LIR‐1 educates expanded human NK cells and defines a unique antitumor NK cell subset with potent antibody‐dependent cellular cytotoxicity

Abstract

Objective. KIR and NKG2A receptors educate human NK cells to stay responsive to cells with diminished HLA class I. Here, we addressed whether the HLA class I-binding receptor LIR-1 (LILRB1/ ILT2/CD85j), which is widely expressed on human NK cells, can mediate education and contribute to antitumor functions of NK cells. Methods. Healthy donor NK cells either unstimulated, overnight cytokine-activated or ex vivo-expanded were used to target human cell lines. Phenotype and function were analysed using flow cytometry and 51 Cr-release assays. Results. We found that the inhibitory receptor LIR-1 can mediate NK cell education under specific conditions. This novel finding was exclusive to expanded NK cells and further characterisation of the cells revealed high expression of granzyme B and DNAM-1, which both previously have been linked to NK cell education. Corroborating the rheostat education model, LIR-1 co-expression with an educating KIR further increased the responsiveness of expanded NK cells. Inversely, antibody masking of LIR-1 decreased the responsiveness. LIR-1 + expanded NK cells displayed high intrinsic ADCC that, in contrast to KIR and NKG2A, was not inhibited by HLA class I. Conclusion. These findings identify a unique NK cell subset attractive for adoptive cell therapy to treat cancer. Given that LIR-1 binds most HLA class I molecules, this subset may be explored in both autologous and allogeneic settings to innately reject HLA class Itumor cells as well as HLA class I + target cells when combined with antitumor antibodies. Further studies are warranted to address the potential of this subset in vivo.

Expanded NK cells used for adoptive cell therapy maintain diverse clonality and contain long-lived memory-like NK cell populations

“… 50 In prior flow cytometry studies, proportions of human NK cells expressing KIR tended to decrease during expansion with irradiated LCL feeders. 51 Highly biased expression of KIR in barcoded macaque clones provides compelling evidence for origin of those clones from single NK cells expressing or lacking KIR, followed by expansion in vivo while retaining KIR status, then continued contribution in vitro of these clones to the NK cell product generated. Consistent with this theory, contributions of different animals’ highly KIR3DL01 biased (positive plus negative) clones to the repertoire ( Figure 5 ) mirrored the contributions of in vivo expanded NK clones categorized independently in Figure 4 .…”

Polygenic risk score analysis identifies deleterious protein-coding variants in novel immune pathway genesATP8B4, FCGR1A, andLILRB1that associate with Alzheimer’s disease

“…It is expressed on immune cells where it is known to bind to MHC class I molecules on antigen presenting cells and transduces a negative signal though immunoreceptor tyrosine-based inhibition motif (ITIM) that suppresses immune responses [56, 57]. LILRB1 on natural killer cells may also have a prominent role in inflammation following an immune response [58]. The stop-gain variant in LILRB1 , which strongly decreases risk of AD, will likely impair the effect of ligands that modulate the immune system by binding to LILRB1 .…”

Perspectives of targeting LILRB1 in innate and adaptive immune checkpoint therapy of cancer

“…In particular, LILRB1 is expressed by terminally differentiated NK cells expressing CD57 and numerous KIR and by virus-induced adaptive NK cells ( 85 – 88 ). Recent findings show that at least under certain conditions LILRB1 contributes to NK cell education - a process that counterbalances the responsiveness of individual NK cells with their sensitivity for inhibition by cognate HLA class I molecules ( 89 , 90 ). Importantly, LILRB1 engagement by HLA-G impairs the formation of the NK cell activating synapse by inhibiting the polarization of lytic granules and the microtubule organizing centre and impaired filamentous actin accumulation ( 91 ).…”