IgE-mediated immune response and antibody-mediated rejection

Background and objectives Active antibody-mediated rejection is the main cause of kidney transplant loss, sharing with SLE the alloimmune response and the systemic activation of the IFN-a pathway. IgE-mediated immune response plays a key role in the development of SLE nephritis and is associated with IFN-a secretion. The aim of our study was to investigate IgE-mediated immune response in antibody-mediated rejection. Design, setting, participants, & measurements This was a cross-sectional study of 56 biopsy-proven antibodymediated rejection study participants, 80 recipients with normal graft function/histology (control), 16 study participants with interstitial fibrosis/tubular atrophy, and six participants with SLE. We evaluated graft IgE deposition, tryptase (a mast cell marker), and CD203 (a specific marker of activated basophils) by immunofluorescence/confocal microscopy. In addition, we measured serum concentration of human myxovirus resistance protein 1, an IFN-a–induced protein, and anti-HLA IgE. Results We observed a significantly higher IgE deposition in tubules and glomeruli in antibody-mediated rejection (1766679 pixels) and SLE (1495643 pixels) compared with interstitial fibrosis/tubular atrophy (5826122 pixels) and control (253650 pixels). Patients with antibody-mediated rejection, but not control patients and patients with interstitial fibrosis/tubular atrophy, presented circulating anti-HLA IgE antibodies, although with a low mean fluorescence intensity. In addition, immunofluorescence revealed the presence of both mast cells and activated basophils in antibody-mediated rejection but not in control and interstitial fibrosis/tubular atrophy. The concentration of circulating basophils was significantly higher in antibody-mediated rejection compared with control and interstitial fibrosis/tubular atrophy. MxA serum levels were significantly higher in antibodymediated rejection compared with control and correlated with the extent of IgE deposition. Conclusions Our data suggest that IgE deposition and the subsequent recruitment of basophils and mast cells within the kidney transplant might play a role in antibody-mediated rejection.