Influence of acute-phase proteins on the activity of natural killer cells

Abstract

The effects ofα ₁-antitrypsin (α ₁,-AT),α ₁,-acid glycoprotein (α ₁AGP), and haptoglobin (Hp), the main constituents ofα-globulin and which belong to acute phase proteins, on NK activity were examined using K562 cells as the NK target cells. Among the three proteins,α ₁,-AT andα ₁AGP had inhibitory effects on NK activity for “fast target” K562 cells. Theα,-AT preparations having the same protein concentration and a different trypsin inhibitory capacity (TIC) had an equal effect. Althoughα ₁AT andα ₁,-AGP equally reduced the NK activity, the mechanism involved in the reduction differed, in that the effect ofα ₁,-AT directed toward NK cells reduced their binding capacity with the target cells,α ₁,-AGP probably interacts with a cytotoxic factor secreted from NK cells following effector-target interaction. These studies suggest that each of the acute-phase proteins, which increase following inflammation, inhibits NK cell function by two distinct mechanisms.