Figure 2.

wt^∗ Mice Have Lymphocyte Defects that Mirror Immunosenescence

(A and B) Absolute B cell lymphopenia in the spleen (A) is associated with low serum IgM levels (B).

(C) Fold increase over baseline in antigen-specific IgM 1 wk after immunization. Baseline IgM levels were measured in each mouse 3 days prior to injection.

(D and E) Absolute T cell lymphopenia in splenocytes is skewed and favors loss of CD4 cells (D), as shown by the decrease in CD4/CD8 ratio (E).

(F–J) T cells from wt^∗ and mTR^+/− mice with short telomeres fail to expand after CD3-CD28 stimulation, as quantitated by the MTT assay (F). This failure to expand is associated with an increase in the proportion of Annexin-V-positive apoptotic cells (G), as well as a decrease in the proportion of live cells in S-phase (I). Representative flow cytometry plots for the quantitation shown in (G) and (I) are show in (H) and (J), respectively. Mice were examined at 3–6 mo of age.