Fig. 6.

WT-5xfAD mice exhibit increased total brain IgG but no Aβ-specific antibodies or Aβ-reactive B/T cells. (A) ELISA of soluble brain lysates confirms that WT-5xfAD mice exhibit significantly more brain IgG (∼150%) compared with WT-WT mice. Unsurprisingly, no levels of IgG are observed in Rag-WT or Rag-5xfAD mice. (B) Despite the increase in brain IgG, no differences are observed between levels of peripheral IgG in plasma detected using the same ELISA. (C–F) Several assays demonstrate a lack of specific Aβ-reactive cells or anti-Aβ antibodies in WT-5xfAD compared with WT-WT. (C) ELISpot assay of splenocytes demonstrates background levels of Aβ-binding B cells within the spleen of WT-WT and WT-5xfAD mice; n = 5 animals/group. However, positive control mice receiving an active Aβ immunogen exhibit a very strong anti-Aβ B-cell response. (D and F) Analysis of lymphocytes isolated from the cervical lymph nodes (pooled deep and superficial) again find no difference in number of reactive cells between WT-WT and WT-5xfAD mice and that overall numbers of reactive cells are less than observed in splenocytes samples; n = 10 animals/group. (E) ELISA of sera collected from WT-WT, WT-5xfAD, and Rag-5xfAD mice demonstrates that equivalent background levels of Aβ-binding antibodies are detected in both WT-WT and WT-5xfAD mice, well below levels detected in mice receiving active Aβ immunization. (G–J) High-magnification confocal images further demonstrate a lack of IgG labeling of Aβ plaques, whereas surrounding Iba1+ microglial processes colabel with IgG. All data are represented as mean ± SEM. ANOVA, P < 0.05, and Fisher’s PLSD post hoc, ^#P < 0.001.