Depletion of Tregs leads to a reduction of the CNS infection.

<p>(<b>A</b>) Adult DEREG (DEREG^−/+) mice were i.p. injected with 1 µg diphtheria toxin (DT) or with an appropriate volume of PBS (ctrl) at 6 consecutive days and analyzed the next day. Lymphocytes were isolated from the spleen and LN (6 cervical, 4 axillary, and 2 inguinal). FACS dot plot examples for regulatory CD4⁺ Foxp3-GFP⁺ T cells in the lymph nodes (left panels), and a quantitative evaluation of Foxp3-GFP⁺ T cells (percentage of all lymphocytes, right panel) from spleen and LN (mean values ± SEM, n = 4, P<0.01) are shown. (<b>B</b>) Experimental setup for the treatment of young MV-infected DEREG mice with DT at day 17, 18, and 20 post infection and analysis at 28 dpi. (<b>C</b>) Quantitative evaluation of the number of infected eGFP⁺ cells at 28 dpi in DEREG (DEREG^−/+) and control (DEREG^−/−) mice both infected i.c. with rMV-green and treated with DT. The reduction of mean values from 50 to 8 was significant, with P = 0,0098. The number of infected eGFP⁺ cells per brain was determined by microscopic evaluation of 100 µm sections through the complete cerebrum as described <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0033989#pone.0033989-Schubert1" target="_blank">[33]</a>.