Figure 3. Engrafted cells in the spinal cord lesions of parabionts are chiefly young-partner derived macrophages.

(A) Parabiotic pairings in which cells of the young partner were transgenically labelled by GFP expression were established. In the old partner lesion from each GFP^young/WT^old pairing, GFP⁺ cells were confined to the lesion (B). (C) No GFP⁺ cells in old partner lesions were found to co-localize with Olig2⁺ nuclei. (D) Almost all GFP⁺ cells co-localized with the macrophage marker MAC1. (E) Characterization of the GFP⁺ inflammatory infiltrate at 5dpl in isochronic-young (iy) (n=3), isochronic-old (io) (n=2) and heterochronic-old (ho) animals (n=4). No statistically significant differences were found amongst the parabotic groups. The overwhelming majority of GFP⁺ cells were MAC1⁺ macrophages. Very few CD4⁺ T cells, CD8⁺ T cells, CD94⁺ natural killer cells, B220⁺ B cells and NIMP-R14⁺ neutrophils were present in the lesions. Data are means ± SEM. Scale bars: B 100 μm, C,D 20 μm.