IVIg modulates the MAPK pathway. Tonsillar B cells were incubated with anti-IgM–coated beads in the presence or absence of IVIg for 30 seconds or 2 minutes before lysis. Total cell lysates were prepared for WB using anti-phospho ERK1 and anti-phospho ERK2 (A) or anti-phospho p38 and anti-PI3K (B) Abs. Values indicate relative density of the WB bands normalized to that obtained for β-actin. Data are representative of 3 separate experiments.