▁of ▁pit rak in ra ▁impro ves ▁the ▁control ▁over ▁ast h ma ▁sympt oms . ▁ ▁In ▁addition ▁to ▁improvements ▁in ▁the ▁late ▁ast hm atic ▁response , ▁measurement ▁of ▁Fra ction al ▁Exp ir atory ▁N it ric ▁Ox ide ▁( F EN O ) ▁indicates ▁that ▁the ▁rest ing ▁infl am mat ory ▁status ▁of ▁the ▁l ungs ▁is ▁significantly ▁at ten u ated ▁after ▁in hal ation ▁of ▁pit rak in ra ▁for ▁ 4 ▁weeks . ▁This ▁result ▁supports ▁observations ▁that ▁IL - 4 ▁and ▁other ▁pro - infl am mat ory ▁medi ators ▁indu ce ▁nit ric ▁ox ide ▁synth ase ▁( i N OS ) ▁through ▁ST AT 1 ▁and ▁ST AT 6 ▁in ▁ep ith el ial ▁cells . ▁Bas al ▁F EN O ▁could ▁be ▁more ▁dependent ▁on ▁up - reg ulation ▁of ▁i N OS ▁by ▁IL - 4 ▁and ▁IL - 1 3 , ▁whereas ▁the ▁increase ▁in ▁F EN O ▁after ▁aller gen ▁challenge ▁could ▁involve ▁additional ▁path ways ▁in ▁ep ith el ial ▁cells ▁and ▁perhaps ▁macro ph ages ▁that ▁are ▁not ▁affected ▁by ▁the ▁in hib ition ▁of ▁IL - 4 R α . ▁Pit rak in ra ▁may ▁down - reg ulate ▁bas eline ▁Th 2 ▁infl amm ation ▁in ▁the ▁ast hm atic ▁lung ▁while ▁not ▁inter fer ing ▁with ▁the ▁lung ’ s ▁natural ▁def enses ▁in ▁contact ▁with ▁large ▁amounts ▁of ▁foreign ▁aller gen . ▁ ▁Ad verse ▁events ▁Pit rak in ra ▁is ▁associated