For Western blotting supernatants and sonicated preparations of wild-type M. tuberculosis H37Rv and the deleted and complemented strains were fractionated by SDS-PAGE and expression of the 19 kDa antigen compared by Western blot analysis using a polyclonal anti-19 kDa serum. Isolation and culture of monocytes Buffy coats from healthy donors were obtained from the National Blood Transfusion Service (Colindale, London, Y-27632 UK). Following dilution in RPMI (1/3 vol/vol), peripheral blood mononuclear cells (PBMC) were separated by centrifugation over Ficoll-Paque Plus (Pharmacia, Uppsala, Sweden). Cells were washed in RPMI and

counted. Cells were suspended at 1.2 × 107/ml in RPMI/10% FCS medium and aliquots of 25 mls were added to 150 cm2 tissue culture flasks. Flasks were placed flat in a 5% CO2 incubator and monocytes allowed to adhere for 2 h at 37°C. Non-adherent

cells were removed by washing 3 times with 10 mls of pre-warmed RPMI. Finally, 10 mls of ice-cold PBS was added and the flasks were incubated at 4°C for 20 mins. Using a scraper, monocytes were gently dislodged from the bottom of the flasks and pooled in a 50 ml Falcon tube to count. Cells were plated in RPMI containing 10% serum at 106/well in a 24-well tissue culture plate, and cultured overnight before infection. Infection of cells Bacilli used to infect cells were grown in Middlebrook 7H9 broth supplemented with ADC to mid-log phase Raf inhibitor review (OD 0.4–0.8) then frozen in aliquots in 15% glycerol. The CFU content of aliquots was determined by serial dilution and plating on Middlebrook 7H11 agar supplemented with OADC. Monocytes were infected at a multipliCity of infection of 1:1 without removing non-phagocytosed bacteria. Culture duration was Acyl CoA dehydrogenase 72 hrs., at which time supernatants were aspirated, 0.22 μm filtered, and stored at -80°C pending analysis by ELISA. ELISA Cytokine ELISA was performed using the DuoSet ELISA Development Systems (R&D Systems, Minneapolis,

MN) following the manufacturer’s recommendations. The sensitivity of the assays was 15 pg/ml for IL-12p40, 10 pg/ml for IL-1β and 50 pg/ml for TNF-α. Histone associated DNA fragments, released into tissue culture supernatant and interpreted as evidence of apoptotic cell death, were assayed by the cell death detection ELISA (Roche Applied Science, Lewes, Sussex, UK) according to the manufacturer’s instructions. Sequence analysis Homologues of the M. tuberculosis 19 kDa gene LpqH were identified by Blast searches of sequenced genomes [28]. Alignment of protein sequences was performed using Clustal W and results are displayed as a sequence pile-up and as a neighbour-joining tree. Strains and genome accession numbers: M. tuberculosis H37Rv, AL123456.2; M. smegmatis MC2155, CP000480.1; M. ulcerans Agy99, CP000325.1; M. marinum M, CP000854.1; M. leprae TN, AL450380.1; M. avium subsp. paratuberculosis K-10, AE016958.1; M. abscessus, CU458896.