CD69 and neoplasm: Co-stimulatory CD69 is a type II glycoprotein with important functions in regulating inflammation through T cell migration, retention in tissues, and plays an important role sustaining T cell activation, proliferation, cytolytic activity (Borrego et al 1999) but also in inducing the exhaustion of tumour-infiltrating T cells perhaps as a result of prolonged T cell activation promoted by CD69 signalling in the T cells (Mita et al. 2018).