Purified IgG fractions from GBS sera inhibit neurite outgrowth through activation of RhoA and ROCK. A, B, DRG neurons treated with GBS IgG fractions have much shorter neurites (B) compared with control IgG-treated neurons (A). Scale bar, 50 μm. C, Five of seven GBS IgG fractions induce significant (but variable) inhibition of the neurite outgrowth. D, IgG fractions purified from GBS patient (PS1; gray bar) induce significant inhibition of neurite outgrowth in wild-type (WT) DRG neurons but not in the Galgt1-null neurons; control IgG fractions (CS; black bar) do not modulate the growth behavior of wild-type and Galgt1-null neurons. E, IgG fractions from six of seven GBS sera can induce significant but variable activation of RhoA in DRG neurons compared with control IgG. F, Treatment with C3-transferase (RhoA inhibitor) and Y27632 (ROCK inhibitor) significantly reverse the inhibitory effects of GBS IgG fractions (PS1). *p < 0.05.