...

flowchart TD
    A["Aging Brain"]
    B["PRC2/EZH2 Decline"]
    C["H3K27me3 Loss at C4b Promoter"]
    D["NF-kappaB Activation"]
    E["IFN-gamma from Microglia"]
    F["C4b Transcription Upregulated"]
    G["C4b Protein on Synapses"]
    H["C3 Convertase Formation"]
    I["C3b Opsonization"]
    J["Microglial Phagocytosis"]
    K["Synaptic Loss in CA1"]
    L["CD46/CD55/CD59 Decline"]
    M["Cognitive Decline"]

    A -->|"epigenetic changes"| B
    B -->|"de-repression"| C
    C -->|"promotes"| F
    A -->|"inflammaging"| D
    D -->|"activates"| F
    A -->|"microglial aging"| E
    E -->|"JAK/STAT1"| F
    F -->|"cleaved C4b"| G
    G -->|"recruits C2"| H
    H -->|"amplifies"| I
    I -->|"tags synapses"| J
    J -->|"eliminates"| K
    A -->|"regulatory decline"| L
    L -->|"removes brakes"| G
    K -->|"drives"| M

    style A fill:#ffd54f,color:#000
    style F fill:#ef5350,color:#fff
    style K fill:#ef5350,color:#fff
    style M fill:#ef5350,color:#fff
    style L fill:#ce93d8,color:#000