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| | 免疫器官は魚の種類によって異なる。無顎類は[[pronephros/ja|前腎]]内に[[lymphoid tissue/ja|リンパ組織]]をもち、腸に[[granulocyte/ja|顆粒球]]をもつ。彼らは[[Adaptive immunity in jawless fish/ja|独自の獲得免疫系]]をもち、[[variable lymphocyte receptor/ja|可変リンパ球受容体]]（VLR）を利用して広範な抗原に対する免疫を生成する。その結果は有顎類魚類や四肢動物とよく似ているが、[[Convergent evolution/ja|収斂進化]]により独自に進化した可能性がある。すべての有顎類魚類はB細胞とT細胞にそれぞれ[[immunoglobulin/ja|免疫グロブリン]]と[[T cell receptor/ja|T細胞受容体]]を備えた[[adaptive immune system/ja|獲得免疫系]]をもつ。これは[[V(D)J recombination/ja|V(D)J再構成]]を利用して広範な抗原に対する免疫を作り出す。このシステムは一度進化し、有顎脊椎動物のクレードの基盤となった。軟骨魚類は3つの特殊な免疫器官をもち、それぞれ生殖腺の周囲にあるエピゴナル器官、食道内の[[Leydig's organ/ja|ライディッヒ器官]]、腸内の[[spiral valve/ja|螺旋弁]]であり、彼らの[[thymus/ja|胸腺]]と[[spleen/ja|脾臓]]は四肢動物の免疫系における同じ器官と類似の機能をもつ。硬骨魚類は胸腺にリンパ球をもち、脾臓や他の器官に他の免疫細胞をもつ。 |
| Immune organs vary by type of fish. The jawless fish have [[lymphoid tissue]] within the [[pronephros|anterior kidney]], and [[granulocyte]]s in the gut. They have [[Adaptive immunity in jawless fish|their own type of adaptive immune system]]; it makes use of [[variable lymphocyte receptor]]s (VLR) to generate immunity to a wide range of antigens, The result is much like that of jawed fishes and tetrapods, but it may have [[Convergent evolution|evolved separately]]. All jawed fishes have an [[adaptive immune system]] with B and T [[lymphocytes]] bearing [[immunoglobulin]]s and [[T cell receptor]]s respectively. This makes use of [[V(D)J recombination|Variable–Diversity–Joining rearrangement]] (V(D)J) to create immunity to a wide range of antigens. This system evolved once and is basal to the jawed vertebrate clade. Cartilaginous fish have three specialized organs that contain immune system cells: the epigonal organs around the gonads, [[Leydig's organ]] within the esophagus, and a [[spiral valve]] in their intestine, while their [[thymus]] and [[spleen]] have similar functions to those of the same organs in the immune systems of tetrapods. Teleosts have lymphocytes in the thymus, and other immune cells in the spleen and other organs.
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