Figure 3.

ACKR4 limits early B cell responses in a B cell–intrinsic manner. (A) Mixed BM chimeras were generated with an equal mixture of B6.Ly5.1 (CD45.1) and WT or Ackr4^−/− (both CD45.2) BM. Representative plots of CD45.2⁺ cells among Fo B cells (B220⁺IgD⁺Fas⁻GL7⁻), GC B cells (B220⁺IgD⁻Fas⁺GL7⁺), and early PBs (B220^lo/-CD138⁺) 5 d after SRBC. Gating of these populations is shown. Competitive ratios of GC B cells (left graph) and early PBs (right graph) are plotted as the frequencies of CD45.2⁺ cells in each compartment, normalized to the frequencies of CD45.2⁺ cells in the concurrent Fo B cell compartment. n = 6 mice/genotype (means ± SEM). (B) WT (CD45.1/2) and Ackr4^−/− (CD45.2) SW_HEL B cells were cotransferred into B6.Ly5.1 (CD45.1) mice and immunized with HEL^2X-SRBC (n = 4 mice) or mock-conjugated SRBCs (n = 3 mice). Contribution of WT and Ackr4^−/− cells to SW_HEL GC B cell (B220⁺Igκ⁺HEL^intGL7⁺CD138⁻), early PBs (B220^lo/-Igκ⁺HEL⁺CD138⁺), and B220⁺HEL^hiGL7⁻ (also Igκ⁺CD138⁻) cell populations 5 d after immunization. The SW_HEL.Ackr4^−/− competitive ratio is plotted as the ratio of Ackr4^−/− to WT among SW_HEL effector cell compartments from day 5 HEL^2X-SRBC–immunized mice, normalized to the input ratio (as determined from mock-SRBC immunized mice analyzed on day 5 [means ± SEM]). (C) Cd23^Cre/+.Rosa26^LSL-Ackr4/+ mixed BM chimeras were generated and analyzed as in A (n = 6–7 mice/genotype; mean ± SEM). (A–C) Data are representative of two (B and C) and three (A) independent experiments. Two-tailed, unpaired Student’s t test. ***, P < 0.001; ****, P < 0.0001.