Aortas from genetically altered young mice (6-8 weeks of age) were used to identify the MyD88 expressing cells that contribute to the basal IL-6 response. Aortas were harvested from young wild type and Myd88-/- mice and IL-6 measured in the culture supernatants (A). CD11c-Myd88 Tg mice are Myd88-/- except in CD11c+ cells and were compared to wild type controls (B). The aortas of LysMCre/MyD88-flox mice, which are Myd88-/- in Lysm+ cells, were compared to their LysM-Cre-/-/MyD88-flox Cre negative control (C). Rag-/- mice lack mature T cells and B cells and aortas of these mice were compared to wild type controls (D). SM22α-Cre/MyD88-flox are MyD88 deficient in smooth muscle cells and were compared with their Cre negative control (E). IL-6 levels were measured by ELISA. Differences between groups were analyzed using Student's t-test, n = at least 4 mice/group/experiment. *, P<0.05; **, P<0.01. The data shown are representative of three independent experiments.