Which of the Following Is a Correct Description of Checkpoint

Which of the following is a correct description of checkpoint blocker drugs used in tumor immunotherapy?

A) Soluble Ig-fusion proteins that contain the extracellular domains of T cell inhibitory molecules
B) Blocking monoclonal antibodies specific for T cell growth factor IL-2
C) Small molecule inhibitors of JAK kinases involved in cytokine activation of T cells
D) Blocking monoclonal antibodies specific for T cell molecules that normally inhibit T cell activation
E) Blocking monoclonal antibodies specific for T cell molecules that normally enhance T cell activation