Aging enhances release of exosomal cytokine mRNAs by Aβ 1‐42 ‐stimulated macrophages

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Amyloid-β1-42 (Aβ) peptide effects on human models of central nervous system (CNS)-patrolling macrophages (Ms) and CD4 memory T-cells (CD4-Tms) were investigated to examine immune responses to Aβ in Alzheimer's disease. Aβ and lipopolysaccharide (LPS) elicited similar M cytokine and exosomal mRNA (ex-mRNA) responses. Aβ- and LPS-stimulated Ms from 20 ≥65-yr-old subjects generated significantly more IL-1, TNF-α, and IL-6, but not IL-8 or IL-12, and significantly more ex-mRNAs for IL-6, TNF-α, and IL-12, but not for IL-8 or IL-1, than Ms from 20 matched 21- to 45-yr-old subjects. CD4-Tm generation of IL-2, IL-4, and IFN-γ and, for young subjects, IL-10, but not IL-6, evoked by Aβ was significantly lower than with anti-T-cell antigen receptor antibodies (Abs). Abs significantly increased all CD4-Tm ex-mRNAs, but only IL-2 and IL-6 ex-mRNAs were increased by Aβ. There were no significant differences between cytokine and ex-mRNA responses of CD4-Tms from the old compared to the young subjects. M-derived serum exosomes from the old subjects had significantly higher IL-6 and IL-12 ex-mRNA levels than those from the young subjects, whereas there were no differences for CD4-Tm-derived serum exosomes. An Aβ level relevant to neurodegeneration elicited broad M cytokine and ex-mRNA responses that were significantly greater in the old subjects, but only narrow and age-independent CD4-Tm responses.