Lactoferrin binds to neutrophilic membrane DNA

Lactoferrin (LF) binding to the surface of human neutrophils was shown to be dependent upon the presence of cell surface DNA by (i) an abrogation of LF binding after treatment of whole cells with DNAse; (ii) an abrogation of LF binding to a purified cell membrane suspension after DNAse digestion, (iii) a restoration of LF binding, after initial treatment of cells with DNAse, by the addition of exogenous DNA. Using a biotinylated LF probe, no other binding molecules were found after SDS PAGE of neutrophil cell membrane proteins. Further evidence of a DNA‐LF interaction was obtained by the co‐isolation of LF with DNA by both gel chromatography and affinity chromatography using Heparin Sepharose CL 6B. The interaction of LF with neutrophils was a saturable phenomenon with a K_d of 6.2 x 10^‐6 M and a maximum binding of 9.2 x 10⁶ molecules per cell. These results suggest that cell membrane DNA may have a novel role as a receptor for LF, and indicates the need for further experiments to determine whether the functional effects of LF are modified by the DNAse treatment of LF responsive cells.