Uncovering Leishmania-macrophage interplay using imaging flow cytometry

Area of Science:

• Immunology
• Cell Biology
• Parasitology

Background:

• Host-pathogen interactions are crucial, with intracellular parasites like Leishmania infecting phagocytes.
• Macrophages are key immune cells activated by cytokines (e.g., IFN-γ) and Toll-like receptor (TLR) agonists.
• Leishmania parasites evade macrophage defenses by interfering with critical intracellular signaling pathways.

Purpose of the Study:

• To investigate the impact of Leishmania donovani infection on macrophage signaling pathways.
• To evaluate parasitic load within macrophages using advanced imaging techniques.
• To explore the potential immunosuppressive effects of infected macrophages on bystander cells.

Main Methods:

• Utilized transgenic Leishmania donovani expressing DsRed2 for parasite tracking.
• Employed imaging-flow cytometry to quantify parasitic loads within macrophages in vitro.
• Assessed Nuclear Factor kappa B (NFκB) translocation in infected and bystander macrophages.

Main Results:

• Quantified parasitic loads in Leishmania-infected macrophages.
• Demonstrated impaired NFκB translocation to the nucleus in infected macrophages.
• Observed similar NFκB translocation impairment in uninfected bystander macrophages upon TLR4 agonist stimulation.

Conclusions:

• Leishmania donovani infection impairs macrophage microbicidal function by disrupting IFN-γ and TLR signaling.
• Infected macrophages may exert immunosuppressive effects on uninfected bystander cells.
• This suggests a novel mechanism of immune evasion and regulation in Leishmania infections.