Natural killer activity enhancing substance in normal human serum.

Area of Science:

• Immunology
• Biochemistry

Background:

• Natural killer (NK) cells are crucial for innate immunity.
• The role of normal human serum in modulating NK cell activity is not fully understood.

Purpose of the Study:

• To investigate the effect of normal human serum on NK cell activity.
• To identify the specific component within serum responsible for enhancing NK activity.

Main Methods:

• NK cell activity assays using peripheral lymphocytes.
• Serum fractionation using Sephadex G-200 and Cibacron Blue-Sepharose chromatography.
• Testing purified albumin, transferrin, PDGF, and plasminogen for NK-enhancing effects.

Main Results:

• Both fresh and heat-inactivated serum significantly enhanced NK activity in a dose-dependent manner.
• The enhancing factor was localized to fraction III after Sephadex G-200 fractionation.
• Albumin-rich subfractions and commercial human albumin demonstrated NK-enhancing activity, while other proteins did not.

Conclusions:

• Serum albumin is identified as the primary component in normal human serum that enhances NK cell activity.
• This finding suggests a previously unrecognized role for albumin in immune responses.