Controlled One-on-One Encounters between Immune Cells and Microbes Reveal Mechanisms of Phagocytosis

Heinrich, Volkmar

doi:10.1016/j.bpj.2015.06.042

Cited by 39 publications

(44 citation statements)

References 44 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It demonstrates that although the underlying substrate was only functionalized with BSA and anti-BSA serum protein (i.e., not with specific targets of typical focal adhesion receptors such as fibronectin and collagen), the cells formed strong, stable anchor points. The presence of anchor points along the proximal phagosome surface supports the notion that phagocytosis is driven via a pushand-lock mechanism wherein actin polymerization provides the force necessary to extend the membrane, but the progressive formation of adhesive anchors steers the cell to encapsulate the particle (6).…”

Section: Characteristics Of Frustrated Phagocytosismentioning

confidence: 53%

“…During traditional phagocytosis, J774A.1 cells have been reported to increase their apparent surface area by up to 500-600% before they are no longer able to take up more/larger particles (17). The neutrophil limit is reported to be 300% (6).…”

Section: Estimation Of Tension At the Onset Of Late-stage Contractionmentioning

confidence: 99%

“…It has been well documented that phagocytic spreading is an active process predominantly driven by actin cytoskeleton protrusive forces, akin to the process that drives lamellipodia-based cellular migration (6). In the case of Fc-receptormediated phagocytosis, receptor binding initiates a signaling cascade that culminates in the recruitment of actin polymerization factors (7).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Frustrated Phagocytic Spreading of J774A-1 Macrophages Ends in Myosin II-Dependent Contraction

Kovari

Wei

Chang

et al. 2016

Biophysical Journal

View full text Add to dashboard Cite

Conventional studies of dynamic phagocytic behavior have been limited in terms of spatial and temporal resolution due to the inherent three-dimensionality and small features of phagocytosis. To overcome these issues, we use a series of frustrated phagocytosis assays to quantitatively characterize phagocytic spreading dynamics. Our investigation reveals that frustrated phagocytic spreading occurs in phases and is punctuated by a distinct period of contraction. The spreading duration and peak contact areas are independent of the surface opsonin density, although the opsonin density does affect the likelihood that a cell will spread. This reinforces the idea that phagocytosis dynamics are primarily dictated by cytoskeletal activity. Structured illumination microscopy reveals that F-actin is reorganized during the course of frustrated phagocytosis. F-actin in early stages is consistent with that observed in lamellipodial protrusions. During the contraction phase, it is bundled into fibers that surround the cell and is reminiscent of a contractile belt. Using traction force microscopy, we show that cells exert significant strain on the underlying substrate during the contraction phase but little strain during the spreading phase, demonstrating that phagocytes actively constrict during late-stage phagocytosis. We also find that latestage contraction initiates after the cell surface area increases by 225%, which is consistent with the point at which cortical tension begins to rise. Moreover, reducing tension by exposing cells to hypertonic buffer shifts the onset of contraction to occur in larger contact areas. Together, these findings provide further evidence that tension plays a significant role in signaling late-stage phagocytic activity.

show abstract

Section: Characteristics Of Frustrated Phagocytosismentioning

confidence: 53%

Section: Estimation Of Tension At the Onset Of Late-stage Contractionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Frustrated Phagocytic Spreading of J774A-1 Macrophages Ends in Myosin II-Dependent Contraction

Kovari

Wei

Chang

et al. 2016

Biophysical Journal

View full text Add to dashboard Cite

show abstract

“…In these single live-cell experiments, we use micropipette manipulation and/or optical tweezers to maneuver target particles into the proximity of non-adherent, initially quiescent human neutrophils (17). Microscopic inspection of the resulting neutrophil morphology provides a clear readout of the chemotactic activity of the cells (Figure 2A).…”

Section: Resultsmentioning

confidence: 99%

Analytical Prediction of the Spatiotemporal Distribution of Chemoattractants around Their Source: Theory and Application to Complement-Mediated Chemotaxis

