T cells are a biologically relevant IL-10 source.

<p><i>Il-10</i>^−/−, <i>Il-10</i>^fl/flx<i>CD4-Cre</i>⁺, <i>Il-10</i>^fl/flx<i>CD4-Cre</i>⁻ and C57BL/6 mice were infected with Clone 13. Virus titers were determined in (A) spleen, (B) kidney, (C) liver and (D) lung on day 10 or 12 post infection. Each symbol represents one individual mouse; the solid lines represent the geometric means, the dashed line the detection limit. The numbers indicate how many mice per total mice exhibited virus titers below 10³ in spleen and kidney, 5×10³ in liver and 10⁴ in lung. Statistical significance was determined with the Mann-Whitney test. (E and H) TNF-α production by CD8⁺ T cells in lung mononuclear cells was determined after 5 hours stimulation with the peptide gp33. TNF-α secretion by CD4⁺ T cells in (F and I) lung mononuclear cells and (G and J) splenocytes was determined after 5 hours stimulation with the peptide p13. Mean and standard deviation of the (E–G) percentages and (H–J) total numbers are shown. Statistical significance was determined with unpaired 2-tailed Student's t test. A summary of all mice from two independent experiments with 3–8 mice per group is depicted. * p<0.05; ** p<0.01; *** p<0.001; *** p<0.0001.