Figure 7.

Autophagy is necessary for survival of long-lived plasma cells during autoimmune responses. Mice harbouring the lpr mutation on the C57BL/6 background were crossed with Atg5^f/− CD21 cre mice (CD21 cre^lpr/lpr). They were compared with littermate Atg5^f/+ CD21 cre mice, also crossed with lpr mice (littermates^lpr/lpr), at the age of 9 months. (a) Individual values for each mouse assayed for absolute IgG and IgM concentrations in the serum, determined by ELISA and titres of anti-dsDNA IgM and IgG Abs. Means and SEM are represented (at least four mice in each group). (b) The spleens of the animals were collected, cells were stained by anti-CD19, anti-CD138, and anti-B220 Abs, and analysed by flow cytometry. Each point represents the value for an individual mouse. The central bar represents the means and the upper and lower bars symbolize the S.D. (c) Staining of bone marrow cells collected from one femur per mouse. Each dot plot stands for one representative case for each genotype. On the left, the gate delimiting B220⁻CD138⁺ cells should indicate the percentages of plasma cells resident in the bone marrow (surface). In the middle, results obtained after an intracellular staining of IRF4 molecule performed after surface staining of the previous markers (+intra). The red population corresponding to CD138⁻ cells is IRF4^low or IRF4^int. The CD138⁺ blue population corresponding to plasma cells is IRF4^hi. This latter staining was performed on four littermate^lpr/lpr mice and one CD21 cre^lpr/lpr mouse. (d) Percentage of plasma cells among the bone marrow cells for individual mice analysed as in (c). n=10 for littermates^lpr/lpr and n=6 for CD21 cre^lpr/lpr. Mean and S.D. are indicated. **P<0.01, ***P<0.001 (Mann–Whitney U-test)