Background Systemic Lupus Erythematosus (SLE) is a chronic autoimmune disease, the most frequent severe manifestation of which is lupus nephritis (LuN). We have previously shown that tubulointerstitial inflammation (TII) is a usual feature of LuN with TFH cells participating in conjugates with B cells, and driving adaptive immune responses (1).
Objectives To investigate the role of innate immune responses and plasmacytoid dendritic cells (pDCs) in LuN TII
Methods We utilized multichannel immunofluorescent confocal microscopy, performed on 18 human biopsy samples of LuN and compared this to 7 cases of de-identified normal kidney (NK) biopsies. Control staining for Igk and IgE in addition to stains for CD20, BDCA2, IgE, and MxA (a protein, upregulated in IFN-a signature responses) were performed. To check for the presence of serum antibodies, matched human serum from 5 of the biopsies analyzed was assayed by means of ELISA for the presence of anti-dsDNA IgE antibodies.
Results Control staining for Igk and IgE was performed with over 90% overlap between the two stains across NK and LuN samples. Stains for CD20, BDCA2, IgE, and MxA (a protein, upregulated in IFN-a signature responses) were performed and revealed the presence of activated MxA+ pDCs in close association with IgE antibodies and CD20+ cells in LuN but not NK tissue. IgE staining was present in the tubulointersititium in 16 of 18 LuN biopsies as compared to 1 out of 7 NK biopsies. Qualitative analysis indicated that tubulointerstitial staining was more prominent in all LuN cases as compared to the single NK case. Among the LuN biopsies studied, a germinal center was clearly present in one sample with the finding of IgE co-localized with B cells and surrounded by activated pDCs, similar to that seen in tonsil controls, raising the possibility of in situ production of IgE antibodies.
To check for the presence of serum antibodies, matched human serum from 5 of the biopsies analyzed was assayed by means of ELISA for the presence of anti-dsDNA IgE antibodies. 4 out of 5 (80%) of the samples had detectable levels of IgE anti-dsDNA antibody. Matched renal biopsies revealed interstitial staining with IgE in all of the cases.
Conclusions Our data suggests that activated pDCs are present in a majority of LuN TII cases, and are closely associated with IgE antibodies and CD20+ B cells. Furthermore, matched serum experiments showed the presence of detectable anti-dsDNA IgE antibodies in 4 of 5 cases. The finding of a germinal center in complex with IgE staining and activated pDCs raises the possibility of in situ production of IgE mediating LuN TII and participating in the pathogenesis of this disease, providing a link between the innate and adaptive immune responses and revealing a new role for IgE in autoimmunity.
Liarski, Vladimir M., et al. Cell distance mapping identifies functional T follicular helper cells in inflamed human renal tissue. Science translational medicine 6.230 (2014): 230ra46–230ra46.
Acknowledgement Research reported in this publication was supported by the National Center For Advancing Translational Sciences of the National Institutes of Health under Award Number KL2TR000431. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
Disclosure of Interest V. Liarski Grant/research support from: NCFATS KL2 TR000431, J. Henault Employee of: MedImmune, R. Herbst Employee of: MedImmune, R. Kolbeck Employee of: MedImmune, M. Sanjuan Employee of: MedImmune, M. Clark Grant/research support from: NIAMS R01-AR55646–03