Figure 4  Detection of CD154+CD4+ T lymphocytes in the lumbar spinal cord and the mechanical sensitivity of CD154 KO mice post-L5Tx. In A, lumbar spinal cord sections from WT BALB/c mice 7 days post-L5Tx were processed for immunohistochemical analysis of CD4 (in green), CD40L (CD154, TRITC in red), and nuclei (DAPI in blue). CD154+CD4+ T lymphocytes (dual-labeled with CD4 and CD154, in yellow when merged) were detected within the parenchyma of the dorsal horn region in the spinal cord 7 days post-L5Tx. Examples of two detected cells (from ipsilateral side) are shown here. Merged images are shown on the far right (40×, Scale bar = 10 µm). In B, WT BALB/c mice and BALB/c CD154 KO mice were subjected to either L5Tx or sham surgery. All mice were tested for their mechanical sensitivity with von Frey filaments using the Up-Down method as described in the Methods. Data are presented as mean ± SEM (n = 8). *w indicates p < 0.05 between the indicated group and the corresponding day 0 group within the WT mice. *k indicates p < 0.05 between the indicated group and the corresponding day 0 group within the CD154 KO mice.