1. Intermittent B cell depletion with rituximab re-dosing upon B cell return: Subjects will not receive their regularly-scheduled every-six-month dose of rituximab and will instead receive rituximab 1000 mg IV x 2 doses (spaced 2-3 weeks apart) once peripheral B cells return ( ≥ 10 B cells/mm3). This cycle will then re-start. Subjects will be seen in clinic every three months.