We have reported that CD3+CD4+IL-10+ T cells are the main source of the immunoregulatory cytokine in the respiratory tract during the course of viral infection (Chiba et al., 2013; Zelaya et al., 2014) and that the improvement of this immune cell population is mediated by the secretion of IL-6 and IL-27 by alveolar macrophages (submitted for publication, Figure 3). Here, IL10 is linked to viral infectious disease.