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It is assumed that activated neutrophils contribute to the development of anti-neutrophil cytoplasmic auto-antibody (ANCA)-associated vasculitis due to the association of myelopeoxidase(MPO)-ANCA with MPO expressed on the surface of activated neutrophils. FITC-labeled antibody (Ab) used widely are not suitable for neutrophil examination because of the labile fluorescence emission of FITC. Therefore, it is necessary to develop specific fluorescent probes for MPO detection in neutrophils in vivo. Recently, fluorescent nanocrystal quantum dots (QDs) have been used for biotechnological and medical applications because of their greater and far longer fluorescence in. QDs have several advantages over organic fluorophores: high luminescence, far longer stability against photobleaching, and a range of fluorescence wavelengths from blue to infrared, depending on particle size. Thus, we examined the role of MPO and the Ab to MPO in the pathogenesis of glomerulonephritis associated with MPO-ANCA in experimental glomerulonephritis mice using QDs. We demonstrated the QD-conjugated anti-MPO Ab visualized the expression of MPO on the neutrophil surface after stimulation with proinflammatory cytokines. In addition, QD immuno-conjugates with anti-recombinant murine MPO (rmMPO) Ab revealed the trafficking of MPO-ANCA in vivo. Deceleration of blood flow in kidney vessels
occurred in model mice, in which serum proteins including anti-rmMPO Ab were leaked out from collapsed glomeruli into the proximal tubule. Thus, sustained MPO expression on the neutrophil surface was significantly related to glomerulonephritis. These results indicate that the expressed MPO on the activated neutrophils with anti-MPO Ab may coordinately play essential roles in the initial steps for the development of glomerulonephritis.
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