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Updated: Dec 29, 2025
A Flow Cytometry-Based Cytotoxicity Assay for the Assessment of Human NK Cell Activity
Published on: August 9, 2017
Activation of Lymphocyte Cytolytic Machinery: Where are We?
Ricciarda Galandrini1, Cristina Capuano, Angela Santoni
1Department of Experimental Medicine, Istituto Pasteur-Fondazione Cenci-Bolognetti, Fondazione Eleonora Lorillard Spencer Cenci, Sapienza University , Rome , Italy.
Insights
Cytotoxic lymphocytes form a specialized immune synapse to eliminate target cells. Recent advances reveal molecular mechanisms of granule secretion and synapse remodeling in Natural killer cells and CD8(+) T cells.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- Cytotoxic lymphocytes recognize target cells via receptor engagement, initiating signaling cascades.
- The cytotoxic immune synapse is a dynamic interface crucial for integrating signals and secreting lytic granules.
- Understanding the molecular basis of cytotoxic responses is vital for immune function.
Purpose of the Study:
- To review recent advancements in understanding the molecular mechanisms of cytotoxic machinery activation.
- To explore the dynamics of receptor signaling, synapse remodeling, and granule secretion.
- To compare cytotoxic processes in Natural killer (NK) cells and cytotoxic CD8(+) T cells.
Main Methods:
- Review of recent literature focusing on molecular signaling pathways.
- Analysis of studies utilizing advanced imaging techniques like super-resolution and TIRF microscopy.
- Examination of findings from genetic defect studies impacting cytotoxic responses.
Main Results:
- Significant progress has been made in identifying molecular effectors regulating cytotoxic processes post-receptor ligation.
- Advanced imaging has provided new insights into receptor and signaling molecule reorganization at the lytic synapse.
- The molecular machinery coupling early receptor signaling to late-stage synapse remodeling and granule dynamics is still under investigation.
Conclusions:
- Knowledge of molecular mechanisms governing granule movement and secretion is substantial.
- Further research is needed to fully elucidate the machinery linking early signaling to late synapse remodeling and granule dynamics.
- Similarities and differences in cytotoxic mechanisms between NK cells and CD8(+) T cells are highlighted.
Abstract:
Target cell recognition by cytotoxic lymphocytes implies the simultaneous engagement and clustering of adhesion and activating receptors followed by the activation of an array of signal transduction pathways. The cytotoxic immune synapse represents the highly specialized dynamic interface formed between the cytolytic effector and its target that allows temporal and spatial integration of signals responsible for a defined sequence of processes culminating with the polarized secretion of lytic granules. Over the last decades, much attention has been given to the molecular signals coupling receptor ligation to the activation of cytolytic machinery. Moreover, in the last 10 years the discovery of genetic defects affecting cytotoxic responses greatly boosted our knowledge on the molecular effectors involved in the regulation of discrete phases of cytotoxic process at post-receptor levels. More recently, the use of super resolution and total internal reflection fluorescence imaging technologies added new insights on the dynamic reorganization of receptor and signaling molecules at lytic synapse as well as on the relationship between granule dynamics and cytoskeleton remodeling. To date we have a solid knowledge of the molecular mechanisms governing granule movement and secretion, being not yet fully unraveled the machinery that couples early receptor signaling to the late stage of synapse remodeling and granule dynamics. Here we highlight recent advances in our understanding of the molecular mechanisms acting in the activation of cytolytic machinery, also discussing similarities and differences between Natural killer cells and cytotoxic CD8(+) T cells.
