Exosomes: An emerging factor in stress-induced immunomodulation

• Stressor exposure modifies exosome protein and microRNA composition.
• Modified exosomes can regulate in vivo immunity.
• Blood exosomes may enable long-distance cellular communication and obviate the need for direct cell-to-cell contact.

Cells constitutively release small (40–100 nm) vesicles known as exosomes, but their composition and function changes in response to a variety of physiological challenges, such as injury, infection, and disease. Advances in our understanding of the immunological relevance of exosomes have been made, however, few studies have explored their role in stress physiology. Exposure to a variety of acute stressors facilitates the efficacy of innate immune responses, but the mechanisms for these effects are not fully understood. Since exosomes are emerging as important inflammatory mediators, they likely exhibit a similar role when an organism is exposed to an acute stressor. Here, we review our current knowledge of the basic properties and immunological functions of exosomes and provide emerging data supporting the role of stress-modified exosomes in regulating the innate immune response, potentially enabling long-distance cellular communication and obviating the need for direct cell-to-cell contact.