Monocytes give rise to macrophages within the liver during infection.

<p><b>A</b>. Ly6C^hi monocytes sorted from liver of infected mice differentiate into macrophages following culture with M-CSF: a cytospin of macrophages grown in this way is shown (left panel) along with flow cytometric analysis of the same cells vs. macrophages or Ly6C^hi monocytes sorted from infected liver (<i>ex vivo</i>) for expression of MertK and CD64 (right panel). This experiment was repeated three times with similar results. <b>B</b>. The expression of GFP in blood monocytes (Ly6C^hi CD11b⁺) from naïve mice, and on CD64⁺MertK⁺ macrophages from naïve or infected <i>C</i>x<i>₃cr1^gfp/+</i> mice. Data are from cells pooled from 3 individual mice, and are representative of two independent experiments. <b>C</b>. BrdU is rapidly incorporated into monocytes and appears in macrophages only later following initiation of labeling. Infected mice were injected with BrdU and bone marrow, blood, and hepatic leukocytes collected at the times shown were pooled and monocytes and macrophages (Mphi) were stained for incorporated BrdU. Results are data from one independent experiment with three to five mice per group, and are representative of 3 independent experiments. <b>D</b>. BrdU incorporation into peritoneal macrophages in mice injected i.p. with IL-4/anti-IL-4 complexes. Data are concatenated from 3 mice per group and are representative of 2 independent experiments. <b>E</b>. Within the entire BrdU labeled hepatic leukocyte population, CD64⁺ Siglec-F^hi macrophages initially represent only a small percentage of all cells, but over time post-labeling come to represent 75% of the labeled population (by day 7). In these plots, monocytes fall within the indicated CD64^int Siglec-F^Neg gate; these data are from the experiments described in C.