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Front Immunol. 2012 Apr 9;3:72. doi: 10.3389/fimmu.2012.00072. eCollection 2012.

Functional Differences between Human NKp44(-) and NKp44(+) RORC(+) Innate Lymphoid Cells.

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Department of Hematology, Erasmus University Medical Center Rotterdam, Netherlands.


Human RORC(+) lymphoid tissue inducer cells are part of a rapidly expanding family of innate lymphoid cells (ILC) that participate in innate and adaptive immune responses as well as in lymphoid tissue (re) modeling. The assessment of a potential role for innate lymphocyte-derived cytokines in human homeostasis and disease is hampered by a poor characterization of RORC(+) innate cell subsets and a lack of knowledge on the distribution of these cells in adults. Here we show that functionally distinct subsets of human RORC(+) innate lymphoid cells are enriched for secretion of IL-17a or IL-22. Both subsets have an activated phenotype and can be distinguished based on the presence or absence of the natural cytotoxicity receptor NKp44. NKp44(+) IL-22 producing cells are present in tonsils while NKp44(-) IL-17a producing cells are present in fetal developing lymph nodes. Development of human intestinal NKp44(+) ILC is a programmed event that is independent of bacterial colonization and these cells colonize the fetal intestine during the first trimester. In the adult intestine, NKp44(+) ILC are the main ILC subset producing IL-22. NKp44(-) ILC remain present throughout adulthood in peripheral non-inflamed lymph nodes as resting, non-cytokine producing cells. However, upon stimulation lymph node ILC can swiftly initiate cytokine transcription suggesting that secondary human lymphoid organs may function as a reservoir for innate lymphoid cells capable of participating in inflammatory responses.


IL-17a; IL-22; RORC; fetal; human; innate lymphoid cells; lymph node; tonsil

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