Figure 4: Loss of MZ B-cell functions and bacterial infection after experimental stroke. | Nature Communications

Figure 4: Loss of MZ B-cell functions and bacterial infection after experimental stroke.

From: Adrenergic-mediated loss of splenic marginal zone B cells contributes to infection susceptibility after stroke

Figure 4

(a) Fluorescently labelled model antigen (red, PE-anti-CD21) is trapped by MZ B cells in the spleens of naïve and sham-operated animals 1 h after i.v. injection however little is detected in the MZ of mice recovered 2 days after MCAO. (b) Immunolabelling demonstrates that the loss of MZ B cells (as described Fig. 2) at 2 days after MCAO does not result in a loss of expression of the c-type lectin SIGN-R1 (red) by MZ macrophages (green, MARCO). (c) Quantification of the percentage area of PE-anti-CD21 per 846.28 μm2 image confirms a significant reduction of PE-anti-CD21 trapping in mice 2 days after MCAO in comparison to sham-operated animals. (d) MZ macrophage-targeted antigen (green, Dextran FITC) is trapped by MARCO+ MZ macrophages in the spleens from animals recovered from both MCAO and sham surgery and in naïve controls at 1 h post injection (Supplementary Fig. 4). Dextran-FITC remains associated with MZ macrophages (red, MARCO) 24 h post injection and has efficiently transported to the follicle where it co-localises with FDC networks (red, CD21/35) in all experimental groups. (e) Quantification of the percentage area of Dextran-FITC per 846.28 μm2 image confirms there is no significant difference in Dextran-FITC trapping in spleens from mice 2 days after MCAO in comparison to sham-operated controls (naïve n=3, sham n=3, MCAO n=6). (f) Reduced concentration of circulating IgM 2 days after MCAO in comparison to sham-operated controls (naïve n=4, sham n=4, MCAO n=9). Spontaneous bacterial infection occurs in both the lung (g) and blood (h) of mice from 1 day after MCAO onwards but cannot be found in sham-operated cage mates (sham n=4, 1d n=4, 2d n=9, 5d n=5, 7d n=7). Description of the frequency of infection in the lung (i) and blood (j) of mice for each recovery time point. Scale bars (a,d; top panel) 200 μm; (b,d; bottom panel) 50 μm. Data show (f) median±min to max value+s.d., *P<0.05 Mann–Whitney test; (c,e,g,h) mean+s.d., One-way ANOVA with Bonferroni correction comparing all groups to sham *P<0.05, **P<0.01, ***P<0.001.

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