Specific for human transferrin complex between transferrin and soluble transferrin receptor (N-terminal domain, Kd=2.85 x 10-11 M). Can be used for detection of transferrin in serum by sandwich immunoassay; for detection of transferrin - transferrin receptor complex by sandwich ELISA. Inhibit proliferation of Con-A stimulated peripheral blood lymphocytes; works in indirect immunofluorescence on fixed, paraffin embedded human brain tissue.