Distinct indirect pathways govern human NK-cell activation by TLR-7 and TLR-8 agonists.
NK cells limit the emergence of cancers and viral infections by surveillance of 'missing-self' and 'induced-self' ligands, and by direct recognition of pathogen-associated molecules. We examined individual roles for Toll-like receptors (TLRs)-7 and -8 in human NK-cell activation using synthetic, small molecule agonists of either TLR-7 (imiquimod and 3M-001), TLR-8 (3M-002) or both TLR-7/8 (3M-003 and R-848) for comparison with known ligands of TLR-2 to -9. Tracking cytokine production in PBMC initially revealed that a subset of TLR agonists including polyinosinic-polycytidylic acid (poly I:C), 3M-002, 3M-003, R-848 and single-stranded RNA trigger relatively high levels of IFN-gamma expression by NK cells. Isolated NK cells did not express TLR-7 or TLR-8. Unlike MALP-2 and poly I:C, 3M-001-3 did not induce expression of either CD69 or IFN-gamma by purified NK cells suggesting indirect activation. IL-18 and IL-12p70 were primarily required for induction of IFN-gamma by both synthetic and natural TLR-8 ligands, while type I IFN was required for induction of CD69 on NK cells by the TLR-7 agonist 3M-001. In addition to expression of IFN-gamma and CD69, relative induction of NK-cell cytotoxicity by TLR-7 and TLR-8 agonists was compared. Immune response modifiers (IRMs) with a TLR-8 agonist component (3M-002 and 3M-003) stimulated greater levels of K562 cytolysis than achieved with 3M-001 or IL-2 (1000 units ml(-1)). In vivo NK-cell cytotoxicity was also enhanced by R-848, but not in type I IFNR-deficient mice. We conclude that IRMs can modulate NK-cell function both in vitro and in vivo and that distinct indirect pathways control human NK-cell activation by TLR-7 and TLR-8 agonists.
Gorski
Kevin S
KS
3M Pharmaceuticals, Department of Pharmacology, 3M Center, 270-2S-06, St Paul, MN 55144, USA. kgorski@mmm.com
Waller
Emily L
EL
Bjornton-Severson
Jacqueline
J
Hanten
John A
JA
Riter
Christie L
CL
Kieper
William C
WC
Gorden
Keith B
KB
Miller
Jeffrey S
JS
Vasilakos
John P
JP
Tomai
Mark A
MA
Alkan
Sefik S
SS
D000818:Animals; D015703:Antigens, CD / Q000276:immunology; D000945:Antigens, Differentiation, T-Lymphocyte / Q000276:immunology; D016207:Cytokines / Q000276:immunology; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D007369:Interferon Inducers / Q000494:pharmacology*; D020014:K562 Cells; D007694:Killer Cells, Natural / Q000276:immunology*; D037181:Lectins, C-Type; D008024:Ligands; D008213:Lymphocyte Activation / Q000187:drug effects* / Q000276:immunology; D051379:Mice; D008817:Mice, Mutant Strains; D011804:Quinolines / Q000494:pharmacology; D017471:Receptors, Interