Selective deficiency of CD4⁺ cDCs in the spleen of SIRPα MT mice. (A-B) Splenocytes from WT or SIRPα MT mice were incubated with a biotin-conjugated mAb to CD4. The cells were also stained with an FITC-conjugated mAb to CD8, PE-conjugated streptavidin, an APC-conjugated mAb to CD11c, an APC-Cy7–conjugated mAb to B220, and propidium iodide (PI). The expression of CD11c and B220 on PI-negative cells (A) or that of CD4 and CD8 on CD11c^high B220^– cells (cDCs; B) was analyzed by 5-color flow cytometry (left panels). The relative numbers of cDCs and CD11c^int B220⁺ cells (pDCs; A) or those of CD4⁻CD8⁺ (CD8⁺ cDCs), CD4⁺ CD8⁻ (CD4⁺ cDCs), and CD4⁻CD8⁻ (DN cDCs) cells (B) are expressed as a percentage of all viable splenocytes (A) or cDCs (B) on each plot. The absolute numbers of cDCs and pDCs (A) and of CD8⁺ cDCs, CD4⁺ cDCs, and DN cDCs (B) in the spleen were also determined (right panels); data are means ± SE for 4 mice per group and are representative of 5 independent experiments. **P < .01 (Student t test). (C) Frozen sections of the spleen from WT or SIRPα MT mice were stained with an FITC-conjugated mAb to B220 (green, left panels) or to Thy1.2 (green, right panels) as well as with a biotin-conjugated mAb to CD11c and Cy3-conjugated streptavidin (red). Images were visualized with a BX-51 microscope equipped with a 10×/0.4 numeric aperture objective lens (Olympus) and a DP71 camera (Olympus), were analyzed with DP controller software (Olympus), and were processed with Adobe Photoshop CS2 software (Adobe Systems). Data are representative of 3 separate experiments. Areas of white pulp are demarcated by dotted lines. B and T represent B- and T-cell areas, respectively. Scale bar, 200 μm.