Infiltrating PMNs in the injured spinal cord are associated with the early and terminal complement proteins 3 days post-SCI. Cells isolated from spinal cord (T8-T10) of control (A) or injured rats (B & C) were labeled with a FITC-conjugated anti-PMN antibody and a Cy5-conjugated antibody for C1q, C3, C7 or C5b-9, or appropriate IgG controls before analyzed on a FACS Calibur flow cytometer. After 3 days following SCI (B), the number of cells positive for C1q, C3, C7, or C5b-9 was elevated compared to that from control (A). However, only some of the complement-positive cells were PMNs (C & E) and that most PMNs that infiltrated the injured spinal cord were also positive for C1q, C3, C7, and C5b-9 (C & D). All flow cytometric gates were set using control IgG isotype labeled cells. # = significantly (P < 0.05) different from uninjured control (Con). n = 5. Number of experiment replication = 2.