This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. I. HYPOTHESIS Although the beneficial effects of pre-SCT donor and recipient immunizations have repeatedly been shown in recipients of matched sibling donor (MSD) SCT even after ex vivo T-cell depletion, it is unknown if these effects can be produced in recipients of haploidentical stem cell transplants (in whom there is incomplete matching between donor B cells and recipient antigen presenting cells). Nor is it known whether transfer would be observed after the use of current stem cell preparative regimens, which include monoclonal antibodies such as alemtuzumab (anti-CD52) that are broadly reactive with multiple components of the immune system, and which persist through the peri-transplant period. We wish to confirm that immunization of donor and recipient remains a feasible means of producing antibody responses in stem cell recipients, and discover whether the approach can be extended to recipients of haploidentical stem cell transplantation or to patients who received immune depleting antibodies as part of their preparative regimen. In this pilot study, we will examine the transfer of antibody recall responses to tetanus toxoid, since this immunogen has been safely and widely used for many decades. If effective, we will develop additional studies to use immunization of greater therapeutic utility for the transplant recipient, including those for pneumococcal and hepatitis B antigens. Because of the nature of this study, we will only be able to include donors that are related to the recipient so that the donors are available for tetanus injection pre-harvest. II. SPECIFIC AIMS The purpose of this protocol is to determine antibody recall responses in patients receiving allogeneic hematopoietic stem cell transplants. The primary objective is to determine the time to detect antibody recall response during the first 12 months after SCT. In addition to, determining immunoglobulin levels before, during, and after SCT.