Assessing the Induction of Long-term Immune Regulation Following Treatment With Lemtrada® (Alemtuzumab).

In this study the investigators wish to test the hypothesis that treatment with Lemtrada is associated with alterations in immune homeostasis in favor of multiple regulatory leukocyte populations which persist long after completion of the treatment phase. Specifically, the investigators propose that regulatory B-cells are induced rapidly following the first course of treatment with Lemtrada, that this occurs prior to induction of other regulatory populations, and that these cells are functionally capable of regulating immune responses. The investigators also propose that there is a concomitant induction of functional regulatory T-cells and alternatively-activated monocytes during the first year after treatment giving a "blanket" enhanced regulatory immune profile. This study is designed primarily to identify possible mechanisms by which Lemtrada acts to modify the immune environment in recipient patients, as such the "outcome" measures are all immunological.