Figure 3. Similar phenotype of B cells in lymph node and lung tissue.

Flow cytometric analysis (day 17) of antigen-specific (CD45.1⁺) B cells from lung-draining lymph nodes and lung tissue. (a) Comparison of plasma cells, defined as CD19^low CD138⁺, from lymph nodes and lungs. Shown are flow cytometric plots, and the frequency and absolute numbers of NP-specific B cells with a plasma cell phenotype from a representative experiment and the ratio of plasma cells in lung-draining lymph nodes as pooled data from 3 experiments with 20 animals total. (b) Comparison of GC/GC-like B cells from lymph nodes (Ln) and lung tissue. Frequency and absolute numbers from a representative experiment, and relative distribution of GL7⁺ PNA⁺ B cells between lymph node and lung as pooled data from 4 experiments with 26 animals. For further characterization, cells were co-stained for CD38 and intracellular Bcl-6 or activation-induced cytidine deaminase (AID). CD38 expression is shown as histograms on GL7/Bcl-6 double-negative (black) versus double-positive (orange) cells. AID expression is shown on GL7/PNA-positive (red line) and -negative (black line) cells relative to an isotype control (filled grey histogram; concatenated flow cytometry data from five animals). (c) Staining of lung tissue containing ectopic lymphoid tissue defined by the presence of FDC (CD21/35⁺, yellow) and a greater number of unstructured infiltrates. Staining with the GC B-cell marker GL7 is shown in magenta. (d) Co-staining of transgenic B cells (magenta) and the cell proliferation marker Ki-67 (yellow) in an FDC-negative infiltrate. Scale bars, 100 μm, original magnification × 20. Data are representative for at least two independent experiments. Error bars show s.e.m. NS, not significant: P≥0.05, *P<0.05, **P<0.01 by Mann–Witney U-test.