A 52-year-old man with rheumatoid arthritis on chronic anti-TNF therapy presents with fatigue and dyspnea. Laboratory findings show: hemoglobin 9.2 g/dL, serum iron 35 µg/dL (low), transferrin saturation 18% (low), but ferritin 280 ng/mL (elevated). The structure marked **D** in the diagram is abnormally elevated due to chronic inflammatory cytokine signaling. Which of the following best explains the mechanism by which elevated **D** produces this anemia pattern?