Table II.

Lethal infection increases binding and internalization of L. monocytogenes by Ly-6C^highCD11b⁺ BM monocytes

Condition	Monocytes Associated with Bacteria (%)a	Bacteria/Monocyte	Intracellular Bacteria (%)b
Steady state	5.31 ± 1.76	1.54 ± 0.54	4.0 ± 2.4
Sublethal	4.04 ± 2.01	1.01 ± 0.03	1.0 ± 1.3
Lethal	10.19 ± 1.77*	3.29 ± 0.68*	25.2 ± 1.6*
Lethal controlc	1.60 ± 1.15	1.94 ± 0.92	96.4 ± 3.6*

Ly-6C^highCD11b⁺ BM monocytes were sorted by flow cytometry from steady-state animals or from animals infected 72 h earlier with sublethal (2.5 log10) or lethal (4.3 log10) amounts of L. monocytogenes. Cells and bacteria were mixed 1:15 in the presence of 10% normal mouse serum. Intracellular bacteria and extracellular bacteria bound to cells were differentially labeled and then quantified by fluorescence microscopy.

^aResults presented are the mean +/− SEM from 4–8 individual mice per group.

^bCalculated as (intracellular bacteria/total bacteria) × 100.

^cNo bacteria were added to cells from lethally infected mice.

^*p ≤ 0.02 compared with steady state; two-tailed Student t test.