Abstract: A flow cytometry method for reproducibly detecting and counting a lymphocyte population of interest in a leukocyte suspension or whole blood sample in which the red cells are subsequently lysed. The suspension (or sample) is combined with a reagent comprising a primary antibody, either native, carrying an attached enzyme or biotin or other label, and a fixative reagent, in either order. Where the enzyme is not attached, an enzyme is coupled specifically to the primary antibody. The fixed suspension is reacted with a color-producing enzyme-cytochemical reagent. The suspension, now including stained and unstained fixed cells, is passed through a flow cytometer and the cells are characterized and counted on the basis of their light-scattering and light-absorbing properties.

Abstract: The present invention relates to apparatus and method for separating, by centrifugation, blood lymphocytes from other leukocytes in a blood sample. Small dense particles, either wetted or suspended in a physiological, hydrophilic medium, and a chemically inert hydrophobic barrier material are initially located in a suitable container. When the blood sample is added to the container, the particles are phagocytized by the monocytes and granulocytes, so as to increase their specific gravities. Upon centrifugation, the barrier material, whose specific gravity is only slightly greater than the specific gravity of the lymphocytes and less than the respective specific gravities of the phagocytic cells which have ingested particles and of the erythrocytes (red blood cells) in the blood sample, forms a rigid barrier therebetween, allowing harvesting of the lymphocytes, substantially free of contamination.