Suppression of interleukin 2 activity by natural products: effects of serum lipoproteins.

The results presented here demonstrate that mouse serum lipoproteins inhibit Interleukin 2 (IL2)-mediated proliferation of CTLL-2 cells. Lipoproteins account for a variable portion (29-83%) of the total inhibitory activity of whole serum and are not specific inhibitors of IL2-mediated cell proliferation, as evidenced by their inhibitory activity for non-IL2-dependent MPC 11 cells. Lipoproteins did not accelerate the death of CTLL-2 cells deprived of IL2, indicating that their inhibition of proliferation is not due to toxic effects. Finally, the inhibitory activity of serum and isolated lipoproteins was increased when the donor mice were maintained on a diet high in polyunsaturated fats for 16 days prior to bleeding. These findings provide a basis for future investigations of the relationship between dietary fats, lipoprotein quantity and composition, and alteration of immune responses.