Lumbar radicular pain after intervertebral disc herniation may be associated with mechanical compression of the nerve roots, but also release of pro-inflammatory cytokines from nucleus pulposus (NP) tissue. In an animal model mimicking the clinical situation after disc herniation, we examined the pro-inflammatory and pro-nociceptive effect of NP tissue exposed to the dorsal nerve roots. Using quantitative polymerase chain reaction (qPCR), an up-regulation of interferon (IFN)-γ, IFN-α2, IFN-1β and IFN-α4 in NP tissue exposed to the spinal dorsal nerve roots for one hour was demonstrated. Moreover, the data indicated a significant up-regulation of cluster of differentiation 68 (CD68), corresponding to an increase in lysosomal activity and macrophage activation. A correlation between IFN-γ, known to activate macrophages, and CD68 was also observed. However, F4/80, a marker specific for blood-borne macrophages, was not detected. This suggests that tissue-specific macrophages within NP are activated after disc herniation. As in previous studies, single cell recordings of the dorsal horn neurons showed significant increase in the C-fibre response when NP was applied onto the spinal dorsal nerve roots. Moreover, IFN-γ had a similar effect as NP tissue, with a clear increase in C-fibre response, suggesting that IFN-γ released from the herniated disc may have an important pro-nociceptive and pro-inflammatory effect. To follow up the findings from the animal study three IFN-γ single nucleotide polymorphisms (SNPs) (rs2069705, rs2069718 and rs1861494) were studied in patients with acute lumbar radicular pain due to disc herniation. The data showed a clear trend regarding pain intensity measured with visual analogue scale (VAS), and significant differences regarding function and disability, measured with oswestry disability index (ODI). This suggests that the SNPs may be involved in determining the transcription rate of IFN-γ. In summary, our data show that tissue-specific, not circulating, macrophages are important in the patophysiological response following disc herniation. Further, the results indicate that IFN-γ may be important for the increased excitability of dorsal horn neurons induced by NP. The present study suggests that IFN-γ has an important role in acute lumbar radicular pain due to disc herniation.