In fact, the risk and the type of infection could be different according to indications and doses; its association with chemotherapy, the concomitant administration of immunosuppressive drugs, the characteristics of CLL itself can greatly change the severity of immunodepression, favouring those particular opportunistic infections associated with a low CD4 cell level.42 A rapid decrease in normal and malignant lymphocytes is readily apparent within a few weeks of alemtuzumab administration, with T-cells depression after 4 weeks of treatment. This evidence concerns the gene CD4 and B-cell chronic lymphocytic leukemia.