Buffy coats of blood from healthy donors (from the Gulf Coast Regional Blood Center, Houston, TX) were used for isolation of PBMCs (human peripheral blood mononuclear cells) by density-gradient centrifugation with Lymphoprep (Nycomed Pharm). All blood samples were anonymized. The use of PBMCs was in accordance with institutional guidelines on human cell research and the approved protocol (Protocol #IBC00000357) by the Institutional Review Board of Houston Methodist Research Institute. Animal experiments in this study were approved and carried out in accordance with protocol (Protocol #AUP-0115-0005) provided by the Institutional Animal Care and Use Committee (IACUC) at Houston Methodist Research Institute. IACUC uses the National Institute of Health (NIH) Guide for the Care and Use of Laboratory Animals, which is based on the U.S. Government Principles for Utilization and Care of Vertebrate Animals Used in Testing, Research, and Training.