Provided is directed to the field of immunotherapy. Specifically, provided are compositions and methods for improved T cell modulation ex vivo and in vivo and for the treatment of cancer and other pathologies. More specifically, embodiments of the subject matter are directed to the use of soluble NTB-A polypeptides or agonists thereof for the treatment of cancer patients, for preventing and treating cytopenia in susceptible patients, and for the ex vivo preparation of improved cell compositions.