Changes in plasma cytokines associated with peripheral nerve injury

Plasma levels of interleukins 1, 2, 4 and 6 and tumor necrosis factor (TNF) were measured from 0 to 30 days in rats after a unilateral crush of the sciatic nerve at the level of the sciatic notch and after sham operations without nerve crush. Interleukin-6 was observed to peak and return to baseline levels within 24 h and remained at baseline for the duration of the experiment. An initial sharp rise in interleukin-1 and TNF was observed in all animals 1-2 days after the operation. A transient increase in interleukin-1 and TNF was also observed only in nerve-injured animals between 10 and 14 days after injury. A large increase in interleukin-2 appeared only in nerve-injured animals beginning at 11 days after injury and remained elevated for the remaining study period. No alterations in plasma interleukin-4 were observed at any time point. The experiments provide preliminary evidence for significant trauma-induced alterations in plasma cytokines which could provide a basis for some of the diffuse responses of peripheral neurons to trauma. The biphasic nature changes in plasma cytokines suggest that the immune system may participate in tissue reactions involved in the recovery from nerve injury.