- gly c ans ▁also ▁bear ▁bis ect ing ▁Gl c NA c ▁and ▁α - 2 , 6 ▁linked ▁s ial ic ▁acid ▁resid ues . ▁ ▁The ▁other ▁part ▁of ▁an ▁ant ib ody , ▁called ▁the ▁Fab ▁region , ▁contains ▁variable ▁sections ▁that ▁define ▁the ▁specific ▁target ▁that ▁the ▁ant ib ody ▁can ▁bind . ▁ ▁By ▁contrast , ▁the ▁F c ▁region ▁of ▁all ▁ant ib od ies ▁in ▁a ▁class ▁are ▁the ▁same ▁for ▁each ▁species ; ▁they ▁are ▁constant ▁rather ▁than ▁variable . ▁ ▁The ▁F c ▁region ▁is , ▁therefore , ▁sometimes ▁incorrectly ▁term ed ▁the ▁" fragment ▁constant ▁region ". ▁ ▁F c ▁bind s ▁to ▁various ▁cell ▁re cept ors ▁and ▁complement ▁prote ins . ▁In ▁this ▁way , ▁it ▁medi ates ▁different ▁phys i ological ▁effects ▁of ▁ant ib od ies ▁( d ete ction ▁of ▁o pson ized ▁particles ; ▁cell ▁l ysis ; ▁de gr an ulation ▁of ▁m ast ▁cells , ▁bas oph ils , ▁and ▁e os in oph ils ; ▁and ▁other ▁processes ). ▁ ▁Engine ered ▁F c ▁fragments ▁In ▁a ▁new ▁development ▁in ▁the ▁field ▁of ▁ant ib ody - based ▁th era pe ut ics , ▁the ▁F c ▁region ▁of ▁imm un og lob ul ins ▁has ▁been ▁engine ered ▁to ▁contain ▁an ▁ant igen - binding ▁site . ▁This ▁type ▁of ▁ant igen - binding ▁fragment ▁is ▁called ▁F c ab . ▁F c ab ▁fragments ▁can ▁be ▁inserted ▁into ▁a ▁full ▁imm