CD28 and neoplasm: Quantitation of residual tumor cells compared with pre-coculture numbers at an E:T ratio of 1 : 5 revealed that the number of MCF-7 cells cocultured with NT cells was significantly increased over time, whereas the second-generation CAR MUC1 containing either the 41BB or CD28 endodomain was able to control MCF-7 cell growth (Figure 4(c)).