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Systemic lupus erythematosus (SLE) is a highly heterogeneous autoimmune multisystem disease. LN (Lupus nephritis), a manifestation that occurs in up to 60% of patients with systemic lupus erythematosus, is associated with increased mortality and morbidity. Patients with active LN (class III/IV) have higher mortality and morbidity rates than those with other classes, and they receive more aggressive immunosuppressants. In class III and IV LN, subendothelial immune deposits elicit influx of inflammatory cells, one of the most important one is monocytes and lead to multiple lesions, the most pivotal one is “endocapillary hypercellularity”. Endocapillary hypercellularity in a single glomerulus is enough to classify the biopsy as class III, which emphasizes the importance of recognizing this lesion. Cluster of differentiation (CD) 68 is a highly glycosylated lysosomal transmembrane protein normally expressed by macrophage. We investigated whether the presence of glomerular CD68 positive (+) cells could serve as a surrogate marker for endocapillary hypercellularity in LN.
A total of 90 paraffin embedded renal biopsies of patients with LN were collected and studied immunohistochemically for CD68. All biopsies were scored for the maximum number of glomerular CD68+ cells. A new activity index was calculated in which CD68+ cells replaced endocapillary hypercellularity.
The number of glomerular CD68+ cells was significantly correlated with endocapillary hypercellularity. A cutoff value of 11 for the maximum number of CD68+ cells within 1 glomerulus in a biopsy yielded a sensitivity of 84% and a specificity of 80% for the presence of endocapillary hypercellularity.
In LN, Glomerular CD68+ cells can be used as a marker for endocapillary hypercellularity.