es irable ▁re actions ▁produced ▁by ▁the ▁normal ▁imm une ▁system , ▁including ▁all erg ies ▁and ▁auto imm unity . ▁They ▁are ▁usually ▁referred ▁to ▁as ▁an ▁over - re action ▁of ▁the ▁imm une ▁system ▁and ▁these ▁re actions ▁may ▁be ▁dam aging , ▁un com fort able , ▁or ▁occasionally ▁fatal . ▁ ▁Hyp ers ens itivity ▁re actions ▁require ▁a ▁pre - sens it ized ▁( imm une ) ▁state ▁of ▁the ▁host . ▁The ▁G ell ▁and ▁Co omb s ▁classification ▁of ▁hyp ers ens itivity ▁is ▁the ▁most ▁widely ▁used , ▁and ▁distingu ishes ▁four ▁types ▁of ▁imm une ▁response ▁which ▁result ▁in ▁by stand er ▁t issue ▁damage . ▁ ▁Co omb s ▁and ▁G ell ▁ ▁classification ▁ ▁Type ▁V ▁▁ ▁This ▁is ▁an ▁additional ▁type ▁that ▁is ▁sometimes ▁( es pecially ▁in ▁the ▁UK ) ▁used ▁as ▁a ▁distinction ▁from ▁Type ▁ 2 . ▁ ▁Instead ▁of ▁binding ▁to ▁cell ▁surfaces , ▁the ▁ant ib od ies ▁recogn ise ▁and ▁bind ▁to ▁the ▁cell ▁surface ▁re cept ors , ▁which ▁either ▁prevents ▁the ▁intended ▁lig and ▁binding ▁with ▁the ▁re ceptor ▁or ▁m im ics ▁the ▁effects ▁of ▁the ▁lig and , ▁thus ▁imp air ing ▁cell ▁signal ing . ▁ ▁Some ▁clin ical ▁examples ▁are : ▁Gra ves ' ▁disease ▁My as then ia ▁gra vis ▁ ▁The ▁use ▁of ▁Type ▁ 5 ▁is ▁rare . ▁These ▁conditions ▁are ▁more ▁frequently ▁class ified ▁as ▁Type ▁ 2 , ▁though ▁sometimes ▁they ▁are ▁specifically