Lactoferrin receptors in normal and leukaemic human blood cells

The binding of 125I-lactoferrin to a variety of peripheral blood cells was examined. In the concentration range from 10(-9) mol/l to 10(-6) mol/l a receptor-like binding of lactoferrin was observed in monocytes as well as in polymorphonuclear leucocytes. At the low concentrations of lactoferrin in plasma (about 10(-9) mol/l) the cellular binding to monocytes was about 10 times higher than the binding to polymorphonuclear leucocytes and lymphocytes. A major result from a kinetic analysis was a lower apparent binding affinity to polymorphonuclear leucocytes (KD about 2 X 10(-7) mol/l) than to lymphocytes and monocytes (KD about 2 X 10(-8) mol/l). Studies in leukaemic cells showed that lymphocytes from patients with chronic lymphocytic leukaemia bound lactoferrin to the same small extent as normal lymphocytes. In contrast, a larger component of binding with high affinity (KD about 2 X 10(-8) mol/l) could be demonstrated to lymphoblasts as well as to myeloblasts.