CTLA4 and neoplasm: Many different mutually non-exclusive factors can contribute to this situation: (i) lack of antigen release by tumor cells, (ii) inhibition of antigen uptake, antigen presentation, and maturation of DCs, (iii) inhibition of DC migration to the lymph nodes, (iv) inhibition of effective T cell priming through CTLA-4 or Treg in the lymph nodes, (v) inhibition of T cell trafficking from the lymph nodes to the tumor site.