PDCD1 and Carcinoma, Lewis Lung: To investigate the in vivo efficacy of HA PD-1 Ig for immunotherapy, we used a Lewis lung carcinoma (3LL) model (Chakravarty et al., 1999, Chakravarty et al., 2006, Deb et al., 2001) to evaluate the synergy between HA PD-1 Ig-mediated checkpoint inhibition and radiotherapy (RT) (Fig. 4A).