Fig 1: Impaired B cell responses after ChAdOx1 nCoV-19 immunization of aged mice(A and B) B cell response in 3-month-old (3mo) or 22-month-old (22mo) mice 9 days after immunization with ChAdOx1 nCoV-19 or PBS. Flow cytometric evaluation of the percentage (A) and number (B) of plasma cells in the iliac lymph node.(C) Pie charts showing the proportion of IgM+IgD– (orange) and switched IgM–IgD– (blue) plasma cells from (A) and (B).(D and E) Serum IgM (D) and IgG (E) anti-spike antibodies 9 days after immunization.(F) Pie charts showing the proportion of anti-spike IgG of the indicated subclasses in the serum 9 days after immunization.(G and H) Percentage (G) and number (H) of germinal center B cells in the iliac lymph node.(I) Pie charts showing the proportion of IgM+IgD– (orange) and switched IgM–IgD– (blue) germinal center cells from (G) and (H).(J–M) Number of T follicular helper (J) and T follicular regulatory (K) cells in the draining lymph node. Confocal images of the spleen of ChAdOx1 nCoV-19-immunized mice of the indicated ages; in (L), the scale bars represent 500 µm; in (M), the scale bars represent 50 µm. IgD+ B cell follicle are in green, CD3+ T cells in magenta, Ki67+ cells in blue, and CD35+ follicular dendritic cells in white.(N and O) Percentage (N) and number (O) of splenic germinal center B cells.(P) Percentage of Ki67+ B cells in the spleen.(Q and R) Number of splenic T follicular helper (Q) and T follicular regulatory (R) cells.Serum IgM (S) and IgG (T) anti-spike antibodies and IgG subclasses (U) 28 days after immunization. For all bar graphs, the bar height corresponds to the median and each circle represents one biological replicate. The Shapiro-Wilk normality test was used to determine whether the data are consistent with a normal distribution, followed by either an ordinary one-way ANOVA test for data with a normal distribution or a Kruskal-Wallis test for non-normally distributed data alongside a multiple comparisons test, for ELISA data analyses were done on log transformed values. Data are representative of two independent experiments (n = 4–8 per group/experiment).