CD28 and glioblastoma: The following chain reaction could occur: cultured cloned glioma cells (IGF-I(+), MHC-I(−), B7(−)) ⇒ cultured transfected anti-gene IGF-I cells (IGF-I(−), MHC-I(+), B7(+)) ⇒ injection (glioblastoma patients) ⇒ induction of CTL CD8(+) CD28(+) ⇒ destruction of injected transfected anti-gene IGF-I cells (IGF-I(−), MHC-I(+), B7(+)), and arrest of a solid glioma tumour (IGF-I(+/−), MHC-I(+), B7(+)) (see also caption of Figure 1).