Figure 1: Kinetics of acute zymosan-induced peritonitis and appearance of Ly-6B-expressing inflammatory macrophages (MØ).

(a) Graphs showing the numbers of neutrophils and eosinophils (left panel) and MØ (both total monocyte/MØ and Res MØ) MØ (right panel) present at the indicated times after i.p. administration of 2 × 10⁶ zymosan particles. Data represent mean±s.e.m. of 3–5 individual mice per time point, taken from one of two similar experiments. (b) Representative flow-cytometric profiles showing Ly-6B⁺ inflammatory (Inf) MØ, identified as previously described^6,18 by gating on CD11b^highF4/80^low-high cells (excluding eosinophils), are clearly distinct from Tim4^high Res MØ. Gates denote Ly-6B⁺ and Ly-6B⁻ Inf MØ populations. (c) Approximately a fifth of cells classified as Inf MØ are Ly-6B⁺ and are present for several weeks after induction of a mild inflammatory reaction. Data are taken from the animals represented in panel a above and presented as mean±s.e.m. (d) Representative flow-cytometric profiles (gated on F4/80^low-highCD11b⁺ monocytes and MØ) taken from mice 72 h after induction of peritonitis with zymosan (both 2 × 10⁶ and 2 × 10⁷ particles) and thioglycollate broth, as indicated. The higher dose of zymosan resulted in similar MØ populations, but with substantially reduced recoverable numbers of Res MØ when compared with the low dose, as expected^12,25. In contrast, thioglycollate broth resulted in a near complete depletion of Res MØ and no evident Ly-6B⁺ Inf MØ population at this time. The presence of both Ly-6B⁺ monocytes and Ly-6B⁺ Inf MØ populations are indicated. Flow-cytometric plots are representative of at least three mice per group from one of two similar experiments. (e) The Ly-6B-expressing MØ were gated as indicated (left panel) and purified (>90%) by flow-cytometric cell sorting and analysed on cytospins stained with eosin and methylene blue. Cells were pooled from 6-week-old female C57BL/6 mice 7 days after i.p. zymosan (2 × 10⁶ particles).