A method of reducing or relieving immune inhibition in a mammal includes the step of at least partly inhibiting or reducing CD96 activity in one or more cells of the mammal to thereby relieve immune inhibition and/or enhance or restore immune surveillance in the mammal. Typically inhibiting or reducing CD96 activity does not include or depend upon killing of CD96 expressing cells in the mammal. The method relieves immune inhibition and/or enhances or restores immune surveillance in the mammal to thereby treat or prevent cancer or cancer metastasis and/or a viral infection in the mammal. Also provided is a method of screening designing engineering or otherwise producing a CD96 inhibitory agent that relieves immune inhibition and/or enhances or restores immune surveillance in a mammal. Typically the CD96 inhibitory agent is an antibody or antibody fragment.
