▁mechanism ▁of ▁action ▁by ▁which ▁th era pe ut ic ▁ant ib od ies ▁or ▁ant ib ody ▁fragments ▁can ▁achieve ▁an ▁ant it um or ▁effect . ▁ ▁Use ▁of ▁CD C ▁ass ays ▁ ▁Th era pe ut ic ▁ant ib od ies ▁ ▁Development ▁of ▁ant it um or ▁th era pe ut ic ▁ant ib od ies ▁involves ▁in ▁vit ro ▁analysis ▁of ▁their ▁effect or ▁functions ▁including ▁ability ▁to ▁trigger ▁CD C ▁to ▁kill ▁target ▁cells . ▁Class ical ▁approach ▁is ▁to ▁inc ub ate ▁ant ib od ies ▁with ▁target ▁cells ▁and ▁source ▁of ▁complement ▁( ser um ). ▁Then ▁cell ▁death ▁is ▁determined ▁with ▁several ▁approaches : ▁▁ ▁Radio active ▁method : ▁target ▁cells ▁are ▁l abeled ▁with ▁ 5 1 Cr ▁before ▁CD C ▁ass ay , ▁chrom ium ▁is ▁released ▁during ▁cell ▁l ysis ▁and ▁amount ▁of ▁radio activity ▁is ▁measured . ▁ ▁Me as uring ▁of ▁the ▁met abol ic ▁activity ▁of ▁live ▁cells ▁( live ▁cells ▁st aining ): ▁after ▁inc ub ation ▁of ▁target ▁cells ▁with ▁ant ib od ies ▁and ▁complement , ▁pl asma ▁memb rane - per me able ▁d ye ▁is ▁added ▁( e . g . ▁cal ce in - AM ▁or ▁res az ur in ). ▁Live ▁cells ▁met abol ise ▁it ▁into ▁imper me able ▁flu ores cent ▁product ▁that ▁can ▁be ▁detected ▁by ▁flow ▁c yt ometry . ▁This ▁product ▁can ’ t ▁be ▁formed ▁in ▁met abol ically ▁in active ▁dead ▁cells .