Participation of macrophages in segmental endocapillary proliferation preceding focal glomerular sclerosis

We studied infiltrating cells in the glomeruli of eight cases with focal segmental endocapillary proliferation (FSEP) using monoclonal antibodies to leukocyte common antigen, T cells, B cells, and monocytes/macrophages (Mo/Mφ). It was demonstrated by sequential biopsies performed in five cases that FSEP preceded focal glomerular sclerosis (FGS). Cell types in FSEP were compared with those in FGS from 17 patients with persistent nephrotic syndrome, ten non‐nephrotic patients, and eight patients with nephrotic syndrome which was initially responsive to steroid therapy but relapsed, as well as minimal change specimens from nine nephrotic patients. In the glomeruli, the mean total leukocyte counts increased significantly in the FSEP group (P < 0.01). The serial sections in FSEP revealed that Mo/Mφ were the predominant cells and were localized in areas of endocapillary proliferation. T‐cell or B‐cell infiltration was less marked. The extensive intracapillary distribution of p150,95 antigen belonging to the integrin family and acting as a C3bi receptor suggested that FSEP may be mediated by adhesion molecules expressed on Mo/Mφ. These findings indicate that Mo/Mφ may play a key role in FGS which shows endocapillary proliferation in the initial stage.