- Th^nh phan hoa hgc va tmh khong thuan nhat: Chi kich thuoc vd tinh la chua du dl xac dinh
1.2.4.ciu tr^c khdng huyit thanh
Cau triic dien hinh
Khang nguyen
Vi tri kit hop Viirg txAn dii
^ Vi tri kit hop Viirg btin C6i
Chufiinhfl ^ /
Chuit n$ng-
Ciu Uen k^l
disulfidfl
Khdng th4
Hinh 1.1. Cau tnic cua m$t phan tu* khdng huylt thanh
Phdn tii khdng huyit thanh ciu t^o td 4 chuoi polypeptide, gdm hai chudi nang (H, heavy, tiing Anh, mdu tim trong hinh 3) gilng hdt nhau va hai chuoi nhe (L, light, tieng Anh, mdu xanh la trong hinh 3) cilng gidng het nhaụ Cd hai loai chuoi nh? K (kappa) va X (lambda), do do hai chudi nh? cua moi phdn tii immunoglobulin chi cd the cimg Id K hodc cimg Id X. Cdc chudi cua
immunoglobulin lien kit vdi nhau bdi cdc cdu ndi disulfide va co dp dan hdi nhat dinh (hinh 2 vd 3). Mgt phin ciu tnic cua cac chudi thi cd dinh nhung phdn dau cua hai "cdnh tay" chG Y thi rat biln thien giiia cdc khdng huylt thanh khde nhau, de t^o nen cdc vi tri ket hgp cd khd ndng phdn ling d^c hỉu vdi cdc khdng nguyen tuong iing, dieu nay tuong tu nhu mpt enzyme tiep xiic vdi co chit ciia nd. Cd thi tam so sdnh s\r dac hieu cua phdn iing khang huylt thanh-khang nguyen vdi d khda vd chia khdạ
Hinfa 1.2. Scr do cac chuoi cua mot khang huylt thanh
Cdc domain hang dinh (C, constant, tieng Anh) dac trung bdi cac chudi amino acide khd
gidng nhau giiia cac khdng huylt thanh. Domam hdng dinh ciia chudi nhe ky hieu la CL- Cdc chudi ndng chira 3 h o ^ 4 domain hdng dinh, tiiy theo ldp khdng huylt thanh CHI, CH2, CH3 vd CH4. Cdc domain hdng djnh khdng cd vai trd nhdn dien khdng nguyen, chiing lam nhiem vu cau ndi vdi cdc te bdo mien djch ciing nhu cac bd thẹ Do do, phdn "chan" cua chii Y cdn dugc ggi la Fc (tiic la
phdn hôt đng sinh hgc ciia khang huylt thanh F: fragment, c: cristallisable)
Cdc domain bien thien
Mdi immunoglobulin cd 4 domain bien thien (V, variable, tieng Anh) d diu tan hai "cdnh
tay" cua chii Ỵ S\r ket hgp giiia 1 domain bien thien tren chudi ndng (VH) vd I domain bien thien tren chudi nhe (VL) tao nen vi tri nhan dien khdng nguydn (cdn ggi Id paratope). Nhu vay, moi immunoglobulin cd hai vi tri gdn khang nguyen. Hai vj tri nay gidng nhau nhu due, qua đ mgt khang huyet thanh cd the gdn dugc vdi 2 khdng nguyen gidng nhaụ Hai "cdnh tay" cua chií Y cdn
ggi la Fab (tuc Id phan nhdn biet khdng nguyen, ¥: fragment, ab: antigen binding). Domain khdng
nguyen nai gdn vdo khdng huylt thanh ggi la epitopẹ
Cdc domain sd di ggi Id bien thien vi chiing khac nhau rat nhieu giiía cdc khdng huyet thanh. Chinh sy biln thien da dang nay giiip cho he didng cdc khdng huyet thanh nhan biet dugc nhilu loai tdc nhdn gay bgnh khde nhaụ Ca che tao nen su bien thien nay se dugc de cap d nhiing phdn saụ
M?o nhd (khdng chinh thiic): allo=tir chii allele —»• allotype: khdng nguyen cua cdc cd the cimg lodi mang allele khde nhaụ
1.2.5. Ai Ifrc ciia khdng huyit thanh vdi khdng nguyen
Lidn kit giCra Ididng huylt thanh vd khdng nguyen, tirong tu nhu giiia enzyme va co chat, cd inh t h u ^ nghich. Lien ket m^nh hay yeu tiiy vao sd lugng Hen ket vd do dac hieu giiia vung nhdn li^n khdng nguyen tren khdng huyet thanh va cau true epitope tuong iing.
