Brain injuries (BI) induce a state of systemic immunosuppression, leading to a high risk of pneumonia. In this pilot study, we investigated the status of B cell compartment in BI patients.Methods:
A prospective observational study was performed in 2 intensive care units in a university hospital. Blood samples were collected in 14 patients at day 1 and day 7 after acute BI. The phenotype and the ability of B cells to secrete IL-10 were compared to 11 healthy volunteers (HV).Results:
Among the circulating lymphocytes, the frequency of B cells was significantly higher in BI patients compared to HV (p < 0.001). B cells from BI patients displayed an activated profil on day 7 after BI, reflected by a significantly higher proportion of CD27+ memory (p = 0.01) and CD27+ IgD− switched memory B cells (p = 0.02), as well as a significantly higher blood level of IgA (p = 0.001) and IgM (p < 0.001) as compared to day 1. The frequency of IL-10 secreting B cells (IL-10+ B cells) on day 1 and day 7 was significantly lower in BI patients compared to HV (p < 0.05). Interestingly, we observed that all BI patients with high frequency of IL-10+ B cells on day 1 displayed an episode of pneumonia, and had a longer duration of mechanical ventilation and ICU stay compared to BI patients with low proportion of IL-10+ B cells.Conclusion:
This study provides an extensive description of the phenotype and function of B cells in BI patients. Our results suggest that IL-10+ B cells could play a major role in immunosuppression after BI.