The Pattern of Interleukin-12 and T-Helper Types 1 and 2 Cytokine Expression in Herniated Lumbar Disc Tissue

STUDY DESIGN: A study was conducted to investigate the expression of cytokines related to the immune reaction in herniated lumbar disc tissues. OBJECTIVE: To investigate the immunologic status of lumbar disc tissue and the type of immune reaction that occurs in response to lumbar disc herniation. SUMMARY OF BACKGROUND DATA: It has been proposed that herniated lumbar disc tissue causes an immune reaction. Various inflammatory cells, proinflammatory cytokines, antibodies, and immunoglobulins have been identified in and around herniated lumbar disc tissue. Recently, it has been reported that lumbar disc tissue may be another potential immune-privileged site in the human body. METHODS: This study included 40 herniated lumbar disc tissues: 20 contained and 20 noncontained discs. The concentrations of interleukin-12, T-helper Type 1, interferon-gamma (IFN-gamma), and Th2 (IL-4) cytokines were determined by enzyme-linked immunosorbent assay, respectively. The results were compared between the two groups. RESULTS: The concentrations of interleukin-12 and interferon-gamma were higher in the noncontained discs than in the contained discs: 28.3 +/- 10.7 pg/mL vs 9.2 +/- 4.2 pg/mL (P = 0.001) and 4.7 +/- 5.0 pg/mL vs 2.3 +/- 3.8 pg/mL (P = 0.029), respectively. On the contrary, the concentration of IL-4 was higher in the contained discs than in the noncontained discs: 24.3 +/- 20.1 pg/mL vs 1.9 +/- 4.5 pg/mL; P= 0.001. The degrees of interleukin-12 and interferon-gamma expression were negatively correlated with that of IL-4 (n = 40): correlation coefficient, -0.671 (P = 0.001) and correlation coefficient, -0.344 (P = 0.03), respectively. CONCLUSIONS: The findings suggest that preferential expression of Th2 cytokines by disc cells, as shown in contained discs, is another factor contributing to the immune privileged status of lumbar disc tissue. The exposure of lumbar disc tissue to the epidural space may increase the concentration of interleukin-12 in herniated lumbar disc tissue, changing the pattern of T-helper Types 1 and 2 cytokine expression.