Natural killer cells in experimental and human leishmaniasis

Area of Science:

• Immunology
• Parasitology
• Cell Biology

Background:

• Leishmania parasites trigger rapid but temporary activation of natural killer (NK) cells.
• NK cell activation in mice involves toll-like receptor 9-dependent dendritic cell stimulation and IL-12 production.
• While not essential for ultimate parasite control, NK cells are a key source of interferon-gamma (IFN-γ), crucial for antileishmanial macrophage activity and T helper cell responses.

Purpose of the Study:

• To provide an integrated overview of NK cell behavior in experimental and human leishmaniasis.
• To explore the migration, activation, inhibition, and function of NK cells during Leishmania infections.
• To discuss the potential therapeutic modulation of NK cells for treating leishmaniasis.

Main Methods:

• Review of existing literature on NK cell responses in Leishmania infections.
• Analysis of studies detailing NK cell activation pathways, including TLR9 and IL-12.
• Examination of evidence for NK cell involvement in both cutaneous and visceral leishmaniasis (VL).

Main Results:

• NK cells are transiently activated by Leishmania, producing IFN-γ that enhances macrophage antileishmanial activity.
• NK cell cytotoxic functions are largely dispensable as infected myeloid cells resist lysis.
• Evidence in human leishmaniasis suggests NK cell modulation, with suppressed activity in chronic infections and recovery post-treatment.

Conclusions:

• NK cells play a complex, multifaceted role in leishmaniasis, primarily through IFN-γ production rather than cytotoxicity.
• Understanding NK cell dynamics offers potential for novel therapeutic strategies targeting leishmaniasis.
• Further research into NK cell migration, activation, and inhibition is warranted for effective leishmaniasis treatment.