A prospective study was conducted in patients who underwent surgeries for sciatica. The results were compared to those of control subjects. This study expanded knowledge about the pathogenesis of back pain and sciatica in disc herniation. Nucleus pulposus, retrieved from 10 patients who underwent surgeries for sciatica caused by disc herniation and from 8 patients used as control subjects, was homogenized and together with serum and cerebrospinal fluid was examined for local production of IgG and IgM by rate nephelometry. Experimental data have shown an inflammatory reaction in the nucleus pulposus of animal models. An increased ratio IgGNP/IgGs x 10(3) and IgMNP/IgMs x 10(3) was found in all patient samples, whereas only the IgMNP/IgMs x 10(3) ratio was significantly higher (P < 0.005) when compared with those of the control values. These findings may be secondary to an inflammatory reaction close to the nerve root and prolapsed nucleus pulposus. Therefore, they may contribute in some way to the inflammatory origin of sciatica.