▁the ▁ant igen ▁of ▁a ▁foreign ▁blood ▁cell ▁and ▁recognize ▁it ▁as ▁a ▁path ogen ▁because ▁the ▁ant igen ▁is ▁un famil iar . ▁It ▁is ▁not ▁easy ▁to ▁class ify ▁red ▁blood ▁cell ▁recognition ▁as ▁intr insic ▁or ▁extr insic , ▁as ▁a ▁foreign ▁cell ▁may ▁be ▁recognized ▁as ▁part ▁of ▁the ▁organ ism ▁if ▁it ▁has ▁the ▁right ▁ant ig ens . ▁ ▁Det r iment al ▁mut ations ▁▁ ▁T LR ▁mut ations ▁ ▁Mut ations ▁in ▁m amm al ian ▁re ceptor ▁prote ins ▁can ▁cause ▁dis orders ▁in ▁cell - cell ▁recognition , ▁increasing ▁individual ▁sus cept ibility ▁to ▁certain ▁path og ens ▁and ▁chron ic ▁conditions . ▁ ▁When ▁mut ations ▁occurs ▁in ▁gen es ▁that ▁code ▁for ▁T LR s , ▁the ▁prote ins ▁can ▁lose ▁the ▁ability ▁to ▁bind ▁with ▁pol ys ac char ides , ▁lip ids , ▁or ▁prote ins ▁on ▁the ▁cell ▁wall ▁or ▁memb rane ▁of ▁single - cel led ▁path og ens , ▁resulting ▁in ▁a ▁failure ▁of ▁the ▁inn ate ▁imm une ▁system ▁to ▁respond ▁to ▁in fection ▁that ▁allows ▁disease ▁to ▁develop ▁rapidly . ▁ ▁In ▁particular , ▁mut ations ▁in ▁the ▁gen es ▁for ▁T LR 2 ▁and ▁T LR 4 ▁have ▁been ▁frequently ▁imp licated ▁in ▁increased ▁sus cept ibility ▁to ▁path og ens . ▁ ▁A ▁thre on ine ▁to ▁c yst e ine ▁mut ation ▁in ▁the ▁T RL 2 ▁gene ▁has ▁been ▁connected ▁to ▁failure ▁to ▁recognize ▁the ▁My c ob acter ium