Background Renal impairment is the leading cause of morbidity and mortality in systemic lupus erythematosus. Tertiary lymphoid organs (TLO) are organized lymphoid structures that develop in response to inflammatory signals from tissues. They may organize into a functional ectopic germinal center. Their pathogenic role in the evolution of kidney function in lupus nephritis remains uncertain.
Method To assess the correlation between tertiary lymphoid organs and B-cell infiltrates and the severity and outcome of kidney function, we conducted a retrospective study of renal biopsy in patients with lupus nephritis. Immunophenotyping of the cell infiltrate was evaluated by immunohistochemistry. We assessed the B-cell infiltrate with a semi-quantitative score.
Results 18 adult patient biopsies identified over the 10-year period met the inclusion criteria.
Immunophenotyping of the inflammatory infiltrate was performed in 17 patients. There was no inflammatory infiltrate in 3 patients. Scattered T and B cells were found in 4 patients and 40% of patients showed organized clusters of T and B lymphocytes (grade 3 and 4 infiltration) with TLO in 2 biopsies. 9 of the 18 patients went into complete renal remission. Of the 12 patients with unorganized inflammatory infiltrates (grade 0, 1, 2), 7 patients (58.3%) achieved recovery. In contrast, 2 out of 5 patients (40%) with organized infiltrates (3 and 4) reached complete renal remission (p=0.44). The time to renal remission was longer in patient with unorganized infiltration than those with organized infiltrate (median time over 24 vs. 18.9 months respectively, p=0.24) (figure 1). Of the 9 patients with renal remission, 4 relapsed. Finally, 4 patients required dialysis, including 1 death.
Conclusion The presence of intrarenal B cells rarely forms TLO in lupus nephritis. Due to the small sample size, we were unable to determine their prognostic role. Nevertheless, we report here the longer time to renal remission for grade 3 and 4 infiltrates; prospective studies with repeated renal biopsies are needed to better characterize their relationship to disease progression.
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