bacterial pellet was then resuspended in HBSS, adjusted to a McFarland number 1 tube, and diluted in RPMI-1640 medium with 1% FBS ML323 cost serum in the absence of antibiotics to reach the necessary bacteria-to-cell ratio. Survival of intracellular bacteria A suspension of B cells adjusted to a concentration of 2 × 106 cells/mL was prepared as described previously. The cells were infected with each bacterial suspension (M. tuberculosis, M. smegmatis, and S. typhimurium) and maintained at 37°C in a CO2 atmosphere. After 2 h, the non-internalised bacteria were removed by low speed centrifugation (1,000 rpm for 5 min), the supernatant was discarded, and the cells were suspended in HBSS. After this procedure was repeated three times, the cellular pellet was suspended in RPMI-1640 with 1% FBS, and 20 μg/mL of amikacin (Sigma); after two h, the concentration of amikacin was decreased to 10 μg/mL to
eliminate any selleck chemical extracellular bacteria; in the latter medium, the cells were incubated for 12, 24, 48, and 72 h after infection with M. smegmatis and M. tuberculosis and for 6, 12, 18, and 24 h after infection with S. typhimurium. After each time point, the cells were washed three times with HBSS using low-speed centrifugation (1,000 rpm). To determine the number selleck compound of intracellular bacteria, the washed cell pellet was lysed and resuspended in 500 μL of sodium dodecyl sulphate (SDS) (0.25%); after 3 min, 500 μL of 5% bovine serum albumin (BSA) was added. The cell lysates were collected and maintained frozen at −70°C. To determine the colony-forming units (CFU), serial dilutions of the samples that were infected with M. tuberculosis and M. smegmatis were plated on Middlebrook 7H11 agar; similarly, the serial dilutions of the samples infected with S. typhimurium were plated on Luria agar. Bacterial and fluid-phase uptake by B cells An aliquot of B cells
in log-phase growth was centrifuged at 1,000 rpm and washed three times with HBSS. After the cell viability was determined using trypan blue dye, the suspension Carnitine palmitoyltransferase II was adjusted to a concentration of 2 ×106 cells/mL in RPMI-1640 with 1% FBS and 0.1 mg/mL dextran-FITC 70 (Sigma). The set of experiments on fluid-phase uptake were settled under the following conditions: (a) 1.0 μg/mL phorbol 12-myristate 13-acetate (PMA) (Sigma), (b) bacterial supernatant diluted by 1:10 in RPMI-1640, (c) M. smegmatis at a multiplicity of infection (MOI) of 10:1 and (d) M. tuberculosis at an MOI of 10:1, (e) S. typhimurium at an MOI of 20:1, and (f) control medium. In a 96-well sterile culture plate, a total of 200,000 treated cells were seeded in each well. The following procedure was followed for each condition: (1) quadruplicate samples were settled; (2) the plate was incubated at 37°C in a CO2 atmosphere; (3) after 15, 60, 90, 120, and 180 min, the fluid-phase excess was removed by centrifugation; (4) the cells were washed three times with HBSS; and (5) the washed cells were resuspended in 100 μL of HBSS.