Fig. 5

Diagram displaying cellular activation/infiltration after rat SCI. After the primary insult, there is a much larger secondary injury with extensive infiltration of immune cells. Neutrophil infiltration peaks 24-h post-injury and decreases over the next week. Infiltrating lymphocytes accumulate around blood vessels in gray matter as early as 6 h and T-cell specific lymphocytes peak around 9-day post-injury. Microglia are activated, retracting their cytoplasmic processes and becoming indistinguishable in terms of morphology from the infiltrating PDMs. The astrocytes also become reactive and retract the cytoplasmic processes and migrate to the lesion. Although initially the astrocytes aid in tissue repair, they eventually become scar-forming astrocytes and begin to wall off the ensuing inflammation. The final glial scar is compartmentalized with infiltrating immune cells in the center, microglia interacting with pericytes around the edges, and astrocytes encapsulating the entire tissue containing the inflammatory cells