<qa>  What is the purpose of the study?Blood will be obtained from subjects every two weeks and examined in our research laboratories to obtain more information about IVIgs biological effects. Cerebrospinal fluid will be obtained by lumbar puncture twice over the course of the study for the same purpose. Patients will be asked to allow a portion of a blood sample to be used for Apolipoprotein E APOE testing and banked for genetic research testing related to AD and aging, but do not have to participate in the testing or allow their blood sample to be stored in order to take part in the study. 