2017

Self Cite

View full text Add to dashboard Cite

The ability of motile immune cells to detect and follow gradients of chemoattractant is critical to numerous vital functions, including their recruitment to sites of infection and—in emerging immunotherapeutic applications—to malignant tumors. Facilitated by a multitude of chemotactic receptors, the cells navigate a maze of stimuli to home in on their target. Distinct chemotactic processes direct this navigation at particular times and cell-target distances. The expedient coordination of this spatiotemporal hierarchy of chemotactic stages is the central element of a key paradigm of immunotaxis. Understanding this hierarchy is an enormous interdisciplinary challenge that requires, among others, quantitative insight into the shape, range, and dynamics of the profiles of chemoattractants around their sources. We here present a closed-form solution to a diffusion–reaction problem that describes the evolution of the concentration gradient of chemoattractant under various conditions. Our ready-to-use mathematical prescription captures many biological situations reasonably well and can be explored with standard graphing software, making it a valuable resource for every researcher studying chemotaxis. We here apply this mathematical model to characterize the chemoattractant cloud of anaphylatoxins that forms around bacterial and fungal pathogens in the presence of host serum. We analyze the spatial reach, rate of formation, and rate of dispersal of this locator cloud under realistic physiological conditions. Our analysis predicts that simply being small is an effective protective strategy of pathogens against complement-mediated discovery by host immune cells over moderate-to-large distances. Leveraging our predictions against single-cell, pure-chemotaxis experiments that use human immune cells as biosensors, we are able to explain the limited distance over which the cells recognize microbes. We conclude that complement-mediated chemotaxis is a universal, but short-range, homing mechanism by which chemotaxing immune cells can implement a last-minute course correction toward pathogenic microbes. Thus, the integration of theory and experiments provides a sound mechanistic explanation of the primary role of complement-mediated chemotaxis within the hierarchy of immunotaxis, and why other chemotactic processes are required for the successful recruitment of immune cells over large distances.

show abstract

“…We applied a single-live-cell, single-target assay (34)(35)(36) to examine intracellular Ca 2+ concentrations during controlled one-on-one encounters between neutrophils-the most abundant type of human white blood cell-and pathogenic surfaces. Our results invite a careful reevaluation of some common assumptions about Ca 2+ signaling in immune cells.…”

Section: Introductionmentioning

confidence: 99%

Extension of chemotactic pseudopods by nonadherent human neutrophils does not require or cause calcium bursts

Francis

Heinrich

2018

Sci. Signal.

Self Cite

View full text Add to dashboard Cite

Global bursts in free intracellular calcium (Ca) are among the most conspicuous signaling events in immune cells. To test the common view that Ca bursts mediate rearrangement of the actin cytoskeleton in response to the activation of G protein-coupled receptors, we combined single-cell manipulation with fluorescence imaging and monitored the Ca concentration in individual human neutrophils during complement-mediated chemotaxis. By decoupling purely chemotactic pseudopod formation from cell-substrate adhesion, we showed that physiological concentrations of anaphylatoxins, such as C5a, induced nonadherent human neutrophils to form chemotactic pseudopods but did not elicit Ca bursts. By contrast, pathological or supraphysiological concentrations of C5a often triggered Ca bursts, but pseudopod protrusion stalled or reversed in such cases, effectively halting chemotaxis, similar to sepsis-associated neutrophil paralysis. The maximum increase in cell surface area during pseudopod extension in pure chemotaxis was much smaller-by a factor of 8-than the known capacity of adherent human neutrophils to expand their surface. Because the measured rise in cortical tension was not sufficient to account for this difference, we attribute the limited deformability to a reduced ability of the cytoskeleton to generate protrusive force in the absence of cell adhesion. Thus, we hypothesize that Ca bursts in neutrophils control a mechanistic switch between two distinct modes of cytoskeletal organization and dynamics. A key element of this switch appears to be the expedient coordination of adhesion-dependent lock or release events of cytoskeletal membrane anchors.

show abstract

Controlled One-on-One Encounters between Immune Cells and Microbes Reveal Mechanisms of Phagocytosis

Cited by 39 publications

References 44 publications

Frustrated Phagocytic Spreading of J774A-1 Macrophages Ends in Myosin II-Dependent Contraction

Frustrated Phagocytic Spreading of J774A-1 Macrophages Ends in Myosin II-Dependent Contraction

Analytical Prediction of the Spatiotemporal Distribution of Chemoattractants around Their Source: Theory and Application to Complement-Mediated Chemotaxis

Extension of chemotactic pseudopods by nonadherent human neutrophils does not require or cause calcium bursts

Contact Info

Product

Resources

About