Figure 4. Increased percentages of plasma cells and autoantibody production contribute to autoimmune dysfunction in C9orf72^−/− mice.

(A) FACS analysis reveals a population of cells transitioning from mature B cells to plasma cells indicated by a decrease in expression of mature B cell markers, CD19 and B220 (blue box), and concomitant strong expression of the mature plasma cell marker CD138. Gating strategy from WT and C9orf72^−/− 18 week male spleen is represented to show a transitioning plasma cell population that is prominent in C9orf72^−/− compared with WT. (B) Gating strategy for a mature plasma cell population (B220⁻CD19⁻CD45^Int/HiCD138⁺) in 18 week male spleen demonstrates increased mature plasma cells in C9orf72^−/−compared with WT. (C) Graphical representation of increased transitioning and (D) mature plasma cell populations by FACS analysis shows significantly increased percentages in C9orf72^−/−spleen and LN in comparison to WT at 18 weeks of age and older. (E,F) Serum ELISA assays indicate significant increases in IgG and IgM type RF autoantibodies, consistent with the observed systemic autoimmune response in null mice. C9orf72^+/− mice display values comparable to WT, consistent with absence of any observed phenotype. (C,D) Graphs represent mean ± s.e.m. (*P ≤ 0.05, **P ≤ 0.01 and ***P ≤ 0.001 by unpaired Students t-test), n = 4 females per genotype (E,F) Graphs represent mean ± s.e.m. (*P ≤ 0.05, **P ≤ 0.01 and ***P ≤ 0.001 by one-way ANOVA), n ≥ 22 per genotype, 9–65 week old males and 8–42 week old females.