Since blockade of PD-L1/CD80 interaction reduced but did not completely remove the inhibitory effect of PD-L1/PD-1 interactions, we expect that administration of antibodies to specifically block PD-L1/CD80 interaction will augment GVL effect in lymphoid tissues while maintaining the protective effect of PD-L1/PD-1 interactions in GVHD target tissues. The gene discussed is CD80; the disease is graft versus host disease.