CD4 and B-cell chronic lymphocytic leukemia: In particular, we found that CD4 is lacking at the neoplastic cell level in up to 50% of cases.27 CD52 is a molecule expressed by most peripheral blood lymphocytes, macrophages, and monocytes.102 Campath-1H (alemtuzumab) is a humanised antibody against CD52 currently approved for B cell chronic lymphocytic leukaemia therapy,103–106 and it has also shown interesting activity in T prolymphocytic leukaemia and cutaneous TCLs.107 Although other factors can affect its response in vivo, the lack of CD52 expression may play a major role in causing refractoriness to the compound.