A rapid redistribution of transferrin receptors to the cell surface of L2C lymphocytes upon fixation of holoform transferrin.

The internalization and recycling kinetics of transferrin receptors in leukemic lymphocytes (L2C) differed in the absence or presence of ligand. At 37 degrees C in the absence of ligand, transferrin receptors were mainly distributed internaly. We demonstrated, using a sepharose-bead-Tf complex, the rapid recycling of unoccupied internal transferrin receptors was correlated with ligand binding to surface receptors. The recycling amplitude was related to the occupancy of iron ligated transferrin to plasma membrane surface receptors. Contrary to the results obtained with other cells, redistribution of Tf receptors was not triggered by binding of other ligands to their receptors.