T Cells have a key function in the adaptive immune system. They can either promote growth and differentiation of other immune cells or show suppressive function and down-regulate immune reactions. These cells are often extracted from whole blood or from leukopacks using ficoll, a hydrophilic polysaccharide that separates layers of blood, with monocytes and lymphocytes forming a buffy coat under a layer of plasma. Samples from each donor are tested via PCR to confirm non-reactivity.
