Schematic of risk of infection vs TSAT, with values given as indicative of <5th and >95th centile, based on Mottelson et al. At low TSAT, driven by iron deficiency, immune dysfunction (colorless cells) may lead to infection susceptibility. At higher TSAT or unregulated plasma iron concentrations, potentially caused by homozygosity for HFE C282Y, increased iron availability may favor pathogen outgrowth despite iron supply to immune cells. Stable and regulated TSAT in the normal range is associated with immune control of infection.