Ai luc ciia khing huylt thanh dii vdi khing nguyen li hop luc cua cic luc hen kit yen khdng dong hda tn (lien kit hydro, luc van der Waals va cac lien kit ion...). Cac luc lien kit yeu nay chi cd tic dung trong mdt bin kinh nhd, do đ su dac hieu (hay tinh chit bo sung) trong ciu tnic khdng gian 3 ehilu ciia 2 vimg phin til cd vai trd quyet dinh doi vdi ii luc ciia khing huyet thanh vdi khing nguyen.
Nhu vay, mpt khang nguyen cd the dupe nhan dien bdi nhieu khing huyet thanh vdi đ die hiSu khic nhau, đng khing huylt thanh nao phii hpp nhit vl ciu tnic 3 chilu vdi epitope se dupe khulch truong m^nh nhit.
1.2.7. Vai trd cua khang huyet thanh
Trong mpt dip img miln dich, khing huylt thanh cd 3 chile ning chinh: gin vdi khing nguyen, kich hoat hp thong bo the vi huy đng cic tl bao mien dich.
Li€n kit vdi khing nguySn
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Hinh 1.3. Cic a$c to cua vi khuan ben canh mgt te bao ccr the
Cic immunoglobulin cd khi nang nhin dien va gin mpt cich die hipu vdi 1 khing nguyen tuong img nhd cic domain biln thien. Mpt thi du dl mieu ti Ipi ich cua khang huylt thanh la trong phin img chong dpc to vi khuin. Khing huylt thanh gin vdi vi qua do trung hda dpc to, ngin ngira sir bim dinh ciia cic dpc to tren len cic thu thi tl biọ Nhu vay, cic tl bio co the trinh dupe cic roi l o ^ do cic dpc to đ giy rạ
Tuong tu nhu viy, nhilu vims vi vi khuan chi gay benh khi bim dupe vio cic tl bio co thị Vi khuin sii dyng cic phan til bim dinh li adhesine, cdn virus sd hiru cac protein cd dinh tren ldp vd ngoaị Cic khang huyet thanh khing-adhesine va khing-proteine capside virus se ngin chin cic vi sinh vat niy gin vio cac te bao dich ciia chimg,
Khang the , . • .
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Hinh 1.4. Cac doc to tren bj trung hoa boi khang huyet thanh
Mgl trong nhQ-ny ca che bao \ e ca the ciia khang hmct thanh la \ lec hoat hoa dong thac bd thi B 6 thi: !a tap hop cac protein huyet tircrng khi duoc hoat hoa se tieu diet cac vi khuan xdm hai bdng each {1) due cac Id thung tren vi khuan. (2i tao dieu kien cho hien tuong thuc bao, (3) thanh igc cdc phirc hop inien djch va (4) phong thich cac phan tir hoa hu^dng dong.
Hoat hoa cac te bao mien dich
Sail khi gan vao khang nguyen a dau bien thien iFab). khang hu\et thanh co the lien ket vdi
cdc te bdo mien dich a dau hang dinh (Fc). Nhung tuong lac nay co tam quan trong dac biet trong đp ling mien dich, Nhu vay, cac khang huyet ihanh gan vdi mdt vi khuan co the lien ket vdi mdt
d^i thyc buo va khdi dong hien tuong thuc bao, Cac te bao lympho NK {Nuiurul KiHer) cd the thuc
hi§n chiic nang dpc te bao va ly giai cac vi khuan bi opsonme hda bdi cac khang huyet thanh.