Flotation-Based T Cell Isolation, Activation, and Expansion from Human Peripheral Blood Mononuclear Cell Samples Using Microbubbles

The process of isolating T cells from peripheral blood mononuclear cells (PBMCs) to establish ex vivo cultures is crucial for research, clinical testing, and cell-based therapies. In this study, a simple, novel protocol to isolate, activate, and expand T cells from PBMCs ex vivo is presented. This study utilizes functionalized buoyancy-activated cell sorting (BACS) technology to isolate and activate T cells. Briefly, the protocol involves the positive selection of CD3⁺ cells from leukopak-derived PBMCs, followed by a 48 h co-stimulation with pre-conjugated anti-CD28-bound streptavidin microbubbles (SAMBs) prior to transduction in 24-well plates. Functionalized microbubbles offer a unique opportunity to buoyantly activate cells, leading to proliferative phenotypes that allow for expansion with minimal exhaustion. This technique offers reduced exhaustion because the co-stimulatory microbubbles remain buoyant and return to the top of the culture medium, thus reducing the amount of time that the expanding cells are in contact with the co-stimulatory factors. The results indicate that the isolated and cultured T cells receive enough stimulation to activate and proliferate but not to an extent that leads to overactivation, which then leads to exhaustion, as demonstrated by the presence of excessive PD-1.