Methods for regulating T cell function in a subject, particularly regulatory T cell activity are provided. Methods of the invention include administering to a subject a therapeutically effective amount of an Interleukin 35-specific binding agent, such as an antibody or small molecule inhibitor. The invention further provides methods for enhancing the immunogenicity of a vaccine or overcoming a suppressed immune response to a vaccine in a subject, including administering to the subject a therapeutically effective amount of an IL35-specific binding agent and administering to the subject a vaccine. In one embodiment the vaccine is a cancer vaccine.
