The MR1/MAIT cell axis enhances dystrophic neurite development in Alzheimer's disease

Plaques are a hallmark feature of Alzheimer's disease (AD). We found that the loss of mucosal-associated invariant T (MAIT) cells and their antigen-presenting molecule MR1 caused a delay in plaque pathology development in AD mouse models. However, it remains unknown how this axis is impacting dystrophic neurites.

Brain tissue from 5XFAD mice and those that are MR1 deficient (MR1 KO), were analyzed for dystrophic neurites, amyloid plaques, and synapses via immunofluorescence, RNA sequencing, enzyme-linked immunosorbent assay, and western blot.

In 8-month-old 5XFAD/MR1 KO mice, there was reduced expression of lysosomal-associated membrane protein 1, ubiquitin, and n-terminal amyloid precursor protein in the hippocampus compared to 5XFAD mice (P < 0.05). 5XFAD/MR1 KO mice also had less insoluble amyloid beta 40 (P < 0.001) and higher levels of postsynaptic density protein 95 (P < 0.01) in the hippocampus.

Our data contribute additional mechanistic insight into the detrimental role of the MR1/MAIT cell axis in AD pathology development.

5XFAD mice lacking the innate immune MR1/MAIT (mucosal-associated invariant T) cell axis (5XFAD/MR1 KO) have reduced numbers of dystrophic neurite markers in the hippocampus at 8 months of age. Hippocampal tissue transcriptional analyses showed reduced expression of genes encoding classical dystrophic neurite markers in 5XFAD/MR1 KO mice. 5XFAD/MR1 KO mice had less insoluble amyloid beta 40 and increased levels of the post-synaptic marker, postsynaptic density protein 95, in the hippocampus than did MR1+ 5XFAD mice.