Cell-Target Interactions

Part of: Immunology

Cell–cell interactions: Quantifying cellular binding strength and isolating potent
lymphocytes from a heterogeneous cell population

In this proof of concept, researchers cultured a target cell line inside the z-Movi Chip and introduced three lymphocyte populations with high affinity (red), intermediate (green) and low affinity (cyan) against the target cell line.

Next, a force ramp was applied. At the low force regime, the low affinity lymphocytes were separated from the mixed population, resulting in an enriched target-specific lymphocyte population inside the chip. By increasing the force further we quantified the binding strength of each class of lymphocytes (Figure 1), but also screened and collected lymphocytes based on their target cell avidity.

In these types of experiments, it becomes possible to identify, examine, collect, and ultimately expand for further research the most potent cells. As the z-Movi uses non-invasive forces to probe cells, their viability is not affected, enabling us to perform further analysis to the collected enriched cell population fractions, such as sequencing, mass spectrometry, flow cytometry, and functional (cytotoxicity) assays.

1 Compared avidity of the three lymphocyte populations against the target cell.

Cell–cell avidity enhanced by antibodies: Screening of bispecific antibodies

Screening of therapeutic antibodies that enhance the killing properties of the T cells is crucial for the development of immunotherapies against cancer or other diseases. With the z-Movi we can determine the effect of the bispecific antibody on T cell binding to target tumor cells.

In this pilot study, we investigated the interactions of bispecific antibodies bound to T cells against target tumor cells.

Figure 1 shows the total number of T cells bound to tumor cells under increasing applied forces, in the presence and absence of bispecific antibodies. The results demonstrated that in the presence of the antibodies the interaction strength between T cells and tumor cells was significantly enhanced. Similar experiments can be performed to test the selectivity and efficiency of different compounds against a target and determine the compound with the highest binding enhancing properties.

1 Compared avidity of T cells against tumor cells in the presence (blue) and absence of bispecific antibodies (red).

Cell–extracellular matrix interactions: Unraveling the kinetics and strength of cellular adhesion

The z-Movi is a useful tool to obtain insights into the cell adhesion process. Here, Kamsma et al. used the z-Movi to resolve the adhesion forces and kinetics
of CD4+ T lymphocytes (CD4) to fibronectin.

They identified three interaction states of the cells: unbound, binding, and bound. Interaction strengths below 30 pN were defined for unbound cells, below 55 pN for transiently binding and crawling cells, and from 55 pN and above for bound cells (Figure 1).

The researchers then investigated how these properties are influenced by interleukin-7 (IL7), the main regulatory cytokine of CD4 cells. The results demonstrated that while IL7 accelerates CD4 adhesion, it does not influence CD4 binding strength (Figures 2 and 3).

1 Cumulative probability distribution plot of the rupture forces shown for unbound, binding, and bound cells, IL7-activated and non-activated.

Figures 1,2,3 were reprinted with permission from Cell Reports, 2018, 24 (11), pp 3008-3016. Copyright 2018 Elsevier.

Kamsma et al. (2018)
Cell Reports

2 (left)Adhesion of CD4 to the fibronectin-functionalized glass, challenged with increasing concentrations of peptide inhibitors (RGD; plain line GRGDS; dashed  ine). This experiment was performed on three different blood donors (error bars denote SEM).

3 (right) Fraction cells bound as a function of time, plotted for non-activated and IL-7-activated CD4 on glass functionalized or not with fibronectin.

Z-movi

The z-Movi™ is the first instrument that enables you to find and collect the most potent immune cells out of a heterogeneous population and quantify their binding strength to their target. All this in a label-free, high throughput, and single-cell manner.

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