PRF1 and neoplasm: Sundstedt et al (1998) showed that injection of staphylococcal enterotoxin A into perforin-deficient mice led to less depletion of B-cells than in control mice. This depletion was due to the release of perforin by CD8+ T cells. In GvL and GvH reactivity, a role for both systems (granule exocytosis as well as CD95/CD95L) was reported (Miwa et al, 1999; Yasukawa et al, 2000). It was thus of interest to elucidate the mechanism by which allogeneic Vβ6+ T cells kill vSAG7+ tumour cells.