Intravenous immunoglobulin replacement induces an in vivo reduction of inflammatory monocytes and retains the monocyte ability to respond to bacterial stimulation in patients with common variable immunodeficiencies.

Intravenous IgG administration induces significant modifications in the innate and adaptive compartment of the immune system including the monocyte/macrophage system. We analyzed the in vivo effect of IgG administered at replacement dosages on the frequency of monocytes subsets, on the modulation of CD11b and sialic acid-binding immunoglobulin-like lectin receptor (Siglec 9) expression and on monocytes production of reactive oxygen species. We showed that patients with Common Variable Immune Deficiency have an increased frequency pro-inflammatory intermediate CD14(++)CD16(+) monocytes and an increased expression of CD11b and Siglec 9 on monocytes. IgG administered at replacement dosages exerted an in vivo anti-inflammatory effect as shown by a reduction of circulating monocytes, of intermediate pro-inflammatory monocytes, of CD11b and Siglec 9 expression and of ex vivo monocytes oxidative burst. Nevertheless, intravenous IgG administration did not affect the monocyte functional ability to respond to a bacterial stimulation in terms of CD11b and Siglec 9 expression and reactive oxygen species production.