The protective effect of modified intravenous immunoglobulin in LPS sepsis model is associated with an increased IRA B cells response

Intravenous immunoglobulin preparations (IVIg) that have undergone a mild oxidizing treatment with ferrous ions have an increased polyspecificity, which is not associated with a higher propensity to form aggregates. Among other biological properties of the modified IVIg, a protective effect in LPS sepsis model stands out as the native preparation is totally devoid of it or even exacerbates sepsis. A recent finding identified an LPS induced subset of B1 lymphocytes that migrate from the peritoneal cavity to the spleen acquiring the expression of CD93, GM-CSF as well as the capacity to control sepsis. This report demonstrates that modified IVIg, but not the native preparation, causes a further increase in this population during LPS sepsis. Partial targeted suppression of the peritoneal B cell proliferation by an intracellular dye abrogates this effect and the clinical benefit of modified IVIg.