Relationship between colony-stimulating activity and interferon production during infection

Area of Science:

• Immunology
• Hematopoiesis
• Microbial Pathogenesis

Background:

• Spleen cells normally produce colony-stimulating factors (CSF) that support hematopoietic progenitor cell growth.
• Listeria monocytogenes infection significantly alters immune responses within the spleen.

Purpose of the Study:

• To investigate the effect of Listeria monocytogenes infection on CSF production by mouse spleen cells.
• To identify the mechanisms underlying the suppression of CSF activity post-infection.

Main Methods:

• In vitro culture of normal mouse spleen cells with heat-killed Listeria monocytogenes.
• Co-culture experiments using T-cell enriched spleen cells from infected mice with normal spleen cells.
• Measurement of colony-stimulating activity (CSA) in culture supernatants.
• Neutralization of interferon-gamma (IFN-gamma) using specific antibodies.

Main Results:

• Normal spleen cells produced CSF, supporting bone marrow cell proliferation.
• Spleen cells from Listeria-infected mice showed suppressed CSA from Day 3 to Day 17 post-infection.
• T-cell enriched spleen cells from infected mice suppressed CSA production in normal spleen cells.
• Suppression of CSA correlated with IFN-gamma production; antibody neutralization restored CSA.
• An early, IFN-gamma-independent decrease in CSA was observed 2-3 days post-infection.

Conclusions:

• Listeria monocytogenes infection leads to a T-cell mediated suppression of CSF production in mouse spleen.
• Interferon-gamma plays a significant role in this suppression, although an early independent mechanism also exists.
• These findings highlight a complex interplay between infection, immune cells, and hematopoietic regulation.