CD90 is not constitutively expressed in functional innate lymphoid cells.

Area of Science:

• Immunology
• Cell Biology
• Gastroenterology

Background:

• Innate lymphoid cells (ILCs) are crucial immune cells in mucosal tissues.
• T cell biology concepts, including flow cytometry markers like CD90, have been applied to ILC identification.
• CD90 expression was generally expected on functional ILCs.

Purpose of the Study:

• To investigate the expression patterns of CD90 on intestinal ILCs.
• To characterize the functional significance of CD90-negative ILC subsets.
• To determine the role of CD90-low/negative ILCs in gut inflammation.

Main Methods:

• Flow cytometry analysis of intestinal ILC populations.
• In vitro stimulation assays to assess ILC responses.
• In vivo studies using mouse models of gut dysbiosis and colitis.

Main Results:

• A sub-population of intestinal ILCs exhibits low or absent CD90 expression, contrary to expectations.
• CD90-negative and CD90-low CD127+ ILCs are present across all ILC subsets in the gut.
• The frequency of these ILCs is influenced by in vitro stimuli and in vivo dysbiosis.
• These ILCs are a source of IL-13, IFNγ, and IL-17A during homeostasis and colitis.

Conclusions:

• CD90 is not a universally or constitutively expressed marker on all functional intestinal ILCs.
• CD90-negative ILCs represent a distinct functional subset with implications for gut immunity.
• Understanding ILC heterogeneity is critical for deciphering immune responses in the gut.