Restifo et al (2000) have disputed the FasL/Fas tumour ‘counter-attack’ mechanism as being over-simplistic, while others (Zaks et al, 1999) have demonstrated that in tumour–immune cell interactions, lymphocytes initially recognise tumour cells via MHC/T-cell receptor complexes and subsequently upregulate their FasL expression. The gene discussed is FAS; the disease is neoplasm.