Prophylactic treatment with sulphonated immunoglobulin G attenuates development of mechanical allodynia-like response in mice with neuropathic pain

Human immunoglobulin G (IgG) concentrates are immune-modulating, anti-inflammatory plasma-derived products. Clinical studies in recent years have suggested that IgG attenuates neuropathic pain. In this study, effects of sulphonated IgG on the development and maintenance of a mechanical allodynia-like response were examined in mice with neuropathic pain induced by a partial sciatic nerve ligation (PSL). When sulphonated IgG (400 or 1,000 mg/kg/day, i.p.) was administered for 5 days, from 1 day before surgery to post-operative day (POD) 3, the development of a mechanical allodynia-like response was attenuated. On the other hand, sulphonated IgG had little effect on the maintenance of a mechanical allodynia-like response when administered for 5 days, from POD 11 to POD 15, at which time a mechanical allodynia-like response had already been developed. To explore the mechanism of sulphonated IgG, the mRNA expression of inflammatory cytokines was evaluated in the injured sciatic nerve. Sulphonated IgG (1,000 mg/kg/day, i.p.) that was administered for 3 days, from 1 day before surgery to POD 1, significantly attenuated the up-regulation of tumor necrosis factor-α and monocyte chemotactic protein-1 mRNAs on POD 1. These results suggest that prophylactic treatment with sulphonated IgG attenuates the development of mechanical allodynia-like response by inhibition of inflammatory cytokine expression in mice with PSL.