- 2 ▁and ▁IL - 1 5 , ▁both ▁of ▁these ▁cy tok ines ▁have ▁similar ▁down stream ▁effects ▁including ▁the ▁induction ▁of ▁B - cell ▁l ym ph oma ▁( B cl - 2 ), ▁M AP ▁( mit ogen - activ ated ▁protein ▁kin ase ) ▁kin ase ▁path way ▁and ▁the ▁ph osph ory lation ▁of ▁L ck ▁( ly m ph ocy te - activ ated ▁protein ▁ty ros ine ▁kin ase ) ▁and ▁Sy k ▁( s ple en ▁ty ros ine ▁kin ase ) ▁kin ases , ▁which ▁leads ▁to ▁cell ▁pro l ifer ation ▁and ▁m atur ation ▁( Fig ure ▁ 5 ). ▁ ▁In ▁m ast ▁cells , ▁the ▁IL - 1 5 R ▁signal ing ▁path way ▁has ▁been ▁found ▁to ▁include ▁Jak 2 ▁and ▁ST AT 5 ▁instead ▁Jak 1 / 3 ▁and ▁ST AT 3 / 5 . ▁Ph osph ory lation ▁ST AT s ▁form ▁trans cription ▁factors ▁and ▁activ ate ▁trans cription ▁of ▁appropriate ▁gen es . ▁The ▁ β ▁chain ▁of ▁IL - 1 5 R ▁rec ruits ▁and ▁also ▁activ ates ▁protein ▁ty ros ine ▁kin ases ▁of ▁the ▁S rc ▁family ▁including ▁L ck , ▁F yn ▁and ▁Lyn ▁kin ase . ▁It ▁also ▁activ ates ▁ph osph at id y lin os it ol ▁ 3 - kin ase ▁( PI 3 K ) ▁and ▁A K T ▁signal ing ▁path way ▁and ▁indu ce ▁expression ▁of ▁trans cription ▁factors ▁including ▁c - F os