Phosphorylated Signal transducer and activator of transcription 3 (STAT3) and Signal transducer and activator of transcription 5A/5B (STAT5A and STAT5B, respectively, or STAT5) dissociate from the Interleukin-15 (IL15) receptor complex, which consists of IL15, Interleukin-15 receptor subunit alpha (IL15RA, IL15Rα), Interleukin-2 receptor beta subunit (IL2RB, IL2Rβ), Tyrosine-protein kinase JAK1 (JAK1), Cytokine receptor common subunit gamma (IL2RG, IL2Rγ) and Tyrosine-protein kinase JAK3 (JAK3). Recombinant IL15 (10 ng/mL) induces the translocation of pSTAT3 to the nucleus (Giron Michel et al. 2003). In mast cells, IL15-stimulated STAT5 activation has been suggested to involve Tyrosine protein kinase JAK2 (JAK2) rather than JAK1/JAK3 signaling (Waldman & Tagaya 1999). More in detail, mast cells have unique receptors for IL15 i.e., IL15 Receptor X (IL15RX). Binding of IL15 with IL15 RX (Tagaya et al. 1996) on mast cells induces mast cell growth by activation of JAK2/STAT5 pathways and mast cell differentiation by Non-receptor tyrosine-protein kinase TYK2/Signal transducer and activator of transcription 6/Interleukin-4 pathway(TYK2/STAT6/IL4 pathway) (Jackson et al. 2005). This is black box event because dissociation is inferred from the identification of STAT3 and STAT5 in DNA binding complexes after IL15 stimulation (Johnston et al. 1995, Giron Michel et al. 2003).