With this technical advance, live-cell based SMFS measurements may potentially revolutionize immunotherapies. For example, antibody-based immunotherapies, including monoclonal antibodies (mAbs) blocking the ligand binding of immune checkpoint receptors, bispecific antibodies, and chimeric antigen receptor (CAR) T cells, have efficiently boosted cancer therapy (June
et al.
2018; Labrijn
et al.
2019; Pardoll
2012). One of the bottlenecks impeding accurate prediction of the clinical efficacies of these antibody-based immunotherapies is the inconsistence between the binding kinetics derived from purified proteins based assays (
e.
g., SPR) and functional/clinical outcomes (An
et al.
2020; Drent
et al.
2019; Ghorashian
et al.
2019). For example, CAT CAR, whose solution-based binding affinity to CD19 is >40-fold lower than that of FMC63 CAR in SPR measurements, has significantly stronger cytotoxicity to CD19-expressing cell line and better clinical outcome (Ghorashian
et al.
2019), potentially indicating the requirement of live cell in the kinetic measurements. More importantly, in the following circumstances: (1) potential capture of monoclonal antibodies by Fcγ receptors expressed on myeloid cells (An
et al.
2020; Arlauckas
et al.
2017) (
Fig. 2A), (2) bispecific antibodies physically connect two receptors on opposing cell membranes (de Gast
et al.
1995; Brinkmann and Kontermann
2021) (
Fig. 2B), and (3) CAR-T recognition of antigenic molecules on target cells (Li et al.
2020; Porter
et al.
2016) (
Fig. 2C), biomechanical force generated from membrane tension, from cytoskeleton and from cell migration inevitably impose regulatory effects on antibody–antigen binding kinetics. In this consideration, the mechanically ultra-stable BFP technique has excellent potentials in immunotherapeutic applications, such as characterizing the force-regulated antibody–antigen binding kinetics on live cells to provide physiological-relevant biophysical parameters and optimize therapeutic efficacies (An
et al.
2020).