Research Associate Advanced Biomedical instrumentation Centre, Hong Kong
Abstract: Current state-of-the-art in understanding immunological behavior highly relies on proteins induced and exist within immune cells, such as CD markers, cytokines and gene expressions. To confirm immune cell subtypes within a biopsy, such as blood from clinic, immunostaining techniques were applied while further exploration of their functions are often investigated with gene sequencing technologies in addition to previous procedures. Results were satisfactory in terms of accuracy of diagnosis, yet they require well-trained labor force and expensive bioreagents if single-cell analysis is required in these tests. Recently, morphological profiling of immune cell behaviors under various circumstances is suggested to be another potential aspect to categorize relevant differences. Our study demonstrates how multi-ATOM, a label-free imaging flow cytometry system that captures single-cell images with different contrasts in addition to fluorescence signals, was applied to demonstrate the potential of discovering immune cell subtype behavior differences under different conditions. Morphological profile variations such as sizes and surface texture between human CD4+ and CD8+ T cells were revealed when they were in resting states and exposed to activation antigens (anti-CD2/CD28) in different durations, on the scale of 24 hours intervals across activation groups. Other than that, our in-vitro study also suggested the morphological differences between acute activation of human T cells (within 72 hours), chronic activation of human T cells (exposing T cell towards anti-CD3/CD28 beads for 11 days) and resting T cells (supplemented with Il-2 only). With these evidence, it is suggested label-free imaging techniques can be adopted for fast-screening of immune cell activation and exhaustion states, which potentially be further applied to study differentiation of hematopoietic stem cell towards immune cells and relevant clinical applications.
