Background/Purpose:

The formation of tertiary lymphoid structures (TLS) are known to occur during the development of several diseases, including systemic lupus erythematosus (SLE), but in why and how they are formed is largely unknown and thus under intense investigation. We have recently discovered immune aggregates within the kidney of lupus prone mice resembling TLS. By using gene and protein expression analysis in combination with cell specific analysis and in vivo imaging, we wanted to investigate the formation of TLS in a longitudinal study of murine lupus nephritis.

Methods:

By using immunohistochemistry and immunofluorescent analysis on kidney section from 85 (NZBXNZW)F1 (NZB/W) lupus prone mice and 20 BALB/c control mice the presence of infiltrating immune cells and the formation of highly organized TLS were analyzed. RNA was isolated from: total kidneys; macro dissected TLS from kidneys; and renal lymph nodes (LN) of NZB/W mice at three different disease stages; young (n=5, only total kidney and LN), proven anti-dsDNA ab positive for 4-5 weeks (n=5), and proteinuric (n=5). RNA samples were prepared for sequencing using the Qiagen Allprep total RNA kit (total kidney) or by Trizol extraction (TLS and LN). Sequencing of total kidney mRNA was performed using the Illumina HiSeq 2500. mRNA from TLS and LN was sequenced using the IonTorrent PGM. Differential expression analysis were performed using the edgeR package. To detect the formation of TLS in vivo we performed a pilot study using positron emission tomography (PET) by tail vein injection of the positron-emitting isotope 18-F-fluro-2-deoxy-D-glucose (FDG) combined with computed tomography (CT) for anatomical localization.

Results:

T cells and NK cells were the first cells to infiltrate the kidneys and the detection observed as early as 10 weeks old and before the mice start to produce anti-dsDNA abs.  Gene expression profiling of total kidneys demonstrated an increase in genes involved in T cell activation, NK cell mediated cytotoxicity, B cell activation and inflammation mediated by chemokines and cytokines among others.  Upregulation of genes specific for LN indicating a functional TLS within the kidneys of lupus prone mice. Comparing the gene expression profile in TLS and LN from anti-dsDNA ab positive mice confirmed this, but demonstrated a slightly different gene expression in TLS compared to LN from the same mice. In vivo imaging of renal uptake of FDG revealed a promising retention of FDG in kidneys of young NZB/W mice with anti-dsDNA ab production compared to ab negative NZB/W mice and control BALB/c mice. The FDG uptake increased further in NZB/W mice with detectable TLS and in proteinuric mice.

Conclusion:

The induction of anti-dsDNA antibodies, formation and deposition of immune complexes, and the formation and expansion of TLS in lupus nephritis, may promote progression into an end stage kidney disease in SLE. Understanding the mechanisms of the disease pathology is important for the development of new diagnostic approaches and treatment strategies. In vivo imaging detecting TLS can be useful for early diagnosis and individualized treatment of SLE patients with lupus nephritis.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/functional-tertiary-lymphoid-structures-within-the-kidneys-of-lupus-prone-mice-resembles-lymph-nodes-in-gene-expression-profiling-analysis-and-are-detected-by-in-vivo-imaging/