CTLA4 and neoplasm: Additionally, intratumor immunosuppressive mediators produced by myeloid-derived suppressor cells (MDSCs), DCs, M2-macrophages, Tregs, or Bregs, glucocorticoids regenerated from inactive metabolites by the tumors themselves, and cell surface checkpoint molecules and their ligands such as PD-1, PD-L1, TIM3, and CTLA4 can all contribute to an ineffective anti-tumor immune response.41