Patent ID: 8304203

Claim:
A method for assaying a human blood-cell sample to determine the concentration of CD4+ T-lymphocytes in the sample, comprising: (a) adding to a human blood-cell sample containing CD4+ T-lymphocytes, heavy dense particles having surface-bound binding agent capable of specific high-affinity attachment to a CD4 antigen, and being effective to specifically react with and bind to cells having CD4 surface antigen, including CD4+ T-lymphocytes, to increase the density of the dense particle-bound cells, and magnetic particles having immobilized thereto surface-bound binding agent capable of specifically binding to CD14 surface antigen, and being effective to specifically react with and bind to cells having a CD14 surface antigen, to increase the magnetic susceptibility of the magnetic particle-bound cells, (b) removing cells containing CD14 surface antigen and magnetic particles from the sample by application of a magnetic field to the sample, (c) causing the dense particle-bound CD4+ T-lymphocytes and dense particles in the sample to migrate through a microchannel column containing the selected medium, by subjecting the sample to a gravitational or centrifugal force for a period of time sufficient to cause substantially all of the dense particle-bound CD4+ T-lymphocytes and dense particles, but not non-particle bound cells, to migrate through the selected medium toward the bottom of the column that indicates CD4+ T-lymphocyte column volumes corresponding to one or more selected blood-sample concentrations of CD4+ T-lymphocytes between 200 and 750 cells/ul blood cells, and (d) inspecting the column to detect cell levels within the column and determine the concentration of CD4+ T-lymphocytes in the sample, based on the volume of cells that migrated through the selected medium toward the bottom of the tube.