IL-17A relays Nod1-dependent microbial signals to promote phagocyte longevity. (A) Frequency of IL-17A-producing CD45⁺ cells from the ilea of WT and Nod1^−/− mice after 3 injections of 100 µg C12-iE-DAP (Ligand) or vehicle control. (B) Gating strategy for analysis of IL-17A-producing ileal cells (WT example shown). (C) Quantification of IL-17A-producing ileal γδ T cells following treatment as in panel A. (D) Assessment of cellular lifespan ex vivo (Annexin V⁻, % Viable) among neutrophils (PMNs) and IMs. Survival of cells from the bone marrow (D, 24 hours) and spleens (E, 6 hours) was quantified for WT, neomycin-treated WT, and Nod1^−/− mice after 100 µg injections of IgG1 isotype control (Isotype) or neutralizing anti-IL-17A antibody (α-IL-17A), given 12 and 2 hours before euthanasia. (F) BrdU pulse-chase assays. Quantification of BrdU⁺ frequency among PMNs and IMs from the bloodstream of CNV (black), NEO (gray), and Nod1^−/− mice (open). Mice received injections of 100 μg of IgG1 isotype control (solid curves) or IL-17A-neutralizing antibody (hashed curves) on days 2 and 3 after administration of BrdU, with or without concurrent injections of 100 µg C12-iE-DAP (Ligand). BrdU⁺ frequency was assessed on days 2, 4, and 5 after BrdU injection. (G) Rate constants (k, day⁻¹) for 1-phase exponential decay quantified from BrdU⁺ frequencies depicted in (F). All data presented as mean ± SEM with ≥4 mice per group. Statistical significance was assessed by Student t test for pairwise comparisons and 1-way ANOVA with Newman-Keuls posttest for comparisons of >2 conditions. *P < .05; **P < .01; ***P < .001.