CD28 and neoplasm: Regarding the in vitro antitumor effect on Skrc59 CAIX+/PD-L1+ human ccRCC, we found that all anti-CAIX CAR T cells had a higher cytotoxic activity when compared to the negative control (anti-BCMA CAR), independent of the CD28 or 4-1BB co-stimulatory domain or the secretion of anti-PD-L1 IgG4 at a 25:1 effector cell/tumor cell ratio (E:T) when treated for 24 h (Figure 1F).