D6^active B1 cells in omentum, blood, spleen, mesenteric lymph node, and Peyer patches. (A) Overlaid CCL2^AF647 uptake profiles for WT (black) and D6-deficient (KO, gray) omental CD19⁺ B-cell subsets (identified using Abs against CD5, CD11b, and CD23 as in the analysis of peritoneal cavity lavage cells). Numbers above plots show proportion of retrieved CD19⁺ cells in each subset in WT mice (means ± SEM). B1d cells (CD19⁺CD11b⁻CD5⁻CD23⁻D6^active) are indicated in the far right plot. (B) Contour plot showing CD11b expression on CD19⁺ blood cells with the proportion of CD19⁺ CD11b⁺ cells indicated. Overlaid CCL2^AF647 uptake profiles are shown in the right panels (WT, black; D6-deficient (KO), gray). (C) Contour plots showing gating of CD19⁺ splenocytes for FO/T2 cells, MZ B cells, and B1 cells fractionated into CD21⁺ (B1²¹⁺) and CD21⁻ (B1²¹⁻) subsets. Events in gate R1 (CD5^hi) are rare T/B-cell conjugates and were excluded. The CD19⁺IgM^hiCD23^loCD5⁻CD21⁻ population, containing T1 progenitors, are labeled ‘21⁻'. The overlaid histograms show CCL2^AF647 uptake profiles for WT (black) and D6-deficient (KO; gray) subsets. (D-E) CD19⁺ cells in mesenteric lymph node and pooled Peyer patches fractionated into CD23^lo, CD23^med, and CD23^hi subsets (central dot plot in each figure). Subset size, as a proportion of retrieved WT CD19⁺ cells, is indicated above each CCL2^AF647 uptake dot plot. The mean ± SEM of CCL2^AF647-positive cells (as a proportion of retrieved CD19⁺ cells) is indicated on each plot. All data are representative of experiments repeated 2-5 times.