Effects of dietary conjugated linoleic acid isomers on several functional properties of macrophages and heterophils in laying hens.

1. Effects of dietary conjugated linoleic acid (CIA) on various functional properties of macrophages and heterophils in the laying hen were determined. 2. Seventy two 28-week-old-ISA brown hens were randomly assigned to one of two experimental groups and were fed diets containing 0 or 1% CLA for a total period of 18 weeks. Blood samples were collected from 6 hens per diet group every 3 weeks and macrophages and heterophils were isolated. The following variables were determined in resting and phorbol myristate acetate-activated (65 mum) macrophages and heterophils: total cell-associated urokinase plasminogen activator (u-PA), membrane-bound u-PA, free u-PA binding sites and superoxide production. 3. There were no significant differences between diet groups throughout the whole experimental period in total cell-associated u-PA, membrane-bound u-PA, free u-PA binding sites and superoxide production by resting macrophages and heterophils. 4. Activated heterophils and macrophages isolated from hens fed the CLA-supplemented diet had higher membrane-bound u-PA activity compared with the corresponding values for activated heterophils and macrophages obtained from hens fed the basal diet. These differences were significant for heterophils during weeks 6, 12, 15 and 18 and for macrophages during weeks 6, 9 and 12 of the experiment. 5. Macrophages and heterophils from hens fed the CIA diet had lower superoxide production compared with the corresponding cells from the control hens on weeks 12, 15 and 18 of the experiment. 6. Dietary CIA modulated certain aspects of the immune system in the laying hen. The increased quantity of u-PA on the membrane of macrophages and heterophils isolated from hens fed the CLA diet may facilitate the ability of these cells to reach the point of a potential inflammation (pro-inflammatory effect). 7. In contrast to the effect on the u-PA system, dietary CLA reduced superoxide production by activated macrophages and heterophils during the second half (last 9 weeks) of the experimental period suggesting that CIA may exert an anti-inflammatory effect in the laying hen.