Circulating HLA-DR(+) natural killer cells have potent lytic ability and weak antigen-presenting cell function

Area of Science:

• Immunology
• Cell Biology

Background:

• The dual functionality of immune cells, specifically possessing both natural killing and antigen-presenting capabilities, has been a subject of recent debate in murine models.
• Investigating such dual-function cells in humans is crucial for understanding immune system complexity.

Purpose of the Study:

• To identify and characterize human immune cells that co-express markers for antigen-presenting cells (APCs) and natural killer (NK) cell receptors.
• To determine if these cells exhibit combined cytotoxic and antigen-presenting functions.

Main Methods:

• Analysis of mononuclear cells from human blood, spleen, liver, and lymph nodes.
• Flow cytometry to identify cell populations co-expressing HLA-DR (APC marker) and CD56 (NK cell receptor).
• Functional assays to assess killing capacity and antigen-presenting capabilities.

Main Results:

• Two distinct populations of CD56+ cells co-expressing HLA-DR were identified in human tissues.
• A subset of CD56+ cells with high HLA-DR expression resembled conventional dendritic cells (DCs).
• A separate population of CD56+ cells with low HLA-DR expression demonstrated potent NK cell killing activity alongside weaker APC function.

Conclusions:

• Human blood and lymphoid tissues harbor distinct CD56+ cell populations with dual NK and APC characteristics.
• These findings reveal a novel immune cell subset with potential implications for immune response and regulation.