A microdevice for multiplexed detection of T-cell-secreted cytokines

Cytokines are produced by immune cells in response to viral or bacterial pathogens and therefore have significant diagnostic value. The goal of the present study was to develop a miniature device for detection of interleukin (IL)-2 and interferon (IFN)-γ cytokines secreted by a small population of CD4 and CD8 T-cells. Microarrays of T-cell- and cytokine-specific Ab spots were printed onto poly(ethylene glycol) (PEG) hydrogel-coated glass slides and enclosed inside a microfluidic device, creating a miniature (∼3 μL) immunoreaction chamber. Introduction of the red blood cell (RBC) depleted whole human blood into the microfluidic device followed by washing at a pre-defined shear stress resulted in isolation of pure CD4 and CD8 T-cells on their respective Ab spots. Importantly, the cells became localized next to anti-IL-2 and -IFN-γ Ab spots. Mitogenic activation of the captured T-cells was followed by immunofluorescent staining (all steps carried out inside a microfluidic device), revealing concentration gradients of surface-bound cytokine molecules. A microarray scanner was then used to quantify the concentration of IFN-γ and IL-2 near CD4 and CD8 T-cells. This study represents one of the first demonstrations of a microdevice for capturing desired T-cell subsets from a small blood volume and determining, on-chip, cytokine profiles of the isolated cells. Such a microdevice is envisioned as an immunology tool for multi-parametric analysis of T-cell function with direct applications in diagnosis/monitoring of HIV and other infectious diseases.