Indima Ye-Thymus Gland Esimiso Sokuzivikela Emzimbeni
I-thymus gland iyisitho esibalulekile ohlelweni lokuzivikela komzimba lomuntu, yize ngokuvamile ingaziwa kakhulu kunezinye izitho ezifana ne-spleen noma i-bone marrow. I-thymus idlala indima ebalulekile ekwakheni nasekunakekeleni amangqamuzana omzimba, okwenza akwazi ukuvikela umzimba ekuthelelekeni ngaphandle kokuhlasela izicubu zawo. Ukuqonda i-thymus kusisiza siqonde ukuthi izivikelo zomzimba zikhula kanjani kusukela ebuntwaneni, ukuthi kungani izivikelo zomzimba zishintsha ngokuguga, nokuthi kwenzekani lapho ukusebenza kwe-thymus kuphazamiseka.
Indawo kanye nezici ze-thymus gland
I-thymus itholakala engxenyeni engenhla yesifuba, ngemuva nje kwethambo lesifuba (sternum) naphambi kwenhliziyo. Ezinganeni, inkulu futhi iyasebenza. Kodwa-ke, njengoba ikhula, i-thymus idlula enkambisweni ebizwa ngokuthi i-involution, ehilela ukuncipha nokufaka esikhundleni sezinye zezicubu zayo ezisebenzayo ngamafutha. Naphezu kokuncipha kwayo, i-thymus igcina indima yayo yokuzivikela, ikakhulukazi ngokuzuza amaseli e-T akhiqizwa esemncane.
Ngokwe-anatomic, i-thymus yakhiwe ama-lobes amabili futhi ihlukaniswe ezindaweni ezimbili eziyinhloko: i-cortex (ingxenye engaphandle) kanye ne-medulla (ingxenye engaphakathi). I-cortex icebile ngamaseli e-T asemasha akhulayo (ama-thymocyte), kuyilapho i-medulla iqukethe amaseli e-T avuthiwe kanye nezakhiwo ezibizwa ngokuthi ama-corpuscle kaHassall, okucatshangwa ukuthi ahilelekile ekuvuthweni nasekulawulweni kwezimpendulo zomzimba.
I-thymus njenge-"school" yamaseli e-T
Indima eyinhloko ye-thymus ukusebenza njengendawo yokuvuthwa kwama-T lymphocyte (amaseli e-T), enye yezingxenye ezibaluleke kakhulu zesistimu yokuzivikela yomzimba eguquguqukayo. Amaseli e-T avela kumaseli okuqala emnkantsheni wamathambo bese ethutha aye ku-thymus ukuze akhule. Ku-thymus, lawa maseli adlula ochungechungeni lwezinqubo zokukhetha ezinzima ukuqinisekisa ikhono lawo loku:
1. Ukuqaphela ama-antigen angaphandle (isib. amagciwane namabhaktheriya) ngendlela efanele.
2. Ayihlaseli izicubu zomzimba (ivimbela ukuzivikela komzimba).
Le nqubo ivame ukufana nenqubo yemfundo nokukhetha eqinile, njengesikole samasosha noma i-academy ekhethekile, ngoba amangqamuzana kuphela ahlangabezana nezindinganiso azo "phothula" futhi athunyelwe ekujikelezeni kwegazi nakwezinye izitho ze-lymphoid.
Ukukhetha okuhle: ukuqinisekisa ukuthi amaseli e-T angasebenza
Isinyathelo sokuqala esibalulekile ukukhetha okuhle. Kulesi sinyathelo, i-thymus ihlola ukuthi i-T-cell receptor (TCR) iyakwazi yini ukubona ama-molecule e-MHC (i-major histocompatibility complex), "amapulatifomu" ebusweni bamaseli omzimba asetshenziselwa ukubonisa izingcezu ze-antigen. Uma iseli le-T lingakwazi ukubona i-MHC nhlobo, libhekwa njengelingenamsebenzi ekuzivikeleni komzimba futhi liyasuswa.
Imiphumela yokukhetha okuhle iyasiza futhi ekunqumeni "umsebenzi" wamaseli e-T: ukuthi angaba yini amaseli e-CD4 T (amaseli e-T awusizo) adlala indima ekulawuleni izimpendulo zomzimba, noma amaseli e-CD8 T (amaseli e-T ayingozi) adlala indima ekubulaleni amaseli atheleleke ngegciwane kanye namaseli omdlavuza.
