Fig. 2.

NMDAR-Ab from different origins target do not compete for target binding. a Experimental design of the in vitro immuno-competition test. Hippocampal cultures (12 div) were first incubated with PSY + NMDAR-Ab (IgG1) labeled in green. Cells were then incubated with a second Healthy + , PSY + or Enceph + IgG (IgG2) labeled in red. Three out of three Healthy + , four out of nine PSY + , and one out of seven encephalitis purified IgG samples were used and pooled for comparisons. b Representative dendritic areas labeled with PSY + NMDAR-Ab (IgG1, 5 µg ml⁻¹, green) and treated with the same IgG (IgG2 = ident. PSY + , 5 µg ml⁻¹, red). Scale bar, 2 µm. Right panel: histogram of IgG2 fluorescence intensity within IgG1 area. The use of the same IgG (IgG2 = ident. PSY + ) results in a distribution fitted with a single Gaussian. Insets, staining from a single cluster. Scale bar, 500 nm. c Representative dendritic areas labeled with a PSY + NMDAR-Ab (IgG1, 5 µg ml⁻¹, green) and treated with NMDAR-Ab from another PSY + patient (IgG2 = Diff. PSY + ), a healthy individual (IgG2 = Healthy + ) or a patient with anti-NMDAR encephalitis (IgG2 = Enceph + ). Scale bar, 2 µm. Bottom panels: Corresponding histograms of IgG2 fluorescence intensity within IgG1 area for the different competing conditions. Insets, staining from single clusters. Scale bar, 500 nm. d Cumulative distributions of IgG2 intensity within IgG1 cluster areas according to the different competing conditions: PSY + /Ident. PSY + (n = 38 dendritic regions, N = 10 neurons), PSY + /Diff. PSY + (n = 99, N = 32), PSY + /Healthy + (n = 78, N = 26) or PSY + /Enceph + (n = 51, N = 15); *P < 0.05, **P < 0.005, Kolmogorov–Smirnov test. e Competing biotinylation assay in rat hippocampal slices. Pre-incubation of rat brain sections with serum from a patient with anti-NMDAR encephalitis blocks the reactivity of biotinylated IgG from another patient with anti-NMDAR encephalitis (left and middle panels). Pre-incubated with serum from a healthy control does not block the reactivity of biotinylated IgG from a patient with anti-NMDAR encephalitis (e2 and e4). Pre-incubation of sections of rat brain with serum of five patients with schizophrenia does not block the reactivity of biotinylated IgG from a patient with anti-NMDAR encephalitis (e5 and e6)