Ly-6C^lo or Ly-6C^hi monocytes in WT mice were labeled with latex (24). (A) The appearance of latex⁺ cells in the peritoneal cavity was monitored by flow cytometry using F4/80 and CD115 antigens to identify monocytes and macrophages. Macrophages are seen as the prominent F4/80^hi population in the noninflamed peritoneum (left dot plots). They become outnumbered by numerous infiltrating monocytes (inflamed plots; lower levels of F4/80 in lower right quadrants) and F4/80^–CD115^– neutrophils (inflamed plots; lower left quadrants). Note that Ly-6C^hi labeling of monocytes leads to both latex⁺F4/80⁺ monocytes (inflamed plots; upper right quadrants) and latex⁺F4/80^– neutrophils (inflamed plots; upper left quadrants) appearing in the peritoneum, since some neutrophils transiently carry latex in this labeling protocol (24). In the inflamed peritoneum, latex⁺Ly-6C^hi monocytes outnumbered latex⁺ neutrophils 4:1, even though neutrophils dominate in acute peritoneal inflammation, in contrast to what occurs in atherosclerosis. (B) The graph shows the actual frequency of latex⁺ Ly-6C^lo or Ly-6C^hi monocytes in the inflamed peritoneum (gray bars), determined by flow cytometry, compared with the expected/known frequency (white bars) at which they would enter the peritoneum as unlabeled cells (“expected” data are derived from previously published calculations [ref. 16], as described in Methods). n = 4 mice per group. Differences between the actual and expected frequencies were not significant. (C) Levels of plasma cytokines (± SD) were measured at baseline or 2, 12, and 24 hours after administration of latex in the Ly-6C^hi or Ly-6C^lo monocyte labeling protocol. n = 3 mice per time point.