Two scientists recently developed a hand-held sensor that checks the health of a patient's immune system, including HIV, in seconds.
The sensor checks the quantity of immune cells called CD4+ cells in the blood. A gradual depletion of these cells, which orchestrate the immune response to tumors and infections is believed to be convincing evidence that a patient has HIV, as reported by the magazine New Scientist.
To make the device, researchers from Cornell University and the University at Albany coated electrodes with antibodies specific to CD4+ cells. When a small sample of blood is put onto a chip bearing these electrodes, the antibodies grab hold of the CD4+ cells. The captured cells then impede the flow of current across the electrodes, allowing the density of CD4+ cells to be calculated.
To check that only CD4+ cells were sticking to the electrodes the team added a label to blood samples consisting of a fluorescent dye tagged to a further set of antibodies specific for CD4+ cells. They then used an electron microscope to check which cells had been captured. By counting the captured cells, the researchers devised a scale linking electrical resistance with the density of cells in the blood.