The percentages of CD4+ T cells within the bulk MEAMNC population by culture termination were at relatively equal levels (33 and 47%), with those in bulk cultures sensitised by ACE from the HER-2/neu+ primary tumours Ova-1, Ova-2 and Ova-3, thus excluding the possibility that low numbers of CD4+ T cells, apparently providing insufficient help for CD8+ CTL, could account for the low cytotoxic responses against the autologous primary tumour cells or the tumour cell lines. This evidence concerns the gene ACE and neoplasm.