A study including 20 older healthy adult subjects (≥65 years) and 20 younger healthy adult subjects (21–45 years) indicated that amyloid-β1-42 peptide (Aβ)–the main component of the amyloid plaques found in the brains of patients with Alzheimer’s disease [46] stimulated the release of exosomal cytokine mRNAs via macrophages and CD4 memory T-cells, indicating that exosomal cytokine mRNAs could potentially act as diagnostic biomarkers for Alzheimer’s disease [47]. The gene discussed is CD4; the disease is early-onset autosomal dominant Alzheimer disease.