Abstract Title and References:

The defined aim is clear. This study was performed in clearly to address the findings. The title is informative. References are relevant, recent, referenced correctly and included key studies.

Introduction/Background: The information provided defines what is previously known by outlining the research question.

Methods: Subjects are selected carefully, measured and validated and cited appropriately on previous methods used. These informations are sufficient to replicate. The authors could add in the synaptic enrichment section the final concentration, if any, of synaptic fraction for in-vitro phagocytosis assay.

Results: The results section was meaningful, used appropriate legends and statistical tools for representing the data.

Discussion and Conclusion: In brief, yes. For details please see the following comments.

Overall: Yes, Details below.

Title: Altered synaptic ingestion by human microglia in Alzheimer’s Disease

Overall statement or summary of the article and its findings in your words: Phagocytic functions in microglia are considered to clear protein deposits, inactive synapses and other cellular particles. However, evidence-based report was not prepared previously, particularly from human pathology. In the present study, the authors compared temporal cortex and primary visual cortex from postmortem brain sections of Alzheimer’s disease (AD) and non-demented control volunteers. The findings suggest microglia from AD brain regions had increased synaptic debris in microglia than non-demented controls. Obviously, there was no change in region-specific phagocytosis that suggested a global activation of microglia. Confirmed in-vitro finding, in adult primary microglia phagocytosis assay with synaptic fractions from AD subjects, further suggest a requisite to understand in detail on the phagocytosis in pathophysiology.

Overall strength of the article and what impact it might have in the field: Microglia activations and phagocytosis in the central nervous system pathology is widely appreciated. However, the extent to which the phagocytosis phenomenon supports the pathology, beneficially, and its regulations are to understand the underpinning events are completely unclear. In the present manuscript the authors identified an increase in microgliosis and phagocytosed Syn-1 to a greater extent compared to controls. This study adds strength, from human microglia, to the long existing thought that activated microglia enhance clearance during pathology. Future studies along multidirectional approach likely drives to understand and support drug discoveries for neuropathology.

Specific comments on weakness of the article and what could be done to improve: Major points in the article which needs clarification, refinement, reanalysis, rewrites and/or additional information and suggestions for what could be done to improve the article.

In general, the study is well defined to address the existing debate dispute on activation induced microglia phagocytosis. Couple of investigations had concluded suggesting that activation phenotype in microglia likely impaired phagocytosis. This mini report had clearly defined an increased phagocytosis in AD microglia, using postmortem brain tissue sections and synaptic fragments for in-vitro assay. Addressing the following might improve the definitions.

Q1. Activated phagocytic microglial engulfed more amyloid beta plaques and Syn-I (pre-synapse). Quantified protein levels for Syn-1 and PSD-95 suggested a decrease in Syn-1. It is interesting to know if the reduced Syn-1 levels relate to inactive synapses in Alzheimer’s disease? Comments from authors, no additional experiments required.

Minor points like figures/tables not being mentioned in the text, a missing reference, typos and other inconsistencies.

1. Immunoblots for Syn-I from synaptic fractions might be shown in main figures.
2. Synaptic fractions were diluted to 100mM. It would be helpful if authors could define more, if there was any specific concentration decided to use in the final assay.