Abstract: The invention provides a DNA plasmid comprising: (a) a first transcriptional unit comprising a nucleotide sequence that encodes a first polypeptide operably linked to regulatory elements including a first promoter and a first polyadenylation signal; (b) a second transcriptional unit comprising a nucleotide sequence that encodes a second polypeptide operably linked to regulatory elements including a second promoter and a second polyadenylation signal; (c) a third transcriptional unit comprising a nucleotide sequence that encodes a third polypeptide operably linked to regulatory elements including a third promoter and a third polyadenylation signal; and wherein said first, said second and said third promoters are each derived from different transcriptional units; and wherein said first, said second and said third polyadenylation signals are each derived from different transcriptional units.

Abstract: A method of recovering functional human leukocytes from blood filters used to deplete leukocyte content from leukocyte-containing blood-cell suspensions is provided. More particularly, this method involves isolating leukocytes from filters which have been used to purify red blood cells or platelets in isolation from leukocytes by back-flushing the used filters with a hemolysis solution, such as cold ammonium chloride, and collecting the functional human leukocytes.