Isimiso Sokuzivikela Somzimba Wethu Isimangaliso Sendalo

Asikwazi ukuwabona, kodwa akhona. Amaqembu awo ayizigidi asizungeze kuyo yonke indawo, anamathela kithi, enza wonke umzamo wokungena ngaphakathi kithi. Athanda ukufudumala okunomswakama okuwenza akhule okungaphakathi kithi, futhi uma eselapho inani lawo landa ngokushaqisayo. Uma eyekwa nje enganqandwa, ngokushesha imizimba yethu ingabuswa yiwo ngokuphelele. Okuwukuphela kwendlela esinayo yokubhekana nalelibutho elibhubhisayo yimpi, impi engaphakathi kithi. Kufanele kube impi esheshayo newujuqu phakathi kwalabahlaseli abangaziwa abathwala izifo kanye nesimiso sokuzivikela semizimba yethu esinabavikeli abayizigidi eziyizigidi.a Awukho umusa ocelwayo, futhi awukho onikezwayo. Ukuphila kwethu kusengozini. Yithi esinqobayo noma yiwo. Ngokuvamile kunqoba thina. Kodwa asinqobi njalo. Umphumela uxhomeka ekutheni isimiso sokuzivikela komzimba wethu sikulungela ngokushesha nangokuzidela amathambo kangakanani ukulwa.

ISIMISO sokuzivikela komzimba singesinye sezici ezimangalisayo neziyinkimbinkimbi kakhulu zemizimba yethu eyenziwe ngendlela esabekayo nemangalisayo. Siqhathaniseka kahle nesitho esiyinkimbinkimbi kakhulu kunazo zonke, ubuchopho bomuntu. UWilliam Paul oyisazi sesayensi yesimiso sokuzivikela komzimba seziNhlangano Zesizwe Zezempilo uthi: “Isimiso sokuzivikela komzimba sinekhono eliphawulekayo lokusebenzelana nokwaziswa, lokufunda nokukhumbula, lokwakha nokugcina kanye nokusebenzisa ukwaziswa.” Udumo oluphakeme, kodwa olungaphakeme kakhulu. UDkt. Stephen Sherwin, umqondisi wokucwaninga kwezokwelapha eGenentech, Inc., unezela amazwi akhe okutusa: “Isimiso esiyisimangaliso. Siyawabona amamolecule angakaze abe semzimbeni ngaphambili. Singahlukanisa phakathi kwalokho okungokwalapho nokungekhona.” Futhi uma kungekhona, kusuka impi!

Isimiso sokuzivikela komzimba wethu sikwazi kanjani lokho okungokwalapho nokungekhona? Imolecule ekhethekile yeprotein, ebizwa ngokuthi iMHC (major histocompatibility complex), ihlala ngaphandle kuwo wonke amangqamuzana omzimba wethu. Uphawu lokubona olutshela isimiso sokuzivikela komzimba ukuthi lengqamuzana ingumngane, iyingxenye yethu, ibalulekile kithi. Khona-ke isimiso sokuzivikela komzimba sibona amangqamuzana ethu siqu futhi siwamukele kodwa sihlasela noma imaphi amangqamuzana aveza amamolecule ahlukile—futhi wonke amangqamuzana angewona awethu aveza amamolecule ahlukile kwawethu.

Ngakho isimiso sethu sokuzivikela komzimba sibona ngalamamolecule angaphandle ukuthi ingqamuzana ngayinye “iyithi” noma “iyiwo,” njengento esinayo ngaphakathi noma eyangaphandle. Uma ingeyangaphandle, ibangela ukuba isimiso sethu sokuzivikela komzimba sihlasele. “Umqondo wokuthi isimiso sokuzivikela komzimba kufanele sihlukanise ngokuqhubekayo phakathi kwezinto esinazo ngaphakathi nezivela ngaphandle,” kusho incwadi i-Immunology, “uyisisekelo sayo yonke imfundiso yesayensi yokuzivikela komzimba.” Ohlwini lwezinto ezivela ngaphandle kunezinto ezibangela izifo njengamavirus, amaparasite, amafungus, namabacterium.

