Binding of human alpha-interferons to natural killer cells

Area of Science:

• Immunology
• Molecular Biology
• Virology

Background:

• Recombinant human leukocyte interferon IFN-alpha J exhibits antiviral and antiproliferative activity on human cells.
• IFN-alpha J does not enhance natural killer (NK) cell activity, unlike other interferons like IFN-alpha A.
• IFN-alpha J can inhibit the NK-boosting effects of IFN-alpha A, indicating potential interaction with the IFN-alpha receptor on NK cells.

Purpose of the Study:

• To directly investigate the binding of IFN-alpha J to NK cells.
• To compare the receptor binding affinity of IFN-alpha J and IFN-alpha A on NK cells.
• To determine if differences in receptor binding explain the differential activity of IFN-alpha J and IFN-alpha A on NK cells.

Main Methods:

• Demonstration of IFN-alpha J binding to NK cells.
• Competition assays using [125I]IFN-alpha A to assess binding site occupancy.
• Measurement of equilibrium dissociation constants (Kd) for IFN-alpha J and IFN-alpha A on NK cells and Daudi cells.

Main Results:

• IFN-alpha J directly binds to NK cells.
• IFN-alpha J competes with [125I]IFN-alpha A for binding sites on NK cells.
• The equilibrium dissociation constant for IFN-alpha J is 20-30 times greater than for IFN-alpha A on NK cells, with similar relative Kd values observed on Daudi cells.

Conclusions:

• IFN-alpha J binds to the IFN-alpha receptor on NK cells.
• The observed differences in equilibrium binding constants between IFN-alpha J and IFN-alpha A on NK cells do not fully account for the lack of IFN-alpha J's NK-enhancing activity.
• Further investigation is needed to elucidate the mechanisms behind IFN-alpha J's inactivity on NK cells despite receptor binding.