To test if prophylactic anti-B-cell therapy (weekly rituximab) given within 60 to 90 days after allogeneic transplantation will decrease allogeneic donor B-cell immunity and possibly the incidence of chronic graft-vs-host disease (cGvHD).
To determine if rituximab administered after allogeneic transplantation decreases the incidence of chronic graft-vs-host disease (cGvHD)