Isikhumba—Singaphezu Nje Kokuba Isembozo Esingasho Lutho

Isikhumba indlela yokuqala yokuzivikela ngokumelene nalabahlaseli abavela ngaphandle. Njengoba singaphezu nje kokuba isembozo esivikelayo esingasho lutho, sinamangqamuzana axwayisa isimiso sokuzivikela komzimba ngamagciwane ahlaselayo. Izigidi eziyizinkulungwane zamabacterium anobungane zihlala esikhunjeni—kwezinye izindawo ezicishe zibe yizigidi ezintathu isentimitha skwele ngalinye. Amanye aveza amafatty acid aphazamisa ukukhula kwezinhlobo eziyingozi zamabacterium nefungi. IScientific American, kaJune 1985, ibiza isikhumba ngokuthi “isici esibalulekile sesimiso sokuzivikela komzimba,” esinamangqamuzana akhethekile “anezindima ezibambisanayo ekusabeleni kubahlaseli bangaphandle.”

Okusiza isikhumba njengengxenye yesembozo somzimba esivikelayo ulwelwesi olumboza ingaphakathi lomzimba. Lolulwelwesi lukhiqiza amafinyila abamba amagciwane. Amathe, amafinyila asemankankeni, nezinyembezi kunezinto ezibulala amagciwane. Icilium esazinwele esemigudwini yomoya eholela emaphashini isunduzela amafinyila kanye nodoti emphinjeni, lapho kungakhishwa khona ngokuthimula nangokukhwehlela. Uma noma ibaphi abahlaseli befinyelela esiswini, babulawa ama-acid lapho, bancibilikiswe amaenzyme agayayo, noma babambeke emafinyeleni amboze isisu kanye namathumbu. Ekugcineni, bakhishwa nokunye ukungcola komzimba.

Ama“phagocyte” Nama“lymphocyte”—Izibhamu Ezinkulu!

Kodwa lokhu kumane nje kuyizimpi ezincane uma kuqhathaniswa nezimpi ezinkulu ezibambana ngezihluthu lapho izidalwa ezingaziwa zeqa izivikelo ezingaphandle futhi zingene egazini nasezicutshini zomzimba noma uketshezi. Zisuke sezihlasele indawo enezibhamu ezinkulu yesimiso sokuzivikela komzimba—amangqamuzana amhlophe egazi, anamandla ayizigidi eziyizigidi ezimbili. Azalelwa emnkantsheni wethambo—cishe isigidi njalo ngomzuzwana—ayakhula aqine futhi akhe izigaba ezintathu ezingefani: amaphagocyte kanye nezinhlobo ezimbili zamalymphocyte, okuthiwa, ama-T cell (izinhlobo ezintathu ezinkulu—amangqamuzana awumsizi, awumcindezeli, nawumbulali) kanye nama-B cell.

Manje, isimiso sokuzivikela komzimba kungenzeka sinebutho eliqinile eliyizigidi eziyisigidi, kodwa isosha ngalinye likwazi ukulwa nohlobo olulodwa kuphela lomhlaseli. Phakathi nesifo kungavezwa izigidi zamagciwane, futhi wonke lawomagciwane ayoba nohlobo olufanayo lweantigen. Kodwa izifo ezingefani, ngisho nezinhlobonhlobo zesifo esifanayo, zinama-antigen angefani. Ngaphambi kokuba ama-T cell nama-B cell ahlasele labahlaseli, kufanele abe nezinzwa ezinganamathela kuma-antigen awo akhethekile. Nokho, kuma-T cell nakuma-B cell, kufanele kube nezinzwa eziningi ezingafani, izinzwa ezikhethekile zama-antigen azo zonke izifo ezihlukahlukene—kodwa i-T cell noma i-B cell ngayinye inenzwa ekhethekile yeantigen eyodwa kuphela yesifo.

