Complementary contribution of CD4 and CD8 T lymphocytes to T-cell infiltration of the intact and the degenerative spinal cord

The central role of T cells in inflammatory reactions of the central nervous system (CNS) is well documented. However, there is little information about the few T cells found within the noninflamed CNS. In particular, the contribution of CD4(+) and CD8(+) T cells to the lymphocyte pool infiltrating the intact CNS, the location of these cells in CNS white and gray matter, and changes in the cellular composition of T-cell infiltrates coinciding with degeneration are primarily undefined. To address these points, we studied T cells in the intact and degenerative rat spinal cord. in the intact spinal cord, T cells were preferentially located within the gray matter. CD8(+) T cells were more numerous than CD4(+) lymphocytes. In cases of neuroaxonal degeneration or myelin degeneratioa/oligodendrocyte death, T cells were predominantly seen in areas of degeneration and were present in increased numbers. These effects were more pronounced for the CD4(+) than for the CD8(+) T-cell subset. Collectively, these data provide evidence for a clear cellular and compartmental bias in T-cell infiltration of the intact and degenerative spinal cord. This could indicate that CD4(+) and CD8(+) T cells might fulfill complementary roles in the intact and the diseased organ.