In neuroinflammatory conditions, intracellular iron appears to fuel the development of pathogenic Th cells by promoting GM-CSF production.7Conversely, iron deficiency hinders B cell proliferation and antibody responses, highlighting its role in regulating humoral immunity and potentially impacting vaccination efficacy.8Recent findings link the production of tetrahydrobiopterin (BH4) in activated T cells to changes in iron metabolism and mitochondrial function. This evidence concerns the gene CSF2 and Iron deficiency anemia.