Immunostaining of perforin and granzyme B, both cytotoxic effectors, showed only few positive cells without differences between BD and PsA (Table 1), but the SF levels of perforin showed a highly significant four- to fivefold increase in BD (1,168 pg/mL, range 428 to 2,010 pg/mL) versus PsA (278 pg/mL, range 132 to 642 pg/mL) (P = 0.005) (Table 2). This evidence concerns the gene PRF1 and Behcet disease.