The present disclosure provides improved compositions for adoptive T cell therapies for treating, preventing, or ameliorating at least one symptom of a cancer, infectious disease, autoimmune disease, inflammatory disease, and immunodeficiency, or condition associated therewith.

Provided herein are proteins, antibodies, assays and methods useful for modulating growth factor levels and/or activities. In some embodiments, such growth factors are members of the TGF- superfamily of proteins.