TIM-2 soaks up ferritin

The TIM (T cell immunoglobulin mucin) proteins have emerged as key regulators of allergic and autoimmune diseases due to their influence on T helper (Th)-1 and Th-2 responses. On page 955, Chen and colleagues show that one member of this family, TIM-2, multitasks as a receptor for H-ferritin, a component of the iron storage protein ferritin.Ferritin was not what the group expected to find when they launched a search for TIM-2 ligands. “Ferritin is not something immunologists think about much,” says senior author William Seaman. Although circulating H-ferritin had been shown to increase during inflammation and to bind to T and B cells, the consequences of these observations were largely unknown.

Chen et al. now show that although TIM-2 is most highly expressed in the liver, the primary iron storage...