Distribution of PDGFR alpha, CD11b, and PDGFR beta immunoreactive cells in injured spinal cord white matter. Panels A-D show the distribution of PDGFR alpha positive OPCs (green) at 1 (A, B) and 6 (C, D) weeks after demyelination insult. Panels E-H present CD11b immunoreactive myeloid cells (green) at 1 (E, F) and 6 weeks (G, H) post-injury, while panels I-L show PDGFR beta positive cells (green) at 1 (I, J) and 6 weeks (K, L) post-injury. The first and third columns show sections from wild type mice at 1 and 6 weeks, respectively, after demyelination insult. The second and fourth columns show sections from NG2 null mice at 1 and 6 weeks, respectively, after demyelination insult. Blue: DAPI. Scale bar = 100 μm.