Figure 1
Figure 1. FcμR is highly expressed by CLL cells compared with healthy B and T cells. FcµR (FAIM3) is detected on the surface of FcµR-positive cell lines, healthy donor PBMCs, and patients’ CLL cells by mAbs. (A) Cell line 293 was genetically modified to express FcμR; cells (FcµR+ 293, FcµR—293, and Mec-1; 0.5 × 106 cells each) were stained with the anti-FcµR mAb (clone 6B10), anti-FAIM3 mAb, anti-FAIM3 mAb (clone 1E4), and the anti-FcµR mAb (clone HM14) (bold lines) or the respective isotype-matched control antibodies (gray histograms). (B) The anti-FcµR mAb 6B10 does not compete in binding with the other anti-FcμR mAbs. FcµR+ 293 cells were incubated with a 20-fold excess of the competitor antibody, stained with the labeled staining antibody as indicated, and recorded by flow cytometry. Competition was calculated as follows: competition (%) = 100 – maximal binding. The 6B10 mAb does not compete in binding with the FAIM3, FAIM3 1E4, or HM14 antibody, whereas HM14 competes with the FAIM3 and the FAIM3 1E4 mAb. (C) CLL cells from 3 patients (#1, #2, #3) were recorded for FcμR by flow cytometry. Isolated cells (0.5 × 106 cells) were stained with the anti-CD5 mAb and the anti-CD19 mAb. CD19+CD5+ CLL cells were analyzed for FcµR by various anti-FcµR antibodies (bold line) or isotype-matched control antibodies (gray histograms). (D) FcµR is preferentially expressed by healthy CD19+ CD5− B cells and less by CD19− CD5+ T cells. PBMCs from healthy donors (n = 4; 0.5 × 106 cells) were stained with the anti-CD5 mAb and the anti-CD19 mAb. The cell subpopulations (CD19+CD5−, CD19−CD5+, CD19−CD5−) were recorded for FcµR using the respective antibodies. Isotype-matched control antibodies served as control. Bars represent the MFI of FcµR staining. Statistic analysis was performed using the Student t test (*P < .05; **P < .01; ***P < .001). (E) CLL cells (n = 14) and healthy donor B cells (n = 14) were recorded by flow cytometry for FcμR by staining with the mAb 6B10. The FcμR MFI on healthy B cells was set to 1, and the respective FcμR levels were calculated (relative levels). CD19 was recorded on CLL cells (n = 5) and healthy donor B cells (n = 7), and the MFI was shown. Statistical analysis was performed using the Student t test (FcμR, **P = .0051; CD19, **P = .002).

FcμR is highly expressed by CLL cells compared with healthy B and T cells. FcµR (FAIM3) is detected on the surface of FcµR-positive cell lines, healthy donor PBMCs, and patients’ CLL cells by mAbs. (A) Cell line 293 was genetically modified to express FcμR; cells (FcµR+ 293, FcµR—293, and Mec-1; 0.5 × 106 cells each) were stained with the anti-FcµR mAb (clone 6B10), anti-FAIM3 mAb, anti-FAIM3 mAb (clone 1E4), and the anti-FcµR mAb (clone HM14) (bold lines) or the respective isotype-matched control antibodies (gray histograms). (B) The anti-FcµR mAb 6B10 does not compete in binding with the other anti-FcμR mAbs. FcµR+ 293 cells were incubated with a 20-fold excess of the competitor antibody, stained with the labeled staining antibody as indicated, and recorded by flow cytometry. Competition was calculated as follows: competition (%) = 100 – maximal binding. The 6B10 mAb does not compete in binding with the FAIM3, FAIM3 1E4, or HM14 antibody, whereas HM14 competes with the FAIM3 and the FAIM3 1E4 mAb. (C) CLL cells from 3 patients (#1, #2, #3) were recorded for FcμR by flow cytometry. Isolated cells (0.5 × 106 cells) were stained with the anti-CD5 mAb and the anti-CD19 mAb. CD19+CD5+ CLL cells were analyzed for FcµR by various anti-FcµR antibodies (bold line) or isotype-matched control antibodies (gray histograms). (D) FcµR is preferentially expressed by healthy CD19+ CD5− B cells and less by CD19− CD5+ T cells. PBMCs from healthy donors (n = 4; 0.5 × 106 cells) were stained with the anti-CD5 mAb and the anti-CD19 mAb. The cell subpopulations (CD19+CD5−, CD19−CD5+, CD19−CD5−) were recorded for FcµR using the respective antibodies. Isotype-matched control antibodies served as control. Bars represent the MFI of FcµR staining. Statistic analysis was performed using the Student t test (*P < .05; **P < .01; ***P < .001). (E) CLL cells (n = 14) and healthy donor B cells (n = 14) were recorded by flow cytometry for FcμR by staining with the mAb 6B10. The FcμR MFI on healthy B cells was set to 1, and the respective FcμR levels were calculated (relative levels). CD19 was recorded on CLL cells (n = 5) and healthy donor B cells (n = 7), and the MFI was shown. Statistical analysis was performed using the Student t test (FcμR, **P = .0051; CD19, **P = .002).

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