Besides the central nervous system, it is expressed at high levels in peripheral blood leukocytes, and thus the BARK/beta-arrestin system is believed to play a major role in regulating receptor-mediated immune functions.
Pored centralnog nervnog sistema, on je izražen u visokim nivoima u perifernim krvnim leukocitima, i stoga se za BARK/beta-arestinski sistem da ima značajnu ulogu u regulaciji receptorom-posredovanih imunskih funkcija.