▁a ▁critical ▁role ▁in ▁He pat itis ▁C ▁attachment ▁and / or ▁cell ▁entry ▁by ▁interact ing ▁with ▁virus ' ▁E 1 / E 2 ▁g ly cop rote ins ▁heter od imer . ▁The ▁large ▁ext rac ell ular ▁loop ▁of ▁CD 8 1 ▁bind s ▁the ▁he pat itis ▁E 2 ▁g ly cop rote in ▁dim er . ▁ ▁H CV - E 2 ▁and ▁CD 8 1 ▁binding ▁K d ▁is ▁ 1 . 8 ▁n M . ▁ ▁H CV - E 2 ▁engaged ▁CD 8 1 ▁is ▁only ▁ 3 0 % ▁internal ized ▁after ▁ 1 2 hr , ▁suggesting ▁CD 8 1 ▁may ▁be ▁primarily ▁an ▁attachment ▁re ceptor ▁for ▁H CV . ▁ ▁It ▁also ▁appears ▁to ▁play ▁a ▁role ▁in ▁li ver ▁invasion ▁by ▁Pl as mod ium ▁species . ▁CD 8 1 ▁is ▁required ▁for ▁Pl as mod ium ▁viv ax ▁sp or oz o ite ▁entry ▁into ▁human ▁he pat ocy tes ▁and ▁for ▁Pl as mod ium ▁yo el ii ▁sp or oz o ite ▁entry ▁into ▁mur ine ▁he pat ocy tes . ▁ ▁H IV ▁g ag ▁prote ins ▁use ▁t et ras pan in ▁en rich ed ▁micro dom ains ▁( cont aining ▁minim ally ▁CD 8 1 , ▁CD 8 2 , ▁CD 6 3 ) ▁as ▁a ▁platform ▁for ▁vir ion ▁assembly ▁and ▁release . ▁ ▁Pur ified ▁H IV ▁produced ▁by ▁M OL T \ H IV ▁cells ▁contains ▁CD 8 1 . ▁