Numerous diseases have been linked to the production of effector cells. The present invention relates to the realization that effector cells are cycling in these diseases. In addition, the present invention relates to the determination that regulator cells are cycling in degenerative diseases. Based on these realizations, the present invention provides methods for treating conditions such as autoimmune diseases, degenerative diseases, and graft-versus-host disease. The present invention also relates to methods of determining when therapy should be administered to a patient.