Figure 7. Evolving functionalities of aging antiviral CD8⁺ T_M: granzymes, degranulation, and CTL activity.

(A) Temporal regulation of granzyme mRNA (p14⁺ T_E/M, microarray data) and protein (D^bNP₃₉₆⁺CD8⁺ T_E/M) expression analyzed directly ex vivo. (B) Lamp1, -2, and -3 mRNA expression and degranulation capacity of aging p14⁺ T_E/M and NP₃₉₆-specific CD8⁺ T_M, respectively. (C) Left, young (Y) and old (O) LCMV-immune mice harboring identical numbers of blood-borne CD8⁺ T_M were used to assess CD8⁺ T_M CTL activities in vivo; middle, killing kinetics determined in blood after AT of 4.5 × 10⁶ differentially CFSE-labeled control and NP₃₉₆ peptide–coated target cells each (histograms gated on target cells retrieved 5 hours after AT into LCMV-immune [young, gray; old, black] or naive [open] mice); right, splenic D^bNP₃₉₆⁺CD8⁺ T_M numbers at conclusion of assay and extent of specific killing. (D) D^bNP₃₉₆⁺CD8⁺ T_M abundance and killing activity in spleen after AT of 4.5 × 10⁵ purified young or old D^bNP₃₉₆⁺CD8⁺ T_M into naive recipients followed by transfer of 4.5 × 10⁵ sensitized and control target cells each; data generated with n ≥ 3 mice/group in multiple independent experiments. *P < 0.05, **P < 0.01, and ***P < 0.001 by 1-way ANOVA or Student’s t test. PBMC, peripheral blood mononuclear cells.