FRs are expressed on F4/80⁺ macrophages recruited by inflammatory stimuli, but not on resident peritoneal F4/80⁺ macrophages. The percentage of FR⁺ cells within the F4/80⁺ macrophage population isolated from the peritoneal cavities of mice treated with thioglycolate, live bacteria, heat-killed bacteria (P aeruginosa), zymosan, or sterile PBS is shown. Pairwise comparisons using t tests with pooled SD were used for statistical analysis; ***P < .001, *P < .05. HK-bacteria indicates heat-killed bacteria.