IgG, IgA, IgM, IgE, IgD)](https://durgical.com/en/immunology/antibody-structure-and-isotypes/) ## Related conditions - [Streptococcal pharyngitis](https://durgical.com/en/conditions/streptococcal-pharyngitis/) - [Peritonsillar abscess](https://durgical.com/en/conditions/peritonsillar-abscess/) - [Coeliac disease](https://durgical.com/en/conditions/coeliac-disease/) - [Crohn disease](https://durgical.com/en/conditions/crohn-disease/) - [Acute appendicitis](https://durgical.com/en/conditions/acute-appendicitis/) [← All of immunology](https://durgical.com/en/immunology/) Educational content on the immune system; not a treatment or individual vaccination guide and no substitute for a health professional's advice. No doses are given. Sources: [21.1 Anatomy of the Lymphatic and Immune Systems](https://openstax.org/books/anatomy-and-physiology-2e/pages/21-1-anatomy-of-the-lymphatic-and-immune-systems) (OpenStax, Rice University (Anatomy and Physiology 2e), 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 (Anatomy and Physiology 2e), 2022). ## **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/immunology/mucosa-associated-lymphoid-tissue/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/immunology/mucosa-associated-lymphoid-tissue/