, ▁c - J un , ▁c - My c ▁and ▁N F - κ B . ▁ ▁IL - 1 5 ▁is ▁also ▁able ▁to ▁bind ▁to ▁the ▁ 1 5 R β γ c ▁signal ing ▁complex ▁with ▁intermediate ▁aff inity ▁without ▁requirement ▁for ▁IL - 1 5 R α ▁re ceptor . ▁Upon ▁binding ▁IL - 1 5 ▁to ▁signal ing ▁complex , ▁ ▁kin ases ▁of ▁the ▁S rc ▁family ▁including ▁L ck ▁and ▁F yn ▁are ▁activ ated , ▁and ▁subsequently ▁activ ates ▁P I 3 K ▁and ▁M AP K ▁signal ing ▁path way . ▁The ▁second ▁mechanism ▁of ▁IL - 1 5 ▁action ▁is ▁c is - presentation , ▁when ▁IL - 1 5 ▁is ▁presented ▁by ▁IL - 1 5 R α ▁to ▁ 1 5 R β γ c ▁signal ing ▁complex ▁on ▁the ▁same ▁cell . ▁This ▁mechanism ▁is ▁medi ated ▁by ▁the ▁C - ter minus ▁flex ibility ▁which ▁is ▁medi ated ▁by ▁ 3 2 ▁am ino ▁ac ids ▁linker ▁and / or ▁ 7 4 ▁am ino ▁ac ids ▁long ▁P T ▁region ▁( Fig ure ▁ 6 ). ▁ ▁Function ▁▁ ▁IL - 1 5 ▁regul ates ▁the ▁activation ▁and ▁pro l ifer ation ▁of ▁T ▁and ▁natural ▁k iller ▁( N K ) ▁cells . ▁Sur v ival ▁signals ▁that ▁maintain ▁memory ▁T ▁cells ▁in ▁the ▁absence ▁of ▁ant igen ▁are ▁provided ▁by ▁IL - 1 5 . ▁ ▁This ▁cy tok ine ▁is ▁also ▁imp licated ▁in