RECONSTITUTION OF CD8 T-CELLS IS ESSENTIAL FOR THE PREVENTION OF MULTIPLE-ORGAN CYTOMEGALOVIRUS HISTOPATHOLOGY AFTER BONE-MARROW TRANSPLANTATION

Cytomegalovirus (CMV) infection in the period of temporary immunodefic iency after haematoablative treatment and bone marrow transplantation (BMT) is associated with a risk of graft failure and multiple-organ CM V disease. The efficacy of immune system reconstitution is decisive fo r the prevention of CMV pathogenesis after BMT. Previous data in murin e model systems have documented a redundancy in the immune effector me chanisms controlling CMV. CD8 T cells proved to be relevant but not ir replaceable as antiviral effecters. Specifically, in a state of long-t erm in vivo depletion of the CD8 T-cell subset, CD4 T cells were educe d to become deputy effecters controlling CMV by a mechanism involving antiviral cytokines. It is of medical importance to know whether one c an trust in this 'flexible defence' in all clinical settings. It ii de monstrated here that reconstitution of CD8 T cells is crucial for the prevention of fatal multiple-organ CMV disease under the specific cond itions of BMT.