PRF1 and Behcet disease: Interestingly, a CD8brightCD56+ T cells population with cytolytic potential have been demonstrated in patients with active Behçet uveitis; these cells are able to exert their harmful effects through both Fas ligand-dependent and perforin-dependent pathways.[29] Thus, also at the early stages of intestinal involvement, both CD4+ and CD8+ T cells are able to express their potential cytolytic damage in BD patients, via both perforin- and Fas–Fas ligand-mediated pathways.