Transport of marginal zone (MZ) MARCO into follicles is independent of MZ B-cell shuffling. Splenic lymphocytes from BALB/c mice were labeled with anti-CR1/2 and anti-IgM to distinguish MZ B cells (in R1 gate) from follicular B cells (in R2 gate) and immature B cells (in R3 gate), and also lymphocytes from peripheral lymph node cells, used as a staining control (A, left top and lower). Histogram overlays show the lack of MARCO (top right) and the presence of detectable complement C4 (lower right) on MZ B cells corresponding to R1 gate (filled histogram) as compared with the isotype control (empty histogram). Numbers in the representative histogram overlays indicate the ratio of mean fluorescence intensities (MFI) between the expression of MARCO or C4 and isotype control (n=5). (B-E) shows the distribution of MARCO (red) and follicular dendritic cell (FDC)-associated CR1/2 (green) in (B) Blc-/-, (C) Cxcr5-/- and (D) S1pr1TSS transgenic mutants affecting follicular migration of B cells as compared with the (E) B6 wild-type control sample. Note the absence of follicles and CR1/2high FDCs in mice deficient for BLC/CXCL13 and CXCR5. Arrows in (D) and (E) point to FDC-associated MARCO (n=2–4). Bar size in B/C, 100µm; in D/E, 20µm.