Figure. A digital image of whole blood from a 5-month-old boy.2 Tagged CD4 T cells are displayed in yellow; CD8 T cells, in red; and monocytes, in green. The infant's absolute CD4 count, as obtained with the low-cost prototype microchip method, was 2098 cells/μL; his CD4 proportion of T cells, 0.39. Photo by: PLoS Medicine