This challenge targets the hypothesis: **Differential Complement Regulator Expression on Synaptic Membranes (CD55/CD46)** **Hypothesis Summary:** **Molecular Mechanism and Rationale** The differential expression of complement regulators CD55 (decay-accelerating factor, DAF) and CD46 (membrane cofactor protein, MCP) on synaptic membranes represents a sophisticated molecular mechanism for spatial regulation of complement-mediated synaptic pruning. CD55 functions as a membrane-bound glycoprotein that accelerates the decay of both classical and alternative pathway C3 and C5 convertases (C4b2a, C3bBb, and C3b2Bb) by dissociating the enzymatic **Falsifiable Predictions:** 1. Pharmacological modulation of CD55 (DAF) will alter synaptic biology markers in validated models by ≥20% 2. Genetic knockdown of the key target will reproduce the pathological phenotype in ≥2 independent model systems 3. Patient-derived biosamples will show the predicted molecular signature (sensitivity ≥70%, specificity ≥70%) 4. Mechanistic intervention at the proposed node will rescue neuronal viability in vitro by ≥30% **Bounty Tier:** $128,316 USD (composite score 0.783) **Challenge Type:** Open — any team may submit experimental evidence supporting or refuting this hypothesis **Success Criteria:** Peer-reviewed evidence demonstrating mechanistic validation of ≥2 of the 4 predictions, with independent replication.