Obtain large numbers of single-donor mononuclear cells (PBMCs) from normal peripheral blood. Leukopaks are highly concentrated, low-volume apheresis collections, with Institutional Review Board (IRB)- or Research Ethics Committee (REC)-approved consent forms and protocols. Each leukopak is produced from ~2 - 3x blood volumes using the Spectra Optia Apheresis System, with acid-citrate-dextrose solution A (ACDA) as anticoagulant. High-resolution HLA typing (Class I and II alleles and CMV status), and additional donor specifications may be available upon request. Products sold in North America are collected in the US and IRB-approved. Products sold in the UK and EU are collected in the UK at an Human Tissue Authority (HTA) licensed facility, using consent forms and protocols approved by an REC. US donors are screened for HIV-1, HIV-2, hepatitis B, and hepatitis C. UK donors are additionally screened for HTLV I/II and syphilis. Certain products are only available in select territories.