Dietary conjugated linoleic acid influences the immune response of young and old C57BL/6NCrlBR mice

Aging is associated with a decline in the immune response in mammals. Conju gated linoleic acid (CLA) has been suggested to have immunoenhancing proper ties. We examined the influence of dietary CLA on the immune response of yo ung and old mice. Forty young (4 mo) and 40 old (22 mo) mice consumed ad li bitum diets containing 0 or 1 g CLA /100 g for 8 wk. Splenocytes from half of the mice were isolated to evaluate proliferation to concanavalin A (Con A) (0.5, 1.5, 5.0 mg/L) and phytohemagglutinin A (PHA) (5, 20, 40 mg/L) and lipopolysaccharide (LPS) (5, 15, 30 mg/L), natural killer cell (NK) activi ty and prostaglandin (PG)E-2 and interleukin (IL)-2 production. The remaini ng mice were used to evaluate in vivo delayed-type hypersensitivity (DTH) s kin response. There was a significant decline due to age in response to all three mitogens tested (P < 0.05). CLA supplementation significantly increa sed all CLA isomers measured in hepatic neutral lipids and phospholipids (P < 0.05). Young mice fed 1% CLA had greater splenocyte proliferation in res ponse to Con A (0.5 and 5.0 mg/L) and PHA (40 mg/L) (P < 0.05) than young m ice fed control diet. Old mice fed 1 g CLA/100 g had significantly higher p roliferative response to optimal concentrations of Con A (1.5 mg/L) (P < 0. 001) than the mice fed the control diet. Old mice fed the control diet had significantly lower splenocyte IL-2 production than the young mice (P < 0.0 05). CLA-supplemented young mice had significantly higher splenocyte IL-2 p roduction than those fed the control diet (P < 0.05). CLA had no effect on NK cell activity, PGE(2) production or DTH in young or old mice. Further st udies ave needed to determine the mechanism of CLA-induced enhancement of I L-2 production and T cell proliferation.