Identification of a human non-interferon lymphokine activating monocyte complement biosynthesis

Area of Science:

• Immunology
• Molecular Biology
• Biochemistry

Background:

• Mononuclear cells produce activities that stimulate monocytes.
• Complement system proteins (C1, C2, C3) are crucial for immune responses.
• Lymphokines are key mediators in immune cell communication.

Purpose of the Study:

• To define and purify a monocyte-stimulating lymphokine.
• To characterize the biochemical properties of this novel lymphokine.
• To investigate the mechanism by which this lymphokine enhances complement synthesis.

Main Methods:

• Purification of lymphokine from activated peripheral blood mononuclear cells using ammonium sulfate precipitation, phenyl-Sepharose chromatography, and electrofocusing.
• Biochemical characterization including isoelectric point (pI) and molecular weight (Mr) determination via SDS-PAGE.
• Amino acid analysis to determine the molecule's composition.
• Analysis of complement biosynthesis enhancement at a pretranslational level.

Main Results:

• A lymphokine was purified with monocyte-stimulating activity, enhancing synthesis of complement C1 subcomponents, C2, and C3.
• The purified lymphokine has a pI of 7.9 and Mr of 14,600 (with oligomeric forms at 27,000 and 56,000).
• Amino acid analysis showed high hydrophobicity (34%) and absence of histidine, suggesting novelty.
• The lymphokine enhances C1r and C1s biosynthesis at a pretranslational level, distinct from gamma-interferon.

Conclusions:

• A novel monocyte-activating lymphokine has been identified and purified.
• This lymphokine plays a role in regulating complement biosynthesis.
• Its unique characteristics differentiate it from known immune mediators like gamma-interferon.