CD52 and cytomegalovirus infection: CMV viremia is rare in both cohorts and only additional hits to the immune system lead to the high frequency of symptomatic CMV infections observed for instance in CLL patients treated with the humanized monoclonal antibody Alemtuzumab that targets CD52+ leukocytes (CMV-seroprevalence has not been assessed to date in this patient group) [3,45-47].