Interleukin-23 is secreted to the extracellular region.
T helper 1 cell (Th1) cytokines such as Interferon-gamma (IFNG) and Interleukin-12 (IL12) are transported through the tubulovesicular system to small secretory vesicles from their sites of storage in crystalloid granules (Spencer et al. 2009, Melo et al. 2005). In neutrophils the precise intracellular location of cytokines and chemokines is unknown, although histological examination of mature peripheral neutrophils suggests that Interleukin-6, IL12 and C-X-C motif chemokine 2 (CXCL2) may be stored within secretory vesicles or tertiary granules (Denkers et al. 2003, Stanley & Lacy 2010).
This reaction is a black box event because we know this Interleukin-23 heterodimeric protein is secreted but do not know the storage compartment and mechanism involved in the traslocation.