CD52 and neoplasm: Although the variable and differential CD52 expression in T cell lymphoma tumor cells implies a rational role for anti-CD52 mAb alemtuzumab in the treatment of PTCL, persistent expression of CD52 by the background normal T- and B cell infiltrate limits therapeutic window of anti-CD52 therapy due to potential immuno-suppression, including increased risk of viral and other opportunistic infections [20].