Thursday, July 14, 2016

Hybrid NKB cells are source of early IL-18

By screening for NK1.1+ cell population in different tissues, the authors noticed that spleen and mLNs [but not other tissues] contained cell population expressing CD19 and IgM, a canonical B cell markers.

Image flow analysis confirmed that both NK1.1 and CD19 markers were expressed by the same cells.

This new NKB cell population were absent in RAG-KO, IL-2RgcKO, B cell or NK-deficient mice, suggesting unique lineage (its precursors appear to express CD122, IL-2Rbeta chain).

In vitro functional analysis showed that NKB cells were innate producers of IL-18 and IL-12 (IL-12p40, most likely). Of note, NKB cells did not secrete antibody after stimulation.

In an in vivo infection model NKB cell-deficient mice (created by reconstituting lethally irradiated mice with Id2 and mMT deficient bone marrow cells) showed high susceptibility to L.M. infection.

Finally, the authors showed that IL-18 produced by wt NKB cells played important role in disease resistance against L.M. infection.

In summary, this study identified new type of innate cells expressing NK and B cell markers, called NKB cells, that were involved in early IL-18 production that contributed early waves of IFN-gamma from NK and ILC1 cells and resistance to L.M. infection. It is not clear what roles surface CD19 or IgM play in NKB cell functionality.

David Usharauli

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