Fig 1: B cells from aged donor mice have enhanced extrafollicular response and reduced GC formation early post-vaccination. (a) Representative flow cytometric plots of CD138+ IRF4+ plasma cells gated on donor cells from 10- or 93-week old donor mice in recipient spleens 6 days post-transfer and immunisation. Numbers adjacent to gates indicate percentage of donor HEL+ B220+ cells. Percentage and number of donor-derived CD138+ IRF4+ plasma cells are plotted on the graphs on the right. (b) Representative flow cytometric plots showing gating strategies for donor-derived GC B cells (CD38- GL7+), activated B cells (CD38+ GL7+) and memory B cells (CD38+ GL7- IgD-) from 10 weeks or 93 week old donor mice. Numbers adjacent to gates indicate percentage of donor HEL+ B220+ cells. (c) Percentage and number of HEL+ donor-derived GC B cells in recipient spleen on day 6 post-transfer and immunisation. (d) Graph showing the ratio of GC B cells: Plasma cells numbers derived from donor cells from 10 weeks or 93 weeks old donor mice. (e, f) Percentage and number of (e) CD38+ GL7+ B cells and (f) CD38+ GL7- IgD- memory B cells on day 6 post-transfer and immunisation. Bar graphs show the results of one of two independent experiments (n = 5–7 per group/experiment). Bar height corresponds to the mean, error bars indicate standard deviation, and each symbol represents one biological replicate. Statistics were calculated using the unpaired Mann–Whitney U test.