TNF and Alzheimer disease: When exosomes derived from AD neurons and astrocytes were evaluated for their miRNA content, only those from neurons were enriched in miR-21, while sensitization with a cocktail composed by complement component C1q + interleuklin-1 alpha + tumor necrosis factor alpha (C1q + IL-1α + TNF-α), known to induce neurotoxic reactive astrocytosis [44], was required to produce the same result in exosomes from AD astrocytes.