. 2019 Oct 13;20(20):5080. doi: 10.3390/ijms20205080

Table 1.

Summary of described NK cell subsets. The upper four rows report NK cell subsets are identified among circulating NK cells. Rows filled in grey depict NK subsets recognized within the liver.

NK Cell Subset	Phenotypic Characteristics	Functional Activity	Comments
CD56^bright NK circulating cells	CD56^bright CD16^neg/low	High cytokine production Low cytolytic activity	Considered as precursors of the more mature CD56 ^dim NK cells [13]
CD56^dim NK circulating cells	CD56^dim CD16^bright	Cytolytic activity Low cytokine production	Main circulating NK subset Terminally differentiated NK cells [13]
CD56^dim NK circulating cells	CD56^dim CD16^neg	High cytolytic activity High cytokine production in healthy individuals	Not fully functional in malignancies [17,18]
CD56^neg NK circulating cells	CD56^neg CD16^bright	Low cytolytic activity Low cytokine production	Minor subset in healthy donors Significantly expanded in chronic HIV and HCV chronic infections [19] and in CMV/EBV co-infected older healthy donors [20]
Hepatic conventional NK cells	CD56^dim CD16^bright CCR5^neg CXCR6^neg	High cytolytic activity [21]	Similar to peripheral CD56^dim [22] Promote T cell function [21]
Liver-resident NK cells	CD56^bright CD16^low CD69⁺ Tbet^low Eomes^hiCCR5⁺ CXCR6⁺	low levels of perforin and granzyme B Low cytokine production Low cytolytic activity [23]	Regulatory role through the PD1/PD-L1 signaling [21] Can acquire memory to haptens and viral antigens [24,25]