Since we observed lower IL‐10 levels in the spleen and lung of Sema3E-Fc treated mice and Treg is one of the primary sources of this cytokine, we next examined CD4+ CD25+ Foxp3+ T cells in the lungs of WT and Sema3E KO mice treated with Sema3E-Fc following Cm infection. This evidence concerns the gene IL10 and infection.