CD4⁺ T Cell-Dependent Macrophage Activation Modulates Sustained PS Exposure on Intracellular Amastigotes of...

Area of Science:

• Parasitology
• Immunology
• Cell Biology

Background:

• Leishmania amazonensis amastigotes utilize surface phosphatidylserine (PS) for macrophage infection and proliferation.
• This PS exposure, termed apoptotic mimicry, correlates with host susceptibility.
• The influence of host cellular responses on parasite PS expression remains unclear.

Purpose of the Study:

• To investigate whether host cellular responses modulate phosphatidylserine (PS) expression on intracellular Leishmania amazonensis amastigotes.
• To elucidate the role of CD4+ T cells and macrophage activation in regulating parasite PS exposure.
• To understand the mechanisms maintaining PS expression on intracellular amastigotes.

Main Methods:

• In vitro and in vivo studies assessing PS expression on amastigotes.
• Analysis of cytokine profiles (Th1/Th2) during L. amazonensis infection.
• Investigation of nitric oxide and polyamine production.
• Experiments using lymphopenic nude mice and adoptive transfer of CD4+ T cells.
• Histopathological analysis of anti-PS antibody-treated mice.

Main Results:

• Host CD4+ T cell and macrophage activation status significantly modulated PS exposure on intracellular amastigotes.
• A mixed Th1/Th2 cytokine profile optimized macrophage stimulation, favoring PS exposure.
• Sustained low levels of nitric oxide and polyamine production were essential for maintaining parasite PS.
• Amastigotes from nude mice lacked surface PS; CD4+ T cell transfer restored it.
• Anti-PS antibody treatment exacerbated inflammation and mimicked nude mouse lesions.

Conclusions:

• Pathogenic CD4+ T cells are crucial for Leishmania amazonensis disease progression.
• Parasite phosphatidylserine (PS) is a key strategy for subverting host immune responses.
• Host immune status critically regulates parasite PS expression, impacting infection dynamics.