UDaniel E. Koshland, Jr., umhleli kamagazini iScience, uthi ngaleliphuzu: “Isimiso sokuzivikela komzimba siklanyelwe ukubona abahlaseli abavela kwenye indawo. Ukuze senze kanjalo sishukumisa izinhlobo ezihlukahlukene ezingu-10¹¹ (100-000 000 000) zezinzwa zokuzivikela komzimba ukuze kuthi noma umhlaseli ovela ngaphandle ekusiphi isimo noma akheke kanjani kube khona inzwa ehambelana naye ezombona futhi ibangele ukuba akhishwe.” (Science, June 15, 1990, ikhasi 1273) Kanjalo, kunamaqembu ama-T cell nama-B cell okuthi phakathi kwawo, akwazi ukuzifanelanisa nanoma iyiphi iantigen yesifo engena emzimbeni wethu—njengoba nje ukhiye ungena khaxa engidini.

Nanku umfanekiso. Abenzi bezikhiye ababili basebenza ngokwehlukana ngokuphelele. Omunye wabo wenza izigidi zezingidi zazo zonke izinhlobo kodwa ezingenabo okhiye. Omunye wenza izigidi zokhiye bazo zonke izinhlobo kodwa ezingenazo izingidi. Khona-ke izigidi eziyizinkulungwane zezingidi kanye nokhiye kufakwa esitsheni esikhulu futhi kunyakazisiswe kahle, futhi ukhiye ngamunye uthola ingidi futhi uzingenele ngokwawo kuyo. Ingabe akunakwenzeka? Ingabe kuyisimangaliso? Kungabonakala kunjalo.

Njengezingidi ezinezimbobo zokhiye, izigidi zamagciwane kanye nama-antigen awo zihlasela umzimba wakho futhi zijikeleze egazini nasoketshezini lomzimba. Njengokhiye abayizigidi, amangqamuzana akho esimiso sokuzivikela komzimba kanye nezinzwa zawo nawo ajikeleza lapho futhi angene kuma-antigen amagciwane ahambelana nawo. Ingabe akunakwenzeka? Ingabe kuyisimangaliso? Kungase kubonakale kunjalo. Kodwa isimiso sokuzivikela komzimba siyakwenza.

Uhlu ngalunye lwamalymphocyte lunendima yalo ekhethekile oluyifezayo ekulweni nesifo. Ama-T cell awumsizi (olunye uhlobo lwama-T cell amakhulu) abalulekile. Yiwona akha amabutho ahlukahlukene esimiso sokuzivikela komzimba, aqondise amacebo empi. Eshukunyiswa ukuba khona kwama-antigen ayisitha, ama-T cell awumsizi esebenzisa izimpawu zamakhemikhali (amaprotein okuthiwa amalymphokine) avivisa amabutho esimiso sokuzivikela komzimba futhi andise amabutho awo ngezigidi. Ngokuzenzakalelayo, ama-T cell awumsizi yiwona akhethwa igciwane lengculaza ukuze liwahlasele. Lapho esenqotshiwe, isimiso sokuzivikela komzimba siyahluleka ukusebenza, okushiya isisulu sengculaza sivulekele zonke izinhlobo zezifo.

Nokho, ngalesikhathi, cabangela indima ye-T cell ewumsizi kanye namaphagocyte, okungamangqamuzana adla amangqamuzana afile. Igama lawo lisho “ukudla amangqamuzana.” Awakhethi—adla noma yini ebonakala isoleka, kungakhathaliseki ukuthi amagciwane avela ngaphandle, amangqamuzana afile, noma omunye udoti. Asebenza kokubili njengebutho elivimbela amagciwane esifo nanjengomkhucululi oshwabadela imfucumfucu. Aze adle ngisho nezinto ezingcolisayo ezivela entuthwini kagwayi ezenza amaphaphu abe mnyama. Uma ukubhema kuqhubeka isikhathi eside, intuthu yonakalisa amaphagocyte ngesivinini esishesha ngaphezu kwakhiqizwa ngaso. Nokho, okunye kokudla kwalamangqamuzana adlayo, akugayeki, kuyabulala nokubulala—ngokwesibonelo, uthuli lwesilica nezinto zeasibhestasi.

