Alemtuzumab is a CD52-specific monoclonal antibody that markedly depletes T and B lymphocytes and inhibits relapsing multiple sclerosis (MS). However, polymorphonuclear neutrophils also express CD52 and can be depleted by alemtuzumab, thereby potentially contributing to the infections that develop post-alemtuzumab treatment. Surprisingly, however, the degree of neutrophil depletion in MS was not included in the pivotal trial reports.