Exosomes are a particular type of extracellular vesicle, characterized by their 
endosomal origin as intraluminal vesicles present in large endosomes with a 
multivesicular structure. After these endosomes fuse with the plasma membrane, 
exosomes are secreted into the extracellular space. The ability of exosomes to 
carry and selectively deliver bioactive molecules (e.g., lipids, proteins, and 
nucleic acids) confers on them the capacity to modulate the activity of receptor 
cells, even if these cells are located in distant tissues or organs. Since 
exosomal cargo depends on cell type, a detailed understanding of the mechanisms 
that regulate the biochemical composition of exosomes is fundamental to a 
comprehensive view of exosome function. Here, we review the latest advances 
concerning exosome function and biogenesis in T cells, with particular focus on 
the mechanism of protein sorting at multivesicular endosomes. Exosomes secreted 
by specific T-cell subsets can modulate the activity of immune cells, including 
other T-cell subsets. Ceramide, tetraspanins and MAL have been revealed to be 
important in exosome biogenesis by T cells. These molecules, therefore, 
constitute potential molecular targets for artificially modulating exosome 
production and, hence, the immune response for therapeutic purposes.