Endotoxin-induced serum factor that stimulates gamma interferon production

Area of Science:

• Immunology
• Molecular Biology
• Cellular Biology

Background:

• Mycobacterium bovis BCG infection and lipopolysaccharide (LPS) challenge in mice.
• Interferon-gamma (IFN-gamma) is a critical cytokine in immune responses.
• Interleukin-2 (IL-2) plays a key role in lymphocyte activation.

Purpose of the Study:

• To investigate the mechanism of IFN-gamma induction in mice post-LPS challenge.
• To identify the factor responsible for enhanced IFN-gamma production.
• To understand the genetic control of IFN-gamma production.

Main Methods:

• Serum transfer assays from BCG-infected and LPS-challenged mice to normal mice.
• In vitro culture of normal mouse spleen cells with serum and IL-2.
• Inhibition studies using anti-IL-2 receptor antibody.
• Gel filtration to estimate molecular weight of the active substance.
• Comparison of IFN-gamma production across different mouse strains.

Main Results:

• Serum from BCG-infected, LPS-challenged mice induced significant IFN-gamma in normal spleen cell cultures.
• The inducing activity was present within 90 minutes post-challenge and required IL-2.
• The active substance had an estimated molecular weight of 70,000.
• Strain-specific differences in serum activity correlated with in vivo IFN-gamma levels, but not with lymphocyte response to the factor.
• The factor induced IFN-gamma in macrophage-depleted splenocytes.

Conclusions:

• An unidentified factor in serum cooperates with IL-2 to induce IFN-gamma in splenocytes.
• IFN-gamma production in vivo is likely regulated at the level of this unknown factor's synthesis.
• Genetic control of IFN-gamma production resides in the synthesis of this factor, not lymphocyte responsiveness.