CD4 and neoplasm: Treatment with the mPD1-Fc-OX40L ARC led to an increase in CD4+ T cell populations in both the tumor (Fig. 5c) and spleen (Additional file 6: Figure S6F), that were enriched for effector T cells (CD4+CD25−) compared with non-effector/Treg (CD4+CD25+ or CD4+FOXP3+) cells.