▁ 3 . ▁ ▁Cross - prim ing ▁ ▁Cross - prim ing ▁refers ▁to ▁the ▁stim ulation ▁of ▁ant igen - specific ▁CD 8 + ▁c yt ot ox ic ▁T ▁l ym ph ocy tes ▁( CT L s ) ▁by ▁d end rit ic ▁cell ▁present ing ▁an ▁ant igen ▁acquired ▁from ▁the ▁outside ▁of ▁the ▁cell . ▁Cross - prim ing ▁is ▁also ▁called ▁imm un ogen ic ▁cross - presentation . ▁This ▁mechanism ▁is ▁vital ▁for ▁prim ing ▁of ▁C TL s ▁against ▁vir uses ▁and ▁tum ours . ▁ ▁Im m une ▁prim ing ▁( in verte br ate ▁imm unity ) ▁▁ ▁Im m une ▁prim ing ▁is ▁memory - like ▁phenomen on ▁described ▁in ▁in verte br ate ▁tax a ▁of ▁animals . ▁It ▁is ▁evolution ary ▁advantage ous ▁for ▁an ▁organ ism ▁to ▁develop ▁a ▁better ▁and ▁faster ▁secondary ▁imm une ▁response ▁to ▁path ogen , ▁which ▁is ▁harm ful ▁and ▁which ▁it ▁is ▁likely ▁to ▁be ▁exposed ▁again . ▁In ▁verte br ates ▁imm une ▁memory ▁is ▁based ▁on ▁adapt ive ▁imm une ▁cells ▁called ▁B ▁and ▁T ▁l ym ph ocy tes , ▁which ▁provide ▁an ▁en hanced ▁and ▁faster ▁imm une ▁response , ▁when ▁challeng ed ▁with ▁the ▁same ▁path ogen ▁for ▁a ▁second ▁time . ▁It ▁was ▁assumed ▁that ▁in verte br ates ▁do ▁not ▁have ▁memory - like ▁imm une ▁functions , ▁because ▁of ▁their ▁lack ▁of ▁adapt ive ▁imm unity . ▁But ▁in ▁recent ▁years ▁evidence ▁supporting ▁inn