Decreased IL-2, IFN-γ, and IL-10 production by aged mice during the acute phase of E55+ retrovirus infection

We previously reported that aged mice demonstrated a 12-week delay in virus clearance compared to young mice after infection with E55+ murine leukemia retrovirus (E55+MuLV). The current study demonstrates that both the levels of IL-2, IFN-γ, and IL-10 and the number of cells producing IL-2 and IFN-γ were lower at 2 and 4 weeks postinfection (p.i.) in aged compared to young mice after virus-specific stimulation of spleen cells in vitro. In both age groups, IL-2 and IL-10 were produced by CD4⁺ T and B cells, respectively. IFN-γ was produced mainly by CD4⁺ T cells at 2 weeks p.i. and by CD4⁺ and CD8⁺ T cells at 4 weeks p.i. in young, but primarily by CD8⁺ T cells, in aged mice. Therefore, delayed virus clearance is associated with age-related decreases in type 1 and type 2 cytokines and a shift in the primary source of at least one cytokine.