IgG crosses the blood spinal cord barrier and associates with astrocytes. (A) Representative fluorescence images showing the presence of IgG in the spinal cords of an injured rat (left) and a non-injured rat (right). (B) Vessels were stained with RECA-1 (green) and IgG was labeled with a human specific IgG secondary antibody (red). Confocal images demonstrate IgG was able to cross the blood-spinal cord barrier in injured animals (left panel) but not in non-injured animals (right panel). (C) Representative confocal images of microglia/macrophages (Iba-1; green) and IgG (red). IgG was observed in the parenchyma surrounding cells marked by Iba-1 and DAPI (blue). Although IgG was in the vicinity of Iba-1 positive cells, co-localization between IgG and Iba-1 was not observed. (D) Representative confocal images of astrocytes (GFAP; green) and IgG (red). IgG was observed in the parenchyma surrounding and in the cell soma of GFAP positive astrocytes. The co-localization of IgG and astrocytes suggests potential interaction between IgG and astrocytes. Note that an IgG-positive signal was not observed in the spinal cord of rats injected with saline. Confocal images (B-D) were taken from the boxed area, and scale bars represent 50 μm in length.