Amaphagocyte ayizinhlobo ezimbili, amaneutrophil namamacrophage. Umnkantsha wethambo ukhipha amaneutrophil athi mawabe yizigidi eziyizinkulungwane eziyikhulu ngosuku. Aphila izinsuku ezimbalwa nje kuphela, kodwa phakathi nokuhlaselwa igciwane lesifo, inani lawo landa kakhulu, liphindeke kahlanu. Ineutrophil ngayinye ingabamba futhi ibulale amabacterium afinyelela ku-25 bese iyafa, kodwa amanye ayaqhubeka evela. Ngakolunye uhlangothi, amamacrophage angabulala abahlaseli abayikhulu ngaphambi kokuba afe. Makhudlwana, anamandla kakhudlwana, futhi aphila isikhathi esithe xaxa kunamaneutrophil. Asabela nje ngendlela eyodwa kuphela kokubili kubahlaseli nasemfucumfucwini—ayakudla. Nokho, bekungaba yiphutha ukucabanga ngamamacrophage njengezinto eziqoqa udoti kuphela. “Akhiqiza izinhlobo ezihlukahlukene, ezifinyelela ku-50 zamaenzyme kanye nezinto ezivimbela ukukhula kwamagciwane” futhi asebenze njengamaketanga awumxhumanisi “hhayi nje phakathi kwamangqamuzana esimiso sokuzivikela komzimba kuphela kodwa futhi namangqamuzana akhiqiza amahormone, amangqamuzana emizwa, ngisho namangqamuzana obuchopho.”

Sizani! Isitha Siphakathi Kwethu!

Lapho imacrophage igwinya igciwane eliyisitha, yenza okungaphezu nje kokulidla. Cishe njengawo wonke amangqamuzana omzimba, endaweni yayo engaphandle inamamolecule eMHC ewaveza njengengxenye yayo. Kodwa lapho imacrophage idla igciwane, imolecule MHC idonsa futhi iveze obala ingxenyana yeantigen yalesitha kwesinye sezidladla ezingaphandle kwayo. Khona-ke, lolucezwana lweantigen lusebenza njengefulege elibomvu esimisweni sokuzivikela komzimba, luhlaba umkhosi wokuthi kunento evela ngaphandle egcaluzayo phakathi kithi.

Ngokuhlaba lomkhosi, imacrophage ibiza amabutho empi, amamacrophage engeziwe, ayizigidi! Futhi lapha yilapho i-T cell ewumsizi ingenela khona. Izinkulungwane zezigidi zawo ziyahambahamba emzimbeni, kodwa imacrophage kufanele ifune uhlobo oluthile olukhethekile. Idinga olunohlobo lwenzwa ezongena kuyiantigen ethile evezwa imacrophage.

Lapho loluhlobo lwe-T cell ewumsizi lufika futhi luxhumana neantigen yesitha, imacrophage ne-T cell ewumsizi kwenza izimpawu zamakhemikhali. Lamakhemikhali afana namahormone, noma amalymphokine, angamaprotein angavamile eza nezinhlobonhlobo ezididayo zemisebenzi ukuze aqondise futhi asekele ukusabela kwesimiso sokuzivikela komzimba emagciwaneni ezifo. Umphumela uwukuthi kokubili imacrophage ne-T cell ewumsizi aqala ukuzandisa kakhulu. Lokhu kusho ukuba khona kwamamacrophage amaningi ukuba adle amagciwane engeziwe ahlaselayo kanye nokuba khona kohlobo oluqonde ngokwengeziwe lwama-T cell awumsizi ahlasela ama-antigen avezwa amamacrophage. Khona-ke inani lamabutho okuvikela umzimba landa kakhulu, futhi lonke uquqaba lwalamagciwane esifo luyaqothulwa.

