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Published on: February 19, 2018
Evidence of collective influence in innate sensing using fluidic force microscopy
Elizabeth J Mulder1, Brittany Moser1, Jennifer Delgado1
1Esser-Kahn Lab, Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL, United States.
Abstract:
The innate immune system initiates early response to infection by sensing molecular patterns of infection through pattern-recognition receptors (PRRs). Previous work on PRR stimulation of macrophages revealed significant heterogeneity in single cell responses, suggesting the importance of individual macrophage stimulation. Current methods either isolate individual macrophages or stimulate a whole culture and measure individual readouts. We probed single cell NF-κB responses to localized stimuli within a naïve culture with Fluidic Force Microscopy (FluidFM). Individual cells stimulated in naïve culture were more sensitive compared to individual cells in uniformly stimulated cultures. In cluster stimulation, NF-κB activation decreased with increased cell density or decreased stimulation time. Our results support the growing body of evidence for cell-to-cell communication in macrophage activation, and limit potential mechanisms. Such a mechanism might be manipulated to tune macrophage sensitivity, and the density-dependent modulation of sensitivity to PRR signals could have relevance to biological situations where macrophage density increases.
Insights
Individual macrophage responses to infection signals are more sensitive in naive cultures. Cell density and stimulation time impact NF-κB activation, suggesting cell-to-cell communication in immune responses.
Area of Science:
- Immunology
- Cell Biology
- Microscopy
Background:
- The innate immune system uses pattern-recognition receptors (PRRs) to detect infection.
- Single macrophage responses to PRR stimulation show significant heterogeneity.
- Existing methods for studying macrophage responses are limited.
Purpose of the Study:
- To investigate single cell NF-κB responses to localized stimuli in naive macrophage cultures.
- To understand how cell density and stimulation time affect macrophage activation.
- To explore mechanisms of cell-to-cell communication in immune responses.
Main Methods:
- Utilized Fluidic Force Microscopy (FluidFM) for localized stimulation of individual macrophages.
- Measured NF-κB activation at the single-cell level within naive and uniformly stimulated cultures.
- Analyzed the impact of varying cell density and stimulation duration on NF-κB responses.
Main Results:
- Individual macrophages stimulated in naive cultures exhibited higher sensitivity compared to those in uniformly stimulated cultures.
- NF-κB activation decreased with increasing cell density during cluster stimulation.
- Reduced stimulation time also led to decreased NF-κB activation in clustered cells.
Conclusions:
- Results indicate cell-to-cell communication influences macrophage activation sensitivity.
- Density-dependent modulation of PRR signal sensitivity is a key finding.
- These mechanisms may be relevant in biological contexts with high macrophage density.
