Figure 3. MZB cells display activated phenotypes and serve as memory-like B cells during Mtb infection.

Infected mice and corresponding mock controls were sacrificed at 4, 8, and 12 weeks post-infection, with uninfected mice serving as baseline controls (0 weeks). Single-cell suspensions of the lungs and spleen were analyzed by flow cytometry. The B cell subsets were gated according to Figure S1A.

(A and B) Expression patterns of CD86 and CD69 on B cell subsets. (A) Frequencies of CD86⁺ cells and (B) frequencies of CD69⁺ cells. Mean ± SEM, n = 4–6. Error bars are omitted if shorter than the symbols. Unpaired Student’s t test was used to determine the statistical differences between Mtb-infected and mock controls. *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001.

(C and D) Activated and memory-like phenotypes of B cell subsets in infected mice at 8 weeks post-infection. (C) Frequencies of CD86⁺, CD80⁺, and CD69⁺ cells and (D) frequencies of memory-like B cells (CD80⁺CD273⁺CD73⁺). Horizontal lines represent the mean, n = 4–6; one-way repeated-measures ANOVA with Bonferroni’s post hoc test was used to determine the statistical differences between subsets. *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001; ns, not significant.

(E) Absolute counts of memory-like B cells within B cell subsets in infected and mock-infected mice at 8 weeks post-infection. Horizontal lines represent the mean, n = 4. Unpaired Student’s t test was used to determine the statistical differences between Mtb-infected and mock controls. *p < 0.05, **p < 0.01, ***p < 0.001; ns, not significant.

The results shown are representative of three independent experiments.