The Impact of Immune Cell-derived Exosomes on Immune Response Initiation and Immune System Function.

Exosomes are small extracellular vesicles that pass genetic material between various cells to modulate or alter their biological function. The role of exosomes is to communicate with the target cell for cell-to-cell communication. Their inherent characteristics of exosomes, such as adhesion molecules, allow targeting specifically to the receiving cell. Exosomes are involved in cell to cell communication in the immune system including antigen presentation, natural killer cells (NK cells) and T cell activation/polarisation, immune suppression and various anti-inflammatory processes. In this review, we have described various functions of exosomes secreted by the immune cells in initiating, activating and modulating immune responses; and highlight the distinct roles of exosomal surface proteins and exosomal cargo. Potential applications of exosomes such as distribution vehicles for immunotherapy are also discussed.

Unfolded protein response-mediated modulation of mesenchymal stem cells.

The endoplasmic reticulum (ER) receives unfolded proteins predestined for the secretory pathway or to be incorporated as transmembrane proteins. The ER has to accommodate the proper folding and glycosylation of these proteins and also to properly incorporate transmembrane proteins. However, under various circumstances, the proteins shuttling through the ER can be misfolded and undergo aggregation, which causes activation of the unfolded protein response (UPR). The UPR is mediated through three primary pathways: activating transcription factor-6, inositol-requiring enzyme-1 (IRE1), and PKR-like endoplasmic reticulum kinase, which up-regulate ER folding chaperones and temporarily suppress protein translation. The UPR can be both cytoprotective and/or cytotoxic depending on the duration of UPR activation and the type of host cell. Proteostasis controls stem cell function, while stress responses affect stem cell identity and differentiation. The present review aimed to explore and discuss the effects of the UPR pathways on mesenchymal stem cells.