<prompt> Memory cell in immune system are long lived and escape apoptosis because of:Insulin like growth factorFibroblast growth factor FGFPlatelet derived growth factorNerve growth factor  <response>: D i.e. Nerve growth factorNerve growth factor inhibits apoptosis in memory B cellsQ inactivation of p38 MAPK, prevention of antiapoptotic factor Bcl-2 phosphorylation i.e. maintaining its integrity cytochrome c releaseAlthough other growth factors like FGF, PDGF and IGF can also prolong the survival, it is the nerve growth factor that is most impoant in immoalization of memory cells.Growth factor -- activate P13 kinase -- activate Akt -- inactivates procaspase 9 inhibit Fast synthesis 