Platelet Activation in Immune Responses

Platelet activation is now recognised as a central element in the orchestration of immune and inflammatory processes beyond its classical role in haemostasis and thrombosis. Upon vascular injury or pathogen encounter, platelets undergo rapid shape change, degranulation and surface receptor modulation, enabling them to interact with endothelial cells, leukocytes and plasma proteins. These activated platelets release cytokines, chemokines and growth factors that recruit and instruct innate immune cells such as neutrophils, monocytes and dendritic cells, while also influencing T and B lymphocyte responses. Through specialised pattern recognition receptors, notably toll-like receptors and Fc receptors, platelets directly sense microbial components and immune complexes, triggering effector functions that include pathogen trapping, complement activation and support of neutrophil extracellular trap formation. Importantly, the bidirectional cross-talk between platelets and immune cells contributes to vascular integrity and tissue repair but, when dysregulated, drives thromboinflammation and immunopathology in conditions ranging from sepsis and viral pneumonia to autoimmune disorders and cardiovascular disease. Understanding the molecular circuits of platelet activation has thus opened avenues for targeted interventions that seek to balance host defence with the prevention of excessive clotting and inflammation.

Research from Nature Portfolio

Recent work has demonstrated that during acute influenza A infection platelets internalise viral particles via TLR7, leading to the release of complement component C3. Platelet-derived C3 acts on neutrophils to induce extracellular trap formation and aggregation, revealing a finely tuned platelet–neutrophil axis that enhances pathogen clearance but also increases the potential for thrombotic vascular occlusion in severe viral disease.

Platelet Activation in Immune Responses publication trend

The graph below shows the total number of articles in platelet activation in immune responses across all publications each year (not limited to Nature Index journals).

Technical terms

Platelet activation: The process by which platelets change shape, expose adhesive receptors and release granule contents in response to stimuli.

Neutrophil extracellular traps (NETs): Web-like structures of DNA and antimicrobial proteins expelled by neutrophils to trap and kill pathogens.

Toll-like receptor 7 (TLR7): A pattern recognition receptor that detects viral single-stranded RNA, initiating innate immune signalling cascades.

Complement C3: A central protein of the complement system that opsonises pathogens and promotes inflammation and phagocytosis.

References

1. Platelets: Orchestrators of immunity in host defense and beyond. Immunity (2024).
2. Platelet signaling in immune landscape: comprehensive mechanism and clinical therapy. Biomarker Research (2024).
3. The role of platelets in mediating a response to human influenza infection. Nature Communications (2019).
4. The Era of Thromboinflammation: Platelets Are Dynamic Sensors and Effector Cells During Infectious Diseases. Frontiers in Immunology (2019).