TABLE 3.

Uptake of M. tuberculosis by human monocyte-derived macrophages following exposure to hyperosmolar conditions

Time of exposure to osmolarity (h)aUptake (% of initial inoculum) of M. tuberculosis under conditions of osmolarityUptake (%) under conditions of osmolarity (0.3 M dextrose)b with:
Isoosmolarc0.1 M dextrose0.2 M dextrose0.3 M dextrose10% SerumNo serum
119 ± 617 ± 419 ± 219 ± 5NDND
221 ± 419 ± 620 ± 423 ± 4NDND
420 ± 619 ± 422 ± 322 ± 625 ± 518 ± 2
2420 ± 321 ± 518 ± 521 ± 4NDND
  • a M. tuberculosis H37Rv cultured in 7H9 broth was exposed to different conditions for 1, 2, 4, or 24 h. After exposure, the bacteria were centrifuged at 4°C and resuspended in RPMI 1640 with 10% heat-inactivated autologous serum, and the concentration was adjusted to 5 × 106 bacteria/ml (MOI of 10). Phagocytosis was carried out for 1 h. Results using an MOI of 1 were similar and are not shown. The experiment was repeated four times. Results are means ± standard deviations.

  • b Bacteria (5 × 106) were incubated under conditions hyperosmolarity for 4 h prior to the assay. Then, the bacteria were washed at 4°C and incubated with macrophages in the absence or presence of 10% serum for 1 h. The uptake of bacteria cultured under laboratory conditions by macrophages increased from 16% ± 3% to 24% ± 4% of the inoculum (P < 0.05). ND, not done.

  • c P > 0.05 for all comparisons with uptake of M. tuberculosis incubated under isoosmolar conditions.