CD4 and myeloid sarcoma: This represents a further example of how human activity and trial design, rather than animal studies, probably contributed to the failure to translate.2 Interestingly, however, CD4‐specific mAb were not inert and there was a modest and significant reduction in relapse rate in MS.6 However, despite the suggestion that efficacy was related to T‐cell number;6 maintenance of depleted levels of T cells were not attempted further, until alemtuzumab was used.