# Critical Evaluation: C1q-Mediated Synaptic Pruning Hypothesis
## Overview
The hypothesis presents an elegant mechanistic framework linking amyloid oligomers to complement-driven synaptic loss, with therapeutic translation via ANX005. While the molecular pathway is biologically plausible and supported by experimental data, the theoretical analysis contains significant weaknesses that warrant scrutiny.
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## 1. Causal Direction Remains Unresolved
The hypothesis assumes C1q upregulation **drives** synaptic loss in AD. However, C1q has established roles in synaptic **maintenance** and protection (Christina 2017, PMID 28754475). C1q deposition on stressed synapses may represent a compensatory clearance mechanism rather than a primary pathogenic driver. The critical question—whether blocking C1q preserves synapses or impairs necessary physiological pruning—has not been definitively resolved. Human postmortem data showing C1q elevation cannot distinguish cause from consequence.
**Missing evidence**: Longitudinal studies tracking whether C1q elevation precedes or follows measurable synaptic dysfunction in humans.
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## 2. Activity-Independence Claim Is Overstated
The theoretical analysis distinguishes AD pruning as "activity-independent" from developmental pruning, but this distinction lacks rigorous support. Classical complement components (C1q, C3) are **essential** for developmental synapse elimination—C1q deficiency causes ectopic synaptic connectivity (Bialas & Stevens 2013). If C1q operates identically in both contexts, the mechanistic distinction collapses. The "phosphatidylserine exposure" tag may not reliably confer selectivity