Natalie J. Serkova1, Brian A. Larsen2, Brandon Renner3, Kendra M. Hasebroock1, Erica L. Bradshaw-Pierce1, Michael Holers3, Conrad Stoldt4, Joshua M. Thurman3
1Anesthesiology, University of Colorado Health Sci, Aurora, CO, USA; 2Mechanical Engineering, University of Colorado Boulder, Boulder, CO, USA; 3Medicine, University of Colorado Health Sci, Aurora, CO, USA; 4Mechanical Engineering, University of Colorado Boulder, Aurora, CO, USA
CR2 (CD21) is a transmembrane protein expressed on immunocompetent cells, which binds the cleavage fragments of C3. In the MRL/lpr model of lupus nephritis, injection with the CR2-conjugated SPIO caused a significant reduction in T2-relaxation times in nephritic kidneys; healthy control mice had no changes in T2 values. Furthermore, the injection of untargeted SPIO particles did not affect the T2-values of the kidneys in MRL/lpr mice. Thus, by conjugating the SPIO nanoparticles with recombinant CR2 protein we have developed a contrast agent that specifically targets the site of complement activation. This method can non-invasively detect active inflammation in immune-complex glomerulonephritis.