Ukukhetha okungalungile: ukuvimbela ukuzivikela komzimba
Ngemva kokudlula ekukhetheni okuhle, amaseli e-T abe esedlula ekukhetheni okubi. Lesi sigaba sihlose ukuqeda amaseli e-T aqaphela ama-self-antigens kakhulu. Uma amaseli e-T ebopha kakhulu kuma-antigen omzimba, angahlasela izitho zomzimba futhi abangele izifo zokuzivikela komzimba. I-thymus izobangela ukufa okuhleliwe (i-apoptosis) kwala maseli e-T ayingozi.
Indlela eyodwa ebalulekile yokukhetha okungalungile ihilela iphrotheni ye-AIRE (autoimmune regulator). I-AIRE ivumela amangqamuzana athile ku-thymus ukuthi abonise izinhlobo ezahlukene zama-antigen avame ukuba khona ezithweni ezithile kuphela (isb., ama-antigen avela endlaleni ye-thyroid, i-pancreas, noma isikhumba). Ngale ndlela, i-thymus "ingakwazi" ukuletha ama-self-antigen ahlukahlukene kumaseli e-T athuthukayo, ngaleyo ndlela isuse amangqamuzana e-T asabela kula ma-antigen kusenesikhathi.
Ukwakheka kokubekezelelana kwamasosha omzimba kanye nendima yamaseli e-T alawulayo
Ngaphezu kokuqeda amangqamuzana ayingozi, i-thymus isiza futhi ekusunguleni ukubekezelelana kwamasosha omzimba, ikhono lohlelo lokuzivikela komzimba lokubekezelela izicubu zalo. Omunye umphumela obalulekile we-thymus amaseli e-T alawulayo (ama-Tregs). Amaseli e-Treg asebenza "njengebhuleki" ohlelweni lokuzivikela komzimba ukuvimbela ukusabela ngokweqile nokuzibhubhisa. Ama-Tregs asiza ukugcina ibhalansi, ukunciphisa ukuvuvukala okungadingekile, nokuvimbela izifo zokuzivikela komzimba.
Ngamanye amazwi, i-thymus ayikhiqizi nje kuphela amangqamuzana empi, kodwa futhi ikhiqiza amangqamuzana okugcina ukuthula avimbela amasosha omzimba ukuba asebenze ngobudlova ngaphandle kokulawula.
Ubudlelwano be-thymus nokuzivikela komzimba ebuntwaneni
Ngesikhathi sobuntwana kanye nobuntwana, i-thymus iyasebenza kakhulu ekukhiqizeni amaseli amasha e-T. Lokhu kubalulekile ngoba izingane zidinga uhlu olubanzi lwamaseli e-T ukuze zibone izinhlobo ezahlukene zezifo ezihlangana nazo okokuqala. Ukuzivikela okuzivumelanisa nezimo kukhula ngokushesha phakathi nalesi sigaba, njengoba umzimba "uqoqa ulwazi" ngezinhlobo eziningi zama-antigen endawo, ngokutheleleka kwemvelo kanye nokugoma.
Ukusebenza okuphezulu kwe-thymus ngesikhathi sobusha kuchaza nokuthi kungani amasosha omzimba ezingane engaqhubeka nokuthuthukisa uhla oluhlukahlukene lwamaseli e-T. Lokhu kuhlukahluka kunikeza ifa elibalulekile ekubhekaneni nosongo lokutheleleka kamuva ekuphileni.
Ukuguquka kwe-Thymic kanye nezinguquko zomzimba ekugugeni
Njengoba ubusha kanye nobudala busondela, i-thymus iqala ukuncipha, futhi ukukhiqizwa kwamaseli e-T amasha kwehla. Le nqubo yokuguquka ingenye yezinto ezibangela ukuthi amasosha omzimba kubantu abadala asebekhulile angasabeli kahle ezifweni ezintsha. Abantu asebekhulile bavame ukuthembela kumaseli enkumbulo asevele enziwe, kodwa ikhono labo lokwakha amaseli e-T amasha, "amasha" liyehla.
Ngenxa yalokho, abantu abadala basengozini enkulu yezifo ezithile ezithelelanayo, impendulo yabo emithini yokugoma ingase ibe buthaka, futhi inqubo yabo yokululama ingase ihambe kancane. Kodwa-ke, isimiso somzimba sokuzivikela asiyeki ukusebenza; simane siyashintsha, sinamangqamuzana enkumbulo amaningi kanye nokwehla kokuhlukahluka kwamaseli e-T.
Umphumela wokungasebenzi kahle kwe-thymus
Uma i-thymus ingakhuli kahle noma yonakele, imiphumela ingaba mibi kakhulu. Ezinye izimo zezokwelapha ezihlobene ne-thymus zifaka:
1. I-DiGeorge syndrome: isifo sokuzalwa esingabangela ukuthi i-thymus ingakheki kahle, okwenza ingane ibhekane nokuntuleka kwamaseli e-T futhi isengozini yokutheleleka.
2. I-Myasthenia gravis: isifo sokuzivikela komzimba esivame ukuhlotshaniswa ne-thymus ekhulisiwe (hyperplasia) noma isimila se-thymic (thymoma). Nakuba izindlela ziyinkimbinkimbi, kucatshangwa ukuthi i-thymus idlala indima ekuthuthukisweni kwempendulo yokuzivikela yomzimba engalungile.
3. I-Thymoma: isimila esiku-thymus esingathinta ukulawulwa kwamasosha omzimba futhi ngezinye izikhathi sihlotshaniswa nokuzivikela komzimba noma ezinye izifo zokuzivikela komzimba.
Ngakolunye uhlangothi, ukususwa kwe-thymus (thymectomy) ezimweni ezithile kungaba usizo, isibonelo kwezinye izimo ze-myasthenia gravis, yize umphumela uncike eminyakeni kanye nesimo sempilo sesiguli.
I-thymus esimweni sesimanje: ucwaningo kanye nemiphumela yezempilo
Ucwaningo lwanamuhla lugxile endleleni yokugcina noma ukubuyisela ukusebenza kwe-thymus, ikakhulukazi maqondana nokuguga kanye nokululama komzimba ngemva kokwelashwa komdlavuza njengokwelashwa ngamakhemikhali. Izindlela eziningana ezifundwayo zifaka phakathi izici zamahomoni, ama-cytokine, kanye nokwelashwa okuvuselelayo. Umgomo uwukuthuthukisa ikhono lomzimba lokukhiqiza amaseli amasha e-T ukuze kube nokusabela okuqinile nokulinganiselayo komzimba.
Ngaphezu kwalokho, ukuqonda ukukhethwa kwamaseli e-T ku-thymus kusiza nasekuthuthukisweni kwezindlela zokwelapha izifo ezizimele kanye nobuchwepheshe be-immunotherapy, okuhlanganisa nemizamo yokuklama amaseli omzimba ukulwa nomdlavuza. Ngenkathi ucwaningo oluningi lusaqhubeka, i-thymus isalokhu igxile ekunakweni ngenxa yomsebenzi wayo oyisisekelo: ukukhiqiza amaseli e-T asebenzayo futhi aphephile.
Isiphetho
I-thymus gland idlala indima ebalulekile ohlelweni lokuzivikela komzimba, ikakhulukazi njengendawo yokuvuthwa nokukhetha kwamaseli e-T. Ngokukhetha okuhle nokubi, i-thymus iqinisekisa ukuthi amaseli e-T ayakwazi ukulwa namagciwane kodwa angahlaseli amaseli omzimba. I-thymus iphinde ifake isandla ekubekezeleleni amasosha omzimba ngokwakhiwa kwamaseli e-T alawulayo. Nakuba incipha ngokuguga, "umnikelo wokuqala" we-thymus ekwakheni i-repertoire yamaseli e-T unemiphumela ehlala isikhathi eside empilweni yomuntu ye-immunological. Ngokuqonda indima ye-thymus, siqaphela ngokwengeziwe ukuthi ukuzivikela komzimba akukona nje ukulwa nezifo, kodwa futhi nokugcina ibhalansi ukuze amasosha omzimba asebenze kahle.
