Label-free detection of ConA-induced T-lymphocyte activation at single-cell level by microfluidics.

Lymphocyte activation is critical in regulating immune responses. The resulting T-cell proliferation has been implicated in the pathogenesis of a variety of autoimmune diseases, such as SLE and rheumatoid arthritis. ConA (concanavalin A)-induced activation has been widely used in the T lymphocytes model of immune-mediated liver injury, autoimmune hepatitis, and so on. In those works, it usually requires fluorescent labeling or cell staining to confirm whether the cells are transformed successfully after medicine treatment to figure out efficacy/pharmacology. The detection preparation steps are time-consuming and have limitations for further proteomic/genomic identifications. Here, a label-free microfluidic method is established to detect lymphocyte activation degree. The lymphocyte and ConA-activated lymphocyte were investigated by a microfluidic device. According to where single cells in the sample were captured in the designed channel, lymphocyte and ConA-activated samples are differentiated and characterized by population electric field factors, 2.08 × 10⁴ and 2.21 × 10⁴ V/m, respectively. Furthermore, salidroside, a herbal medicine that was documented to promote the transformation, was used to treat lymphocyte cells, and the treated cell population is detected to be 2.67 × 10⁴ V/m. The characterization indicates an increasing trend with the activation degree. The result maintains a high consistency with traditional staining methods with transformed cells of 15.8%, 28.8%, and 48.3% in each cell population. Dielectrophoresis is promising to work as a tool for detecting lymphocyte transformation and medical efficacy detection.