The macrophage in acute neural injury: Changes in cell numbers over time and levels of cytokine production in mammalian central and peripheral nervous systems

We evaluated the timing and density of ED-1-positive macrophage accumulatio n (ED 1 is the primary antibody for the macrophage) and measured cytokine p roduction by macrophages in standardized compression injuries to the spinal cord and sciatic nerves of individual rats 3, 5, 10 and 21 days post-injur y. The actual site of mechanical damage to the nervous tissue, and a more d istant site where Wallerian degeneration had occurred, were evaluated in bo th the peripheral nervous system (PNS) and the central nervous system (CNS) at these time points. The initial accumulation of activated macrophages wa s similar at both the central and peripheral sites of damage. Subsequently, macrophage densities at all locations studied were statistically significa ntly higher in the spinal cord than in the sciatic nerve at every time poin t but one. The peak concentrations of three cytokines, tumor necrosis facto r alpha (TNF alpha), interleukin-1 (IL-1) and interleukin-6 (IL-6), appeare d earlier and were statistically significantly higher in injured spinal cor d than in injured sciatic nerve. We discuss the meaning of these data relat ive to the known differences in the reparative responses of the PNS and CNS to injury.