The presence of TNF-α and IL-10 in the culture supernatants was assessed using Quantikine ELISA kits. The sensitivities of TNF-α and IL-10 assays were 1.6 pg/ml and 3.9 pg/ml, respectively. Statistical analysis Data are presented as means ± SEMs. Statistical significance was verified using nonparametric Selleck MK 8931 Wilcoxon’s signed-rank or Mann–Whitney U tests. The Statistica 8.0 (StatSoft, Poland) software package was used for statistical calculations. Statistical significance was defined as p ≤ 0.05. Results Expression of CD14 on resting MØ In order to confirm that THP-1 cells in the presence of PMA were differentiated after 24 hours,

the surface expression of CD14 molecule was estimated. Similarly to other researchers [17, 18] we found that CD14 surface expression on monocytes (i.e., THP-1 cells prior to differentiation) was greater than on PMA-treated THP-1 cells (i.e., after differentiation to MØ), with MFI values of 99 ± 10 and 45 ± 7 (n = 6), respectively. MØ uptake of ∆kstD mutant and wild-type strains The percentage of resting MØ and IFN-γ-activated MØ involved in the uptake of Mtb strains

was approximately 30-40%. Moreover, both types of MØ ingested opsonized and non-opsonized wild-type and ∆kstD strains equally well (Figure  1A), and took up similar numbers of check details bacteria of both strains (Figure  1B). Figure 1 Ingestion of Mtb by MØ. Resting and IFN-γ-activated MØ were infected with FITC-labeled wild-type or ∆kstD strains for 2 hours. (A) IKK inhibitor Percentage of MØ infected with Mtb strains; (B) Percentage distribution of MØ with the counted number of bacteria engulfed by one phagocyte Interleukin-3 receptor (per MØ). Percentage of infected MØ was calculated according to the formula: MØ with bacteria *100/ number of counted MØ and expressed as means ± SEMs (n = 5). Mtb ops – bacteria opsonized, Mtb non-ops – bacteria

non-opsonized. Intracellular replication of wild-type and ∆kstD strains Initially, we compared the survival of the wild-type and ΔkstD strains in resting MØ 1, 2, 4, 6 and 8 days post-infection. The detachment of MØ monolayer was observed on day 8 and therefore this time point was excluded from the subsequent experiments. We did not observe differences in CFUs count at 1 and 2 days post-infection, therefore day 1 was also excluded from the subsequent experiments. As shown in Figure  2, the numbers of viable wild-type and ΔkstD bacilli were similar up to 2 days post-infection, slightly and insignificantly different up to 4 days and statistically different on day 6, suggesting differential growth of mutant and wild-type strains. To test this, we compared the intracellular replication of ΔkstD and wild-type Mtb in resting and IFN-γ-activated MØ 6 days after infection.