Characterization of early and terminal complement proteins associated with polymorphonuclear leukocytes in vitro and in vivo after spinal cord injury

The complement system can affect the central nervous system (CNS) by regulating physiological events. After a traumatic CNS injury, complement activation can lead to the formation of C5b-9 membrane attack complex (C5b-9/MAC), potentially lysing cells. Infiltrating immune cells, specifically polymorphonuclear leukocytes (PMNs), might serve as a local source of complement post-injury. PMNs are among the first immune cells to reach the CNS after injury. This study characterizes the early and terminal complement proteins associated with PMNs both in vitro and in vivo following spinal cord injury (SCI), suggesting PMNs play a role in complement delivery and activation in the post-SCI environment.

• 1
  Stimulated or unstimulated PMNs expressed mRNAs encoding for C1q, C3, and C4, but not C5, C6, C7 or C9 in culture. Complement protein C1q or C3 was also detected in less than 30% of cultured PMNs.
• 2
  Over 70% of PMNs infiltrating the injured spinal cord were associated with C1q, C3, C7, and C5b-9/MAC three days post-SCI, with C7 and C5b-9/MAC localized to granular vesicles within PMNs at the spinal cord epicenter.
• 3
  PMNs were observed in the injured spinal cord for weeks post-SCI, suggesting a chronic influence on complement-mediated events and SCI pathogenesis after trauma.