Figure 1. CRPS patient serum and IgM had pronociceptive effects in B cell deficient fracture mice.

At 3 weeks after tibia fracture and casting (FX) muMT mice lacking B cells and IgM exhibited unilateral hindpaw von Frey allodynia (A) and unweighting (B). After intraperitoneal injection of early (1–12 months post injury) CRPS patient serum (0.5ml, I.P) or IgM (500ug/1ml, I.P.) into 3 weeks post FX muMT mice, the mice gradually developed increased allodynia and unweighting over the ensuing week, and consistent with the 6 day half-life of IgM, these pronociceptive effects resolved by 2 weeks post-injection. The pronociceptive effects of the CRPS serum were restricted to the FX limb and there was no serum effect on post FX hindpaw edema or warmth (data not shown). No pronociceptive effects were observed after intraperitoneal injection of early CRPS patient IgG (5mg/1ml, I.P.) or after injection of control subject serum (0.5ml, I.P.) in 3 weeks post-FX mice. Measurements for (A) represent the difference between the FX side and contralateral paw, thus a negative value represents a decrease in mechanical withdrawal thresholds on the affected side. Measurements for (B) represent weight-bearing on the FX hind limb as a ratio to half of the total bilateral hind limb loading, thus, a percentage lower than 100% represents hindpaw unweighting. A 2-way repeated measures analysis of variance was used to test the effects of each treatment group on the dependent variables over time, using a Sidak correction test for post hoc contrasts. Data are expressed as mean values ± SEM, n = 5 patients per cohort and each patients serum or immunoglobulin was injected into 3 mice for a total n of 15 mice. #P < 0.05, ## P < 0.01, and ### P < 0.001 for each injection cohort vs the control serum treatment group. MuMT: mice lacking B cells, FX: fracture, BL: baseline, 3wkFX: 3 weeks after fracture