Effect of Aging on Cytokine Production in Normal and Experimental Systemic Lupus Erythematosus-Afflicted Mice

Aging mice of strains susceptible to the induction of experimental systemic lupus erythematosus (SLE) develop a milder disease than young animals. To find out whether the decrease in susceptibility to disease is due to age-associated changes in cytokine profile, we first examined the secretion of cytokines by healthy mice aged 2–15 months. A gradual age-related decline in the levels of interleukin (IL)-2 and interferon (IFN) γ, and an increase in IL-4, IL-10, IL-1, and tumor necrosis factor (TNF) α were observed. Experimental SLE was induced in 2- and 10-month-old mice by immunization with the monoclonal anti-DNA antibody bearing the 16/6 Id. Early increased production of pro-inflammatory cytokines (TNFα and IL-1), followed by a peak of the Th1-type cytokines (IL-2, IFNγ) were observed in young mice. The Th2-type cytokines (IL-4, IL-10) peaked later. In contrast, only a mild increase in all of the above cytokines was determined in 10-month immunized mice. It thus appears that the decline in susceptibility to SLE induction in older mice may be related to changes in the capacity to produce cytokines.