Son of sevenless homolog 2 (SOS2) is believed to bind the Interleukin-15 (IL15) receptor complex (Mishra et al. 2014). This is inferred from the binding of GRB2 to Interleukin-2 receptor beta subunit (IL2RB, IL2Rβ) in the IL15 receptor complex (Zambricki et al. 2005) and Interleukin-2 receptor complex (Zhu et al. 1994) and from events that follow SHC-GRB2 association in IL2 receptor signaling. The Interleukin-15 (IL15) receptor complex consists mainly of IL15, Interleukin-15 receptor alpha subunit (IL15RA, IL15Rα), Interleukin-2 receptor beta subunit (IL2RB, IL2Rβ), which is associated with JAK1 and Interleukin receptor gamma subunit, which is associated with JAK3 (Johnston et al. 1995). In IL2 signaling, the resulting GRB2:SOS complex activates the Ras-Raf pathway (Zhu et al. 1994) and is believed to participate in similar events in IL15 signaling (Anduyah et al. 1997, Mishra et al. 2014). This is a black box event because SOS1 binding to GRB2 in response to IL15 has not been demonstrated.