Immunomodulation of human B cells following treatment with intravenous immunoglobulins involves increased phosphorylation of extracellular signal-regulated kinases 1 and 2

Abstract

In the treatment of autoimmune diseases, intravenous Igs (IVIg) are assumed to modulate immune cells through the binding of surface receptors. IVIg act upon definite human B cell populations to modulate Ig repertoire, and such modulation might proceed through intracellular signaling. However, the heterogeneity of human B cell populations complicates investigations of the intracellular pathways involved in IVIg-induced B cell modulation. The aim of this study was to establish a model allowing the screening of IVIg signal transduction in human B cell lines and to attempt transposing observations made in cell lines to normal human B lymphocytes. Nine human B cell lines were treated with IVIg with the goal of selecting the most suitable model for human B lymphocytes. The IgG(+) DB cell line, whose response was similar to that of human B lymphocytes, showed reduced IVIg modulation following addition of PD98059, an inhibitor of extracellular signal-regulated protein kinase 1/2 (ERK1/2). The IVIg-induced ERK1/2 phosphorylation was indeed proportional to the dosage of monomeric IVIg used when tested on DB cells as well as Pfeiffer cells, another IgG(+) cell line. In addition, two other intermediates, Grb2-associated binder 1 (Gab1) and Akt, showed increased phosphorylation in IVIg-treated DB cells. IVIg induction of ERK1/2 phosphorylation was finally observed in peripheral human B lymphocytes, specifically within the IgG(+) B cell population. In conclusion, IVIg immunomodulation of human B cells can thus be linked to intracellular transduction pathways involving the phosphorylation of ERK1/2, which in combination with Gab1 and Akt, may be related to B cell antigen receptor signaling.