In 2 reports using the CRPS tibia fracture and casting model, IgM but not IgG protein was elevated in injured hind paw skin and sciatic nerve.61,98 Moreover, the authors found transfer of IgM, but not IgG, from either wild-type CRPS mice or patients with CRPS was pronociceptive to B-cell–lacking μMT mice,61,62 which differs from other reports on the pronociceptive role of CRPS IgG transfer.67 This contradiction may be due to the use of wild type vs B-cell–deficient μMT mice, as well as large differences in doses and duration of IgG transfer. The gene discussed is CD40LG; the disease is complex regional pain syndrome.