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. 2018 Mar 9;7:e35074. doi: 10.7554/eLife.35074

Figure 6. Cell-intrinsic IgM expression is required for unswitched plasma cell expansion in Lyn−/− mice.

(A) Representative blot and quantification of Ets1 and GAPDH protein in purified splenic B cells from WT, Lyn−/−, and IgM−/− Lyn−/− mice. (B) Composition of the CD138+ plasma cell compartments in the spleen and bone marrow of WT, Lyn−/−, and IgM−/− Lyn−/− mice was determined by intracellular staining of IgM, IgD, and IgA. (C) Percentages in (B) multiplied by the fraction of live cells positive for CD138 in each tissue. Unswitched cells are positive for either IgM or IgD. Statistics correspond to unswitched plasma cell percentages; differences in IgA+ cells were not significant. (D) Serum IgM in 16-week-old mice was quantified for B6.IgHa (WT) and Lyn−/− mice by ELISA. A sample from an IgM−/− mouse is shown for reference. (E) Serum IgD in 16-week-old mice was quantified for IgM−/− and IgM−/− Lyn−/− mice by ELISA. A sample from a WT mouse is shown for reference. (F) Gating scheme for quantifying the unswitched splenic plasma cell composition of IgM+/− Lyn−/− mice. (G) Percentage of unswitched splenic plasma cells (CD138+B220loIgM/IgD+) from each locus in IgM+/− and IgD+/− mice on the Lyn−/− background. For (B) and (C), figures are representative of n = 4–5 mice of each genotype. For (D), values from n = 3 WT and n = 4 Lyn−/− mice are averaged. For (E), values from n = 3 IgM−/− and n = 4 IgM−/− Lyn−/− mice are averaged. For (F) and (G), n = 4–5 mice of each genotype were used. Welch’s t test was used to calculate p values, and mean ±SEM is displayed. *p<0.05, **p<0.01, ***p<0.001.

Figure 6—source data 1. Numerical data corresponding to Ets1 expression, plasma cell compartments, and serum IgM and IgD titers in Figure 6A-G.
Numerical data corresponding to Ets1 expression in Figure 6A. Numerical data corresponding to plasma cell compartments in Figure 6B–C. Numerical data corresponding to serum IgM titers in Figure 6D. Numerical data corresponding to serum IgD titers in Figure 6E. - Numerical data corresponding to plasma cell competition in Figure 6F and G.
elife-35074-fig6-data1.zip (49.6KB, zip)
DOI: 10.7554/eLife.35074.032
Figure 6—source data 2. Numerical data corresponding to Ets1 expression in splenic B cells in Figure 6A.
elife-35074-fig6-data2.xlsx (37.9KB, xlsx)
DOI: 10.7554/eLife.35074.033
Figure 6—source data 3. Numerical data corresponding to plasma cell compartments in Figure 6B–C.
elife-35074-fig6-data3.xlsx (42.7KB, xlsx)
DOI: 10.7554/eLife.35074.034

Figure 6.

Figure 6—figure supplement 1. BCR signaling in Lyn−/− peritoneal B cell subsets.

Figure 6—figure supplement 1.

(A) Intracellular Erk phosphorylation in peritoneal B220+ B cells stimulated with anti-Igκ for 5 min. B1a (CD5+CD23-); B2 (CD5-CD23+). Histograms in (A) are representative of cells from n = 2 WT and Lyn−/− mice.
Figure 6—figure supplement 2. Lyn restrains unswitched plasma cell differentiation of follicular B cells.

Figure 6—figure supplement 2.

(A) Model: Lyn restrains BCR signaling in Fo B cells. Loss of Lyn leads to Btk-dependent downregulation of Ets1 expression and consequent expansion of unswitched (IgM+) plasma cells.