This is the peer reviewed version of the following article: Hasan, Md. S., Ryan, P. L., Bergmeier, L. A. and Fortune, F. (2017), Circulating NK cells and their subsets in Behçet's Disease. Clin Exp Immunol. doi:10.1111/cei.12939, which has been published in final form at http://dx.doi.org/10.1111/cei.12939. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.