Electron microscopy of macrophages in PBS controls.

(A) Low power electron micrograph of the optic nerve periphery at 1 w after injury, with a pale yellow overlay indicating the nerve and pale red overlay indicating numerous macrophages within it. (B) Peripheral macrophages containing a variety of multilamellar and multivesicular bodies, products of phagocytic activity. (C) Macrophage with an irregular nucleus (n) and large debris-filled multilamellar bodies. (D) Centrally located macrophages containing large vacuoles with apparent remnants of degenerating axons. (E) Central, smaller (possibly microglia) cell with multilamellar and multivesicular bodies. (F) Peripheral macrophages at 2 weeks, located within the glia limitans (gl). Some vacuoles with axonal debris are present but the cytoplasm also contains lipid inclusions (asterisks) and dark granules (g). Inset: high magnification view of putative lipid inclusions, showing lack of a bounding membrane. (G) Large central macrophage with a bilobed nucleus (n) at 2 weeks, containing a mixture of vacuoles with axonal debris, and lipid inclusions (asterisks). Scale bar: 20 μm in A; 5 μm in B, D; 2 μm in C, E, F, G; 0.5 μm in inset.