Figure 4.

mEPSCs differ in cultured neurons treated with IgG from an individual with no anti-AMPAR reactivity (control IgG), an individual from the original cohort of anti-AMPAR encephalitis with GluA2 bottom lobe ATD reactivity (original patient IgG), and an individual with newly discovered anti-AMPAR antibodies in serum directed against the S1 domain (new patient IgG). (A) Example traces of mEPSCs from neurons treated with IgG from different patients. (B and C) Decreased average peak amplitude of mEPSCs in patient-treated neurons (B) is reflected in a decreased frequency of larger amplitude responses in the cumulative frequency histogram (C). (D) Increased interevent interval in neurons treated with patient material indicates a decrease in event frequency, which is more pronounced with original patient IgG treatment. (E) Incubation of patient IgG with GluA2 fusion proteins specifically depletes anti-AMPAR antibodies (Patient IgG, depleted), while incubation with uninduced bacteria does not (Patient IgG, uninduced; bands in GluA2-ext dom and GluA2-S1 lanes; compare to Fig.3E). Anti-Trx, Thioredoxin loading control. Standard, MagicMark internal exposure standard. (F and G) Patient IgG effect on mEPSC amplitude is dependent on the presence of anti-AMPAR antibodies: preincubation with uninduced bacteria (unind) maintains the patient-specific decrease in mEPSC amplitude (F) and decreased percentage of large events (G), while these effects are lost after AMPAR-specific IgG depletion (depl). n = 6–9 cells, P < 0.0001, one-way ANOVA plus Tukey's post hoc testing.