Previously, we have shown that spinal cord CD4+ T lymphocytes contribute to L5Tx-induced maintenance of mechanical hypersensitivity [4]. To identify the phenotype of CD4+ T lymphocytes involved in the development of L5Tx-induced mechanical hypersensitivity, we examined CD4+ T lymphocytes in both peripheral lymphoid tissues and the lumbar spinal cord via flow cytometry with antibodies that identify the Th1 and Th2 subtypes. WT BALB/c mice were randomly assigned to naive (no surgery), L5Tx, and sham groups. Since 7 days post-surgery is the peak time of detecting spinal cord-infiltrating CD4+ T lymphocytes, samples were collected at day 7 post-surgery.