Tumour minicells: single, large vesicles released from cultured mastocytoma cells

We describe a new type of cell fragmentation in P815Y mastocytoma cells yielding one, large, enucleated 'minicell' at a time per parent tumour cell. These tumour minicells (TMC) arise spontaneously in semi-synthetic medium during early stationary phase of the growth curve. Their diameter comprises 21-30% of that of the parent cell line. Separated from parent tumour cells, they are non-tumorigenic. TMC can induce cytotoxic T cell activity against the parent tumour cell line greater cytotoxicity being observed against the P815Y line than an H-2-identical line, L1210. TMC may provide a new tool adaptable to the study of host-tumour relationships, cell size regulation or the mechanistic aspects of cell membrane function.