IgM Immunoglobulin Influences Recovery after Cervical Spinal Cord Injury by Modulating the IgG Autoantibody Response

Spinal cord injury (SCI) results in the development of detrimental autoantibodies against the lesioned spinal cord. IgM immunoglobulin maintains homeostasis against IgG-autoantibody responses, but its effect on SCI recovery remains unknown. In the present study we investigated the role of IgM immunoglobulin in influencing recovery after SCI. To this end, we induced cervical SCI at the C6/C7 level in mice that lacked secreted IgM immunoglobulin [IgM-knock-out (KO)] and their wild-type (WT) littermate controls. Overall, the absence of secretory IgM resulted in worse outcomes as compared with WT mice with SCI. At two weeks after injury, IgM-KO mice had significantly more IgG antibodies, which fixed the complement system, in the injured spinal cord parenchyma. In addition to these findings, IgM-KO mice had more parenchymal T-lymphocytes as well as CD11b+ microglia/macrophages, which co-localized with myelin. At 10 weeks after injury, IgM-KO mice showed significant impairment in neurobehavioral recovery, such as deteriorated coordination, reduced hindlimb swing speed and print area. These neurobehavioral detriments were coupled with increased lesional tissue and myelin loss. Taken together, this study provides the first evidence for the importance of IgM immunoglobulin in modulating recovery after SCI and suggests that modulating IgM could be a novel therapeutic approach to enhance recovery after SCI.

Improving outcomes of severe infections by multidrug-resistant pathogens with polyclonal IgM-enriched immunoglobulins

The emergence of infections by multidrug-resistant (MDR) Gram-negative bacteria, which is accompanied by considerable mortality due to inappropriate therapy, led to the investigation of whether adjunctive treatment with one polyclonal IgM-enriched immunoglobulin preparation (IgGAM) would improve outcomes. One hundred patients in Greece with microbiologically confirmed severe infections by MDR Gram-negative bacteria acquired after admission to the Intensive Care Unit and treated with IgGAM were retrospectively analysed from a large prospective multicentre cohort. A similar number of patient comparators well-matched for stage of sepsis, source of infection, appropriateness of antimicrobials and co-morbidities coming from the same cohort were selected. All-cause 28-day mortality was the primary end point; mortality by extensively drug-resistant (XDR) pathogens and time to breakthrough bacteraemia were the secondary end points. Fifty-eight of the comparators and 39 of the IgGAM-treated cases died by day 28 (p 0.011). The OR for death under IgGAM treatment was 0.46 (95% CI 0.26-0.85). Stepwise regression analysis revealed that IgGAM was associated with favourable outcome whereas acute coagulopathy, cardiovascular failure, chronic obstructive pulmonary disease and chronic renal disease were associated with unfavourable outcome. Thirty-nine of 62 comparators (62.9%) were infected by XDR Gram-negative bacteria and died by day 28 compared with 25 of 65 cases treated with IgGAM (38.5%) (p 0.008). Median times to breakthrough bacteraemia were 4 days and 10 days, respectively (p <0.0001). Results favour the use of IgGAM as an adjunct to antimicrobial treatment for the management of septic shock caused by MDR Gram-negative bacteria. A prospective randomized trial is warranted.