Immunology L2_Organs Lecture Notes PDF

Immunology Lecture 2 Organs and Cells of the immune system  1. Organs Of the Immune System  Primary Lymphoid Organs: where lymphocytes develop/mature o Bone Marrow and Thymus : Maturation Site  Secondary Lymphoid Organs : where mature lymphocytes and antigen presenting cells interac...

Immunology Lecture 2 Organs and Cells of the immune system  1. Organs Of the Immune System  Primary Lymphoid Organs: where lymphocytes develop/mature o Bone Marrow and Thymus : Maturation Site  Secondary Lymphoid Organs : where mature lymphocytes and antigen presenting cells interact to initiate a specific immune response o Spleen o Lymph nodes o GALT (gut associated lymph tissue):Tonsils – Peyer’s Patches – Appendix o MALT (mucosal associated lymph tissue) o BALT (bronchial associated lymph tissue — Trap antigen, APC, Lymphocyte Proliferation The Lymphatic System Lymph, lymphatic vessels, lymphoid tissue, and red bone marrow Contains lymphocytes and phagocytic cells Lymph carries microbes to lymph nodes where lymphocytes and macrophages destroy the pathogen The Lymphatic System Right Thoracic (left lymphatic duct lymphatic) duct Tonsil Right Left subclavian subclavian vein vein Thymus Lymph node Thoracic duct Spleen Large intestine Small intestine Peyer’s patch Lymphatic vessel Red bone marrow Lymphatic Vessels Microscopic blind-ended vessels in capillary beds of tissues Absorb excess extracellular fluid = The lymph Lymph in lymphatic capillary Lymphatic capillary One-way opening Interstitial fluid flow Tissue cells Lymphatic vessel Toward lymph node Lymphatic capillaries and lymphatic vein Lymphatic Vessels The lymph: Watery, Plasma-like fluid which contains WBCs that anatomically communicate with the vessels of the cardiovascular system Interstitial fluid (between cells) Venule Tissue cell Lymph in lymphatic Arteriole capillary Lymphatic capillary Blood capillary Flow of fluid between arteriole, blood capillaries, lymphatic capillaries, and venule  Drainage of Lymph Capillaries Lymph Large lymphatic vessels The cardiovascular system Thoracic duct (left subclavian vein) Right lymphatic duct (right subclavian vein) Lymphoid (Lymphatic) Tissue Framework of loose connective tissue with accumulations of lymphocytes Plays a major role in defense against microbes Two basic types Diffuse: unorganized collections of lymphocytes Nodular: more organized (see Lymphatic Nodules) Found at sites of portals of entry In connective tissue of mucous membranes in gastrointestinal, respiratory, urinary, and reproductive tracts Lymphatic Nodules Oval-shaped concentrations of lymphoid tissue Not surrounded by connective tissue capsule Referred as Mucosa-associated lymphoid tissue (MALT) In MALT, lymphocytes are densely packed within loose connective tissue in the mucous membranes 1. Respiratory tract Bronchial-associated lymphoid tissue (BALT) aggregates of secondary lymphoid tissue line the respiratory epithelium. 2. Gastrointestinal tract Gut-associated lymphoid tissues (GALT) 3. Urinary tract 4. Reproductive tract Lymphatic Nodules Mucosa-associated lymphoid tissue (MALT) Lymphatic Nodules Gut-associated lymphoid tissues (GALT) include: Tonsils, adenoids, appendix and Peyer’s patches (which line the small intestine) M cells Nature Immunology in collaboration with Arkitek Studios have produced an amazing animation unravelling the complexities of mucosal immunology in health and disease https://youtu.be/gnZEge78_78 Lymphatic Nodules MALT have similar anatomy and function to lymph nodes Trap pathogens & activate lymphocytes Pathogens arrive at MALT by direct delivery across the mucosa, via specialized M cells at Peyer’s patches Lymphocytes get activated and start an immune response Tonsils Located in the wall of the pharynx Remove foreign substances entering the body by ingestion or inhalation Embedded in mucous membranes Single pharyngeal tonsil (adenoid) Pair of palatine tonsils Pair of lingual tonsils Lymph Nodes Approximately 600 are located along the lymphatic vessels Surrounded by a connective tissue capsule Afferent lymphatic vessels: lymph enters the node Efferent lymphatic: lymph exits Lymph is filtered in lymph nodes Phagocytosis, B and T lymphocytes Lymph Nodes (Cont.) Spleen Largest lymphatic organ Contains 25% of the body’s lymphocytes Filters blood and lymph In response to circulating antibodies, macrophages, B and T lymphocytes are activated to eliminate pathogens Thymus Gland Bilobed organ in the mediastinum Produces thymosins: stimulate the maturation of T lymphocytes Essential in the development of the immune system in the infant Large after birth, capacity slows down during puberty and slow atrophy thereafter