Specific binding of placental acidic isoferritin to cells of the T‐cell line HD‐MAR

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Abstract
Acidic placental isoferritin inhibited the blastogenic response of peripheral human lymphocytes to T‐cell activating lectins. We measured specific binding of radioiodinated placental isoferritin to cells of the T‐cell line HD‐MAR and found specific high‐affinity binding. Binding was faster and more ferritin was bound at 37°C than at 4°C. Displacement experiments indicated that most of the binding occurred at the cell surface. Acidic placental ferritin and isolated H‐type ferritin subunits but not isolated L‐type subunits, competed for the binding. Scatchard plot analysis showed characteristics of a single binding species with a dissociation constant (K d) of 1.3–4.4 × 10−11 M. The results suggest the presence of receptors for acidic isoferritin on T‐lymphocytes and thus, a regulatory role for the acidic ferritin H‐type subunit in T‐cell function.