ith el ium ▁of ▁the ▁resp ir atory ▁tract ▁which ▁kill ▁many ▁stra ins ▁of ▁b acter ia . ▁ ▁Those ▁b acter ia ▁that ▁are ▁resist ant ▁to ▁ant im icro b ial ▁pe pt ides ▁are ▁killed ▁by ▁a ▁variety ▁of ▁re active ▁o xygen ▁species ▁produced ▁by ▁ph ag ocy tes . ▁In ▁a ▁third ▁line ▁of ▁defense ▁and ▁as ▁a ▁last ▁resort , ▁persistent ▁b acter ial ▁in fe ctions ▁which ▁escape ▁the ▁inn ate ▁imm une ▁system ▁are ▁elimin ated ▁by ▁the ▁adapt ive ▁imm une ▁system . ▁ ▁L act o fer rin ▁▁ ▁L act o fer rin ▁( L F ) ▁is ▁a ▁mult if unction al ▁protein ▁which ▁is ▁an ▁essential ▁part ▁of ▁the ▁resp ir atory ▁tract ▁ant im icro b ial ▁defense ▁system . ▁L F ▁prote ol ysis ▁produces ▁the ▁small ▁pe pt ides ▁la ct o fer ric in ▁and ▁k ali oc in - 1 ▁both ▁with ▁ant im icro b ial ▁activity . ▁ ▁Re active ▁o xygen ▁species , ▁o xygen ated ▁comp ounds ▁▁ ▁Ph ag ocy tes ▁possess ▁a ▁super ox ide - produ cing ▁N AD PH ▁ox id ase ▁en zym e ▁complex . ▁Other ▁cells ▁in ▁the ▁resp ir atory ▁tract ▁also ▁produce ▁super ox ide ▁and ▁hydro gen ▁per ox ide ▁through ▁the ▁activity ▁of ▁dual ▁ox id ase ▁ 2 ▁prote ins , ▁also ▁known ▁as ▁Du ox 2 . ▁ ▁The ▁super ox ide ▁generated ▁by ▁these ▁en zym