(A) Intracellular detection of NOD2 (bold line in the histogram plot) was performed by flow cytometry using freshly isolated alveolar macrophages selected from a gate set on large granular bronchoalveolar cells (R1, dot plot). One representative experiment out of three experiments is presented.
(B) Cells were stimulated with 10 μg/mL of MDP for 24 h, and NOD2 and IκBα proteins were measured in the cytosolic fractions by western blot analysis. The fold increase relative to unstimulated cells and normalized to tubulin of one representative experiment out of three is reported.(C) The upregulation of NOD2 gene expression was assessed by quantitative PCR. The results are depicted as the mean fold change in NOD2 gene expression relative to unstimulated cells (n = 11).(D) Subcellular localization of NOD2 was ascertained in unstimulated (left, ×80,000) and MDP‐stimulated cells (right, ×63,000) using an anti‐NOD2 antibody and detected with a secondary antibody coupled to 5‐nm gold particles, indicated with arrowheads. Bar represents 150 nm. Micrographs were obtained from one experiment.

NOD2 ligation in alveolar macrophages induces pro‐inflammatory cytokine release. Cells were incubated for 24 h in the presence of 10 μg/mL of MDP or 100 ng/mL of LPS. Production of IL‐1β, IL‐6, TNF‐α, and IL‐10 was measured in culture supernatants using Milliplex technology. Depicted are box plots with median values and quartiles for each cytokine. The data are representative of two independent experiments (n = 11); *p 0.05 and **p 0.01 using the two‐tailed Wilcoxon signed‐rank test.

LL37 and IRGM gene expression is upregulated following NOD2 activation (A‐D). Alveolar macrophages were incubated in the presence of 10 μg/mL of MDP or 100 ng/mL of LPS for 24 h. Upregulation of (A) LL37 and (D) IRGM gene expression was assessed after specific ligand recognition by quantitative PCR using the Taqman system and the ΔΔCT method for relative quantification. The fold change in gene expression relative to unstimulated cells is depicted. Data are representative of two independent experiments (n = 7-12). Bold lines indicate median values.

(B, E) LL37 and IRGM protein levels were measured in cytosolic fractions by western blot analysis.(C, F) Data are expressed as the protein fold increases relative to unstimulated cells and normalized to tubulin calculated by densitometry and are shown as means ± SEM. One representative experiment out of three experiments is presented.(A) Intracellular bacterial burden was measured by quantifying CFU, and the intracellular growth index was calculated after 1 and 4 days post infection relative to phagocytosed bacteria at day 0. Data are shown as medians and quartiles and are representative of n = 7 experiments.

The production of (B) TNF‐α, (C) IL‐6 and (D) IL‐1β was measured in culture supernatants using Milliplex technology. Box plots depicting median values and quartiles are representative of n = 9 experiments.

(E) LL37 and (F) IRGM gene expression was assessed by quantitative PCR using the Taqman system and the ΔΔCT method for relative quantification. Fold changes in gene expression relative to unstimulated cells are reported. Bold lines indicate median values of n = 9. *p 0.05 and **p 0.01 using the two‐tailed Wilcoxon signed‐rank test.

(G) LL37 and IRGM protein was assessed by western blot. One representative experiment out of three experiments is presented.(H) The amount of protein normalized to tubulin relative to infected‐only cells was calculated by densitometry. Data are depicted as the means ± SEM and are representative of n = 3 experiments.(A, B, D, E, G, H) The subcellular localization of autophagy proteins was ascertained in untreated and MDP‐treated cells using (A, B) anti‐IRGM, (D, E) anti‐LC3, and (G, H) anti‐ATG16L1 antibodies and detected with a secondary antibody coupled to 5‐nm gold particles indicated with arrowheads; bar represents 150 nm.(C, F, I) Gold particles co‐localizing with bacteria were manually counted in ten macrophages of each condition. Means ± SEM are depicted and differences between treatments are indicated, *p 0.05 using a two‐tailed paired t‐test. (B) Transmission electron microscopy (TEM) magnification ×50,000; the rest of the micrographs are TEM magnification ×80,000. Data were generated from one experiment.

Macrophages treated with MDP after M. tuberculosis infection develop autophagy vacuoles. Alveolar macrophages were infected with M. tuberculosis H37Rv at an MOI of 5 for 1 h. Nonphagocytosed bacteria were washed away, and the macrophages were incubated for an additional hour. The cells were then treated with 10 μg/mL of MDP for 24 h. Autophagy indicators (arrowheads) such as (A) vesicles containing organelles (TEM magnification ×20,000) and (B) onion skin‐like lamellar multivesicular bodies (TEM magnification ×16,000) were identified by ultrastructural analysis..

(C, D) Autophagosomes containing mycobacteria (Mtb) are indicated with arrows (C, TEM magnification ×40,000; D, TEM magnification ×12,000). Micrographs were obtained from one experiment. Bar represents 300 nm.