FIGURE 4. CD73 inhibits IL-10 production from polymorphonuclear leukocytes (PMNs) following pneumococcal infection.

(A) PMNs from the indicated mouse strains were incubated for 45 min at 37°C with S. pneumoniae pre-opsonized with homologous sera or mock treated with buffer and homologous sera (uninfected) in vitro. The supernatants were then collected and assayed for IL-10 production by ELISA. (B) PBS control or adenosine (100 μM) were added to the PMNs 30 min prior to in vitro infection and the fold-change in IL-10 production was calculated by dividing the values of infected reactions by uninfected controls for each condition. Data were pooled from three separate experiments (n = 3 mice) with each condition tested in triplicate per experiment. Asterisks indicate significant differences determined by Student’s t-test. (C-E) Wild-type C57BL/6 or CD73^−/− mice were mock-infected or intratracheally (i.t.) challenged with 5 × 10⁵ CFU of S. pneumoniae. Six (grey bars) and 18 h (black bars) following challenge, (C) the percentage of IL-10-producing PMNs (Ly6G+), (D) the mean florescent intensities (MFI) of IL-10 in PMNs (Ly6G+), and (E) the number of IL-10-producing PMNs (Ly6G+) recruited into the lungs were determined by intracellular cytokine staining and flow cytometry (see Section 2). Pooled data are from three separate experiments (n = 6–9 mice per strain per time point). Student’s t-test are indicated by asterisks