This iron restriction strategy, known as “iron withholding,” is one of the core mechanisms of nutritional immunity.[22] This includes the regulation of hepcidin: during bacterial infection, the host upregulates the expression of hepcidin, which inhibits the function of the iron transporter ferroportin, reducing iron absorption in the intestine and the release of iron from the reticuloendothelial system. The gene discussed is HAMP; the disease is bacterial infectious disease.