Interferon induction in marrow-derived macrophages: regulation by L cell conditioned medium

Area of Science:

• Immunology
• Cell Biology

Background:

• Mouse bone marrow cells cultured with L cell conditioned medium (LCM) produce macrophages sensitive to interferon (IFN) induction.
• LCM contains colony stimulating factor (CSF), a key growth factor for myeloid cells.

Purpose of the Study:

• To investigate the role of LCM and its component CSF in modulating macrophage sensitivity to IFN induction by various stimuli.
• To determine if CSF affects the initial interaction of macrophages with inducers or the subsequent IFN synthesis.

Main Methods:

• Macrophage cultures were deprived of LCM for varying periods before induction with polyI:C, LPS, or NDV.
• Anti-CSF serum was added to LCM-enriched medium to assess CSF's specific role.
• LCM-deprived cultures were reincubated with conditioned medium to evaluate restoration of IFN induction.

Main Results:

• Removal of LCM significantly reduced IFN induction by polyI:C and LPS but not by NDV.
• Addition of anti-CSF serum mimicked the effect of LCM removal on polyI:C and LPS-induced IFN production.
• Re-incubation with conditioned LCM restored IFN induction by polyI:C in previously deprived cultures.

Conclusions:

• CSF in LCM is crucial for optimal IFN induction by non-viral inducers (polyI:C, LPS) in macrophages.
• CSF likely regulates the initial interaction between macrophages and these inducers, rather than IFN synthesis or secretion.
• These findings highlight CSF's role in innate immune responses mediated by macrophages.