Extracellular vesicles (EVs) can be divided into two types according to their sources.

Figure 1: Heterogeneity of extracellular vesicles

Table 1 Types of extracellular vesicles

EVs are involved in multiple homeostatic processes, including rapid removal of unnecessary molecules from cells, maturation of cells and rapid adaptation to environmental changes, and activation of coagulation

Innate immunity and inflammation

All immune cell types involved in inflammation can secrete EVs, which in turn play multiple roles in the inflammatory process

In sepsis, EVs have been shown to have pro- and anti-inflammatory effects

Notably, soluble mediators of innate immunity also have important EV-related functions

These examples demonstrate that EVs can exert stimulatory effects through mediators (bioactive lipids, acute phase proteins, and cytokines), danger signals, transfer that affect innate immune cell activation, differentiation or polarization, recruitment, cytokine production, and various other effector functions.

adaptive immunity

lymphocyte development

EVs are thought to have an important role in T cell development, and most thymic EVs are released by thymic epithelial cells

Figure 2: The role of extracellular vesicles in antigen presentation

Demonstration of the antigen-presenting capacity of EVs is the first milestone discovery showing that EVs may have an important role in acquired immunity

immune synapse

EVs have been shown to participate in the function of the immune synapse formed between lymphocytes and APCs

Immunomodulatory

Many molecules known to be involved in immune regulation were found on the surface of EVs, including the immune checkpoint molecules cytotoxic T lymphocyte antigen 4 (CTLA4) and programmed death ligand 1 (PDL1), the apoptosis-inducing ligand FASL (also known as CD95L) and the extracellular enzymes CD39 and CD73 that generate the immunosuppressive adenosine from ATP57

Figure 3: Immunomodulatory functions of extracellular vesicles

The therapeutic potential of EVs has been a hotspot of research over the past few years

Table 2.

Importantly, EVs can also be used in vaccine formulations

Recently, EVs derived from chimeric antigen receptor (CAR) T cells have also attracted widespread attention