Binding of C‐reactive protein to human neutrophils

The binding of radiolabelled 125I-CRP to human neutrophils has been characterised according to pH, temperature and time dependence. The binding of 125I-CRP was saturable, very fast (less than 2 min at 22 C), and the labelled protein was displaced by unlabelled CRP and aggregated human IgG. The dissociation constant was 3.2 X 10(-8) M at pH 7.4, 22 degrees C and 8.8 X 10(-8) M at pH 6.0, 22 degrees C. The calculated number of binding sites was 5-20 X 10(4) per cell at pH 7.4, 22 degrees C. An association with an Fc-type receptor is suggested, since aggregated IgG was able to displace specifically CRP.