Circulating innate lymphoid cells (cILCs): Unconventional lymphocytes with hidden talents

Area of Science:

• Immunology
• Cell Biology

Background:

• Innate lymphoid cells (ILCs) are lymphocytes lacking antigen-specific receptors, primarily residing in tissues.
• ILC subtypes (ILC1, 2, 3) parallel T-cell functions.
• While tissue ILCs (tILCs) are abundant, circulating ILCs (cILCs) are increasingly studied for clinical relevance.

Purpose of the Study:

• To compare the phenotype and function of circulating ILCs (cILCs) with tissue ILCs (tILCs).
• To explore the distinct roles and potential clinical applications of cILC subtypes.
• To highlight the prognostic value of specific cILC subsets in various diseases.

Main Methods:

• Comparative analysis of cILC and tILC phenotypes and functions.
• Review of transcriptomic signatures and frequency dynamics of ILC subsets.
• Examination of clinical data linking cILCs to disease states.

Main Results:

• Circulating ILCs (cILCs) exhibit distinct functionalities compared to their tissue counterparts (tILCs).
• Circulating ILC2s are key drivers of allergic reactions, notably asthma.
• Circulating ILC1s and ILC3s are immature, acting as progenitors for NK cells and ILCs, respectively.

Conclusions:

• cILCs possess unique characteristics and functions separate from tILCs.
• The NKp44+ ILC3 subset in peripheral blood shows promise as a prognostic marker for inflammatory bowel disease and leukemia.
• Understanding cILC heterogeneity is crucial for their clinical application in disease diagnosis and prognosis.