Phase 1 · Understand the Body — Why the disease behaves the way it does.
The One-Line Truth
The whole disease in one chain
Everything on this page exists to explain this line.
HIV (CD4-driven), transplant (time-based), neutropenic (low white cells), complement (body defense), B-cell.
Security Layers Collapse Unevenly
Imagine a bank with four separate security systems: armed guards at the door (neutrophils), ID checkers inside (complement proteins), vault monitors (B-cells and antibodies), and a central dispatch center (CD4 cells coordinating everything). When the bank cuts one security layer, certain thieves exploit that specific gap—the building does not become equally vulnerable everywhere. Remove the guards and thieves sneak in through the lobby (bacteria and fungi attack). Disable the ID checker and a specific criminal type (Neisseria) slips past. Shut down dispatch and all systems fail because no one is coordinating (HIV destroying CD4). Each broken layer opens a door to different invaders; you identify which door is open by seeing which thieves got through.
IDSA Clinical Practice Guidelines for Opportunistic Infections · CDC Guidelines for Prevention and Treatment of Opportunistic Infections in HIV · NEJM review on infections in immunocompromised hosts · ATS/IDSA Guidelines on Healthcare-Associated Pneumonia · reviewed 2026-07-07