TABLE 2.

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

Time of exposure to anaerobiosis (h)a	Uptake (% of initial inoculum) of M. tuberculosis		Uptake (%) under anaerobiosisb with:
	Anaerobiosis	Control (20% O2)	10% Serum	No serum
1	19 ± 6	16 ± 4	ND	ND
2	32 ± 4c	17 ± 5	ND	ND
4	61 ± 8c	20 ± 6	51 ± 5	53 ± 6
24	53 ± 12c	21 ± 5	ND	ND

^aM. tuberculosis H37Rv cultured in 7H9 broth was exposed to anaerobiosis for 1, 2, 4, and 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 anaerobiosis 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 compared with uptake of M. tuberculosis incubated under 20% oxygen tension.