FcγR expression on red pulp macrophages is distinct from the expression on monocytes and monocyte-derived macrophages. (A) Overview of expression of the FcγR isoforms on autofluorescent CD163^highCD14^low red pulp macrophages from spleen, showing individual values. FcγRI (MoAb 10.1), n = 82; FcγRIIa (MoAb IV.3), n = 57; FcγRIIb (MoAb 2B6), n = 43; FcγRIIIa+b (MoAb 3G8), n = 82; FcγRIIIb (MoAb 5D7), n = 7. (B) Correlation of FcγRI expression on red pulp Mφ with FcγRI levels on neutrophils in the same spleen (n = 82). (C) Representative histograms on autofluorescent CD163^highCD14^low red pulp macrophages from spleen for FcγRI, FcγRIIa, FcγRIIb, and FcγRIIIa+b (blue line: specific staining, red shading: isotype control). (D) Comparison of flow cytometry stainings on nonautofluorescent CD163^intCD14^high spleen monocytes, CD14^high blood monocytes gated on FSC/SSC pattern, autofluorescent CD163^highCD14^low red pulp macrophages from spleen, and M-CSF and GM-CSF cultured monocyte-derived macrophages. FcγRI: n ≥ 24 for each group. FcγRIIa: n ≥ 10 for each group. FcγRIIb: n ≥ 15 for each group. To ensure specificity for FcγRIIb, only samples from individuals that cannot express FcγRIIc and with wild-type FCGR2B promoters are presented. FcγRIIIa+b: n ≥ 23 for each group. Mean ± SEM are shown for each group. (E) Quantitative mRNA analysis of various FCGR transcripts encoding FcγRs. The relative expression compared with the expression in pooled whole blood leukocytes, corrected for housekeeping genes, is shown for each transcript. Mean ± SEM of n = 3 are shown for each group.