Fig. 4. Local ACKR4-generated chemokine gradients at the SCS direct migration of memory B cells.

a Frequency of QM ACKR4^+/+ and QM ACKR4^−/− B_EM in drLN or B_CM in blood of ACKR4^+/+ and ACKR4^−/− hosts. Data merged from three independent experiments with 4–5 mice each. Two-tailed Mann-Whitney test. b drLN from an Cγ1-Cre mTmG mouse 8 d after immunization. Arrows: eGFP⁺ B_EM inside the SCS. Representative image of nine lymph nodes. c eGFP⁺ B_EM in the SCS of drLN in Cγ1Cre mTmG ACKR4^+/+ or ACKR4^−/− mice at d8 and d14 after foot immunization. d B_CM in distLN in ACKR4^+/+ or ACKR4^−/− mice after foot immunization. Data in c and d are merged from two independent experiments with 3–5 mice each. Two-tailed Mann-Whitney test. e Intravital observation of B_EM entry into SCS in Cγ1Cre mTmG ACKR4^+/+ or ACRK4^−/− drLN. f Quantitation of intravital eGFP⁺ B_EM in SCS of ACKR4^+/+ or ACKR4^−/− drLN. Each dot represents cell counts per field of view of a 10 μm Z stack. Pooled data from imaging of three ACKR4^+/+ and two ACKR4^−/− popliteal LNs. Two-tailed unpaired t test, ***P = 2.33 × 10⁻⁷. g Automated B cell tracking showing fraction of B_EM tracks that are inside the SCS or recycling from the SCS into the lymph node parenchyma. Images from five ACKR4^+/+ and 2 ACKR4^−/− popliteal LNs were analyzed. Each symbol corresponds to the average fraction of tracks from one video, total n of tracks = 2478. One-tailed unpaired t test, *p = 0.0268; **p = 0.0064.