Leukopaks® provide enriched peripheral blood mononuclear cells (PBMC) from a single donor with low granulocyte and red blood cells as compared to buffy coats obtained from density gradient centrifugation of whole blood. This highly enriched PBMC fraction requires minimal downstream processing (i.e. Ficoll, RBC lysis, etc.) and can be used directly for isolating high-yields of immune cells, such as CD4+ T cells, CD8+ T cells, CD19+ B cells, monocytes, and a variety of other immune cells and subsets. This allows researchers greater reproducibility of experiments from a single donor (minimizing donor-to-donor variation), a decrease in same cell variability, and scalability of experiments from a single cell type. In addition, up to 12 Leukopak collections can be performed on the same donor in a given year, providing an ample amount of PBMCs for large-scale experiments and research studies.