[Imibhalo yaphansi]

[Ibhokisi ekhasini 4, 5]

“Izikhali Zokuzenzela Zokulwa Nanoma Yimuphi Umhlaseli Ocatshangelwayo”

Isimiso sokuzivikela komzimba silondoloza “izikhali esizakhele zona zokulwa nanoma yimuphi umhlaseli ocatshangelwayo.” Lezikhali eziyinqwaba “zaziwa ngokuthi zikhiqizwa isimiso esiyinkimbinkimbi samangqamuzana ofuzo lapho izingxenye zamangqamuzana ofuzo zihlelwa kabusha futhi ziphinde zihlanganiswe.” Manje umbiko walokho okukhulu okutholwe muva nje unikeza ukukhanya ngokuthi lokhu kwenzeka kanjani.

“Ingqamuzana yofuzo esanda kutholwa kukholelwa ukuthi ifeza indima ebalulekile kuleyonqubo yokuhlanganisa kabusha amangqamuzana ofuzo. Izazi zesayensi ziye zetha lengqamuzana ngokuthi iRAG-1 okusho ukuthi (recombination activating gene [ingqamuzana ebangela ukuhlanganiswa kabusha]).” Lokho okwatholwa kwabikwa kumagazini iCell, wangoDecember 22, 1989. Kodwa izazi zesayensi eNhlanganweni Ecwaninga Ngesayensi Yezokwelapha YaseWhitehead eCambridge, Massachusetts, U.S.A., ezathola iRAG-1, zikhathazekile ngokuthi “lengqamuzana ehlanganisa kabusha yayingacaci kahle futhi ingasheshi ekuchazeni indlela umzimba oveza ngayo lezinhlobonhlobo zamaprotein okuvikela umzimba angapheli nahlaba umxhwele. Ukuze ubhekane nanoma yiluphi uhlobo lokuhlasela okungenzeka, umzimba kufanele uhlale unezigidi zamasosha omzimba kanye nezinzwa ze-T cell, wonke eme ngendlela engafani ukuze okungenani ambalwa akwazi ukubona lonke uhlobo olusha lwepathogen.”—The New York Times, kaJune 26, 1990.

Ngakho zona lezizazi zesayensi zaqala ukufuna enye ingqamuzana yofuzo ukuze zinqobe lenkinga. Ezinyangeni eziyisithupha kamuva umagazini iScience wangoJune 22, 1990, wabika ukuthi zase zilitholile. “Izazi zesayensi zithi ingqamuzana entsha, iRAG-2, isebenza nengqamuzana yofuzo yokuqala ekuhlanganiseni ngokushesha ngokwengeziwe amasosha omzimba kanye nezinzwa ezingamaprotein. Lapho esebenza ewumshungu, amangqamuzana ofuzo amabili angahlanganisa kabusha izingxenye zesimiso sokuzivikela komzimba kangcono ngokuphindwe izikhathi ezisukela kwezingu-1 000 kuya esigidini ngaphezu kwanoma iliphi ingqamuzana yofuzo ezimele.” Esebenza njengomshungu, iRAG-1 neRAG-2 athulula izigidi zamasosha omzimba kanye nezinzwa zama-T cell ezidingekayo.

Lokhu kucwaninga kuchazwa “njengobuciko obukhulu besayensi.” Kuyimpumelelo enkulu yokuthola okuthile engase ivule umnyango wokuqonda kangcono ezinye izifo zamangqamuzana ofuzo izimiso zokuzivikela komzimba ezihlulekayo kuzo.—The New York Times, kaDecember 22, 1989.