CD274 and keratoconus: We found that inhibition of PD-L1 in co-cultures of effector and target cells had little effect on killing of non-transgenic KC (Figure 5A; p=0.15 untreated c.f. anti-PD-L1 in B6KC), but promoted killing of KC expressing E7, suggesting up regulation of PD-L1 as a result of E7 expression contributes to resistance to CD8 T cell killing (Figure 5A; p=0.016 E7 c.f. B6; p=0.03 untreated c.f. anti-PD-L1 in E7KC).