This inventions relates to a method of separation and partition of the mononuclear cells from a blood sample which comprises… (a) providing a centrifugation tube;… (b) placing within said tube a thixotropic, gel-like substance and a water soluble density gradient material having a specific gravity higher than that of said gel-like substance;… (c) placing a sample of blood within said tube;… (d) subjecting said tube to a centrifugal force to separate mononuclear cells from other cells in said blood sample and establishing a barrier layer between said mononuclear cells and said other cells consisting of separate layers of said gel-like substance and said water soluble density gradient material.
