SI Mfs are highly proficient at antigen uptake. (A) The percentage of pHrodo green E. coli⁺ cells among CD14⁺ PBMo, PBDC (left, n = 5), and SI Mf subsets and DCs (right, n = 5) was determined by flow cytometry after indicated incubation times. (B) The effect of preincubation with human serum (opsonization) on the uptake of pHrodo green E. coli bioparticles by SI Mf subsets and DCs was determined by flow cytometry after 15 or 45 min of incubation (n = 5). E. coli bioparticles were opsonized by incubating in 50% inactivated human serum for 30 min at 37°C. *, P < 0.05; ****, P < 0.0001 (two-way RM-ANOVA comparing effect of opsonization at one time point). (C) The percentage of DQ-OVA (green)⁺ cells among CD14⁺ PBMo, PBDC (left, n = 5), and SI Mf subsets and DCs (right, n = 5) was determined by flow cytometry after indicated incubation times. (A and C) Data are presented as mean ± SEM of pHrodo⁺ (A) or DQ-OVA⁺ (C) cells within each population (Fig. S4 A). Comparisons between subsets are marked in color corresponding to compared subset. *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001 (two-way RM-ANOVA).