Together, our results highlight the importance of epithelial-specific MyD88 signaling and demonstrate that although functional MyD88 signaling in DC and macrophages alone is sufficient to correct the phenotype of MyD88-deficiency, these cells do not seem to be essential for host protection in MyD88-sufficient animals during acute infection with C. difficile.
While myeloid differentiation factor 88 (MyD88) is also a crucial adaptor for most TLR signaling pathways, MyD88 deficiency had only a marginal impact on disease course.
All these responses were abrogated in mice with a general deficiency of MyD88 but unaltered in mice with MyD88 deficiency, specifically in myeloid or type II lung epithelial cells.
The comparison of disease development in mice carrying the hematopoietic cell-specific deletion of MyD88 (<i>Myd88<sup>fl/fl</sup>Vav-cre<sup>+</sup></i> mice) with mice carrying the total MyD88 deficiency (<i>Myd88</i><sup>-/-</sup> mice), we show that the progression of skin and systemic inflammation, as well as of epidermal thickening, was completely dependent on MyD88 expression in hematopoietic cells.
Because MyD88 is essential for the downstream signaling of all TLRs, except TLR3, we investigated the effects of MyD88 deficiency (MyD88-/-) on behavioral functions in mice.
As MyD88(-/-) BMDM exhibit low surface expression of dectin-1 after in vitro culture in rMCSF, differences in dectin-1 dependent, MyD88-independent signaling may account for some of the phenotypes currently ascribed to MyD88-deficiency alone.