Counting CD4+ T Cells By Chemiluminescence

A low-cost, portable device for measuring the number of CD4+ T-lymphocyte cells in blood could significantly improve the management of HIV/AIDS in patients. CD4 is a receptor on the surface of T cells in the immune system, and a CD4+ T-cell count below 200 cells per μL signals the onset of AIDS. Columbia University’s Samuel K. Sia and coworkers are now reporting a microfluidic device that uses chemiluminescence detection to track CD4+ T cells at the clinically significant 200 cells per μL level (Anal. Chem., DOI: 10.1021/ac902144w). “Chemiluminescence detection works without the need of an external light source, which takes us a step closer to the development of a portable diagnostics device with minimal instrumentation,” Sia says. The researchers isolate CD4+ T cells from whole blood by trapping the cells on microfabricated pillars that are coated with anti-CD4 antibody. To avoid measuring monocytes, which also express CD4, they detect the T cells with anti-CD3 antibodies that are conjugated to horseradish peroxidase. The researchers incubate the cells with the chemiluminescent substrates luminol and hydrogen peroxide and then measure the photocurrent produced as a result of the chemiluminescent reaction.