I型膜增生性肾小球肾炎：内皮细胞和基底膜之间电子致密沉积物

如箭头所示，电镜下左下方的系膜细胞基质插入内皮细胞和基底膜之间，呈现双层基底膜现象。这是I型膜增生性肾小球肾炎。当系膜细胞（有巨噬细胞的功能）随着免疫沉积物来到内皮细胞和基底膜之间时，基底膜呈现这些特征性的改变。在此过程中，它使基底膜结构发生紊乱。
This electron micrograph demonstrates a mesangial cell at the lower left that is interposing its cytoplasm at the arrow into the basement membrane, leading to splitting and reduplication of basement membrane that is piled up above the mesangial cytoplasm in this micrograph. This is MPGN type I. These characteristic EM changes occur when the mesangial cell (which has a macrophage-like function) goes after subendothelial immune deposits, but makes a mess of the basement membrane in the process.