25.6
二次リンパ器官
リンパ節、脾臓、粘膜関連リンパ組織（MALT）などの二次リンパ器官は調和して働き、私たちを病気や感染から守ります。
脾臓はリンパ系の重要な臓器で、腹部の左上側にあります。脾臓は赤髄と白髄という 2 つの主要な領域で構成されており、それぞれ異なる機能を持っています。赤髄は血液の濾過において重要な役割を…
脾臓、リンパ節、粘膜関連リンパ組織(MALT)などの二次リンパ器官は、リンパ球が最初に抗原と出会い、活性化する部位です。
最大のリンパ器官である脾臓は、腹腔の左側、横隔膜の下にあります。組織学的には、白と赤の果肉に分けられます。
白い果肉はリンパ球で構成されており、免疫機能の部位です。一方、赤い果肉はマクロファージが豊富で、すり減った赤血球や病原体の破壊に関与しています。
リンパ節は、鼠径部、腋窩部、頸部の体の表面近くに見られる小さな豆の形をした構造です。
リンパ球の活性化に加えて、リンパ節はリンパ液から病原体や細胞の破片を浄化し、それらが血液に入るのを防ぎます。
MALTは体の粘膜全体に分布しており、病原体から保護します。
小腸の遠位部に見られるパイエル板と、咽頭の周りにリンパ組織の輪を形成する扁桃腺は、MALTの2つの注目すべき例です。
View the full transcript and gain access to JoVE Core videos
Q1: What are the main functions of the spleen in the immune system?
The spleen, the largest lymphoid organ, has two distinct regions with different roles. The white pulp houses lymphocytes and is the site of immune function and antibody production. The red pulp filters blood by destroying worn-out red blood cells and pathogens, while also storing platelets and white blood cells essential for clotting and immune responses.
Q2: Where are lymph nodes located and what do they do?
Lymph nodes are small, bean-shaped structures distributed throughout the body in regions like the inguinal, axillary, and cervical areas. They serve as filters that trap and eliminate foreign substances, house immune cells including lymphocytes and macrophages, and cleanse lymph of pathogens and cellular debris before it enters the blood.
Q3: What is mucosa-associated lymphoid tissue and where is it found?
Mucosa-associated lymphoid tissue (MALT) is distributed throughout mucous membranes lining the digestive, respiratory, urinary, and reproductive systems, providing the first line of defense against pathogens. Examples include tonsils in the pharynx, Peyer's patches in the small intestine, and the appendix, which house lymphoid nodules that monitor and respond to potential threats.
Q4: How do secondary lymphoid organs work together to protect the body?
Secondary lymphoid organs are interconnected by lymphatic vessels that facilitate movement of immune cells between organs and tissues. This network enables lymphocytes to encounter antigens, become activated, and launch coordinated immune responses. The spleen, lymph nodes, and MALT work harmoniously to filter pathogens, produce antibodies, and mount defenses against infections.
Q5: What is the role of Peyer's patches in immune defense?
Peyer's patches are lymphoid nodules found in the lining of the small intestine that vigilantly monitor intestinal contents for potential pathogens. When threats are detected, they trigger an immune response by activating lymphocytes. These structures represent a critical component of mucosa-associated lymphoid tissue protecting against pathogens entering through the digestive tract.
Q6: How does the red pulp differ from the white pulp in the spleen?
The red pulp is rich in macrophages and performs blood filtration by purging old or damaged red blood cells and foreign particles like bacteria and viruses. The white pulp consists of lymphocytes and is the site for immune function and antibody production. Together, these regions enable the spleen to filter blood and mount immune responses.
Q7: Why are tonsils considered part of the immune system?
Tonsils are lymphoid nodules located in the pharyngeal region that form a ring of lymphoid tissue around the pharynx. They serve as a protective barrier, trapping and eliminating pathogens that enter via the mouth or throat. As part of mucosa-associated lymphoid tissue, tonsils provide immune surveillance at a major entry point for pathogens.