TABLE 3.

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

Time of exposure to osmolarity (h)a	Uptake (% of initial inoculum) of M. tuberculosis under conditions of osmolarity				Uptake (%) under conditions of osmolarity (0.3 M dextrose)b with:
	Isoosmolarc	0.1 M dextrose	0.2 M dextrose	0.3 M dextrose	10% Serum	No serum
1	19 ± 6	17 ± 4	19 ± 2	19 ± 5	ND	ND
2	21 ± 4	19 ± 6	20 ± 4	23 ± 4	ND	ND
4	20 ± 6	19 ± 4	22 ± 3	22 ± 6	25 ± 5	18 ± 2
24	20 ± 3	21 ± 5	18 ± 5	21 ± 4	ND	ND

^aM. 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.

^bBacteria (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.

^cP > 0.05 for all comparisons with uptake of M. tuberculosis incubated under isoosmolar conditions.