Cytokine expression. Cytokine expressions of IL-1β, IL-10, IFN-γ and TNF-α after transection. Statistical analyses were made with one-way ANOVA and t-test. Only those expressions that had t-values > 0 (relative to control expression) were taken into account. Significance values are marked as follows: * p = 0.05; ** p = 0.01; *** p = 0.001. The expression changes of different cytokines mRNAs could be observed at multiple time points after peripheral nerve injury. Expressions in control samples could only be observed in the epi-/perineurium. The proximal stump expressed IL-1β, TNF-α and IL-10 in a cyclic manner. The main time points for the cyclic expression pattern were 1-5, 14-21 and 35 days. The distal stump showed marked expression of these cytokines during days 1-3 after injury, but for cytokine IL-1β also at day 14. IL-10 was markedly expressed at 21 and 35 days after injury. IFN-γ was not expressed in either compartment before day 5. The proximal stump showed marked expression of this cytokine at 14 days after injury and the distal stump at 21 days. IL-4 was not markedly expressed in this study.