Background/Purpose: Lupus nephritis affects at least 50% of patients with SLE and is a major cause of morbidity. The pathologic picture of lupus nephritis is complex and the precise mechanisms that underlie the development of lupus nephritis remain unclear.  The present study was undertaken to delineate the differential localization of lymphocytes infiltrating the glomeruli versus the tubulo-interstitium in NZM 2328 mice, a murine model that closely mimics human lupus nephritis.

Methods: Kidneys were evaluated by in situ histology  and immunohistochemistry. Cells infiltrating the glomeruli were separated from those infiltrating the tubulo-interstitium through  enzymatic, magnetic, and mechanical procedures and were characterized by flow cytometry.

Results: B cells and macrophages each represent ~5% of the cells infiltrating both the glomeruli and tubulo-interstitium, whereas CD3⁺ T cells represent 40-60% and 70-80% of the infiltrating cells, respectively. In the tubulo-interstitium, 50-60% of CD3⁺ T cells are CD4⁺, 15-25% are CD8⁺, and 20-30% are DN. In contrast, the T cells infiltrating the glomeruli are only 1-5% CD4⁺ cells and <1% CD8⁺ cells, whereas 95-98% are DN. Furthermore, most of the T cells infiltrating the glomeruli display an activated memory phenotype (CD62L^neg, CD44^high, CD69⁺). About 20-25% of these activated T cells are also CD1d tetramer positive, indicative of an iNKT cell phenotype. A significant difference in the abundance of NK1.1⁺ cells was also observed. Among cells infiltrating the glomeruli, 20-35% are NK1.1⁺ , whereas only 3-10% of the cells infiltrating the tubulo-interstitium are NK1.1⁺ . These data are highly relevant in comparison with the composition of T cells in the spleen of NZM 2328 mice. The activated memory T cell subset serves as a major biological surrogate marker of clinical disease progression.  As determined by gene-array analysis, these activated memory T cells display neither a Th1 nor Th2 profile but rather express a Th17 profile and produce IL-17. Most importantly, these activated memory cells progressively increase in numbers during disease development, not only in the spleen, but  in the kidney as well. However, during migration of these cells from the periphery to the kidney and especially into the glomeruli, they lose their CD4⁺ expression and become mostly DN.

Conclusion: The present study is, to our knowledge, the first direct and detailed analysis of the immune infiltrates in the glomeruli and the tubulo-interstitium in lupus kidneys. The identification of DN T cells bearing an activated memory phenotype as the major cell population in the glomeruli of clinically nephritic mice is likely highly relevant to the pathogenesis of human lupus nephritis. Given that DN T cells are found in kidney biopsies of patients with lupus nephritis and these cells are capable of producing IL-17, our results further support this subset of cells as contributory to development of kidney damage.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/preferential-infiltration-of-double-negative-dn-t-cells-into-the-glomeruli-of-nzm-2328-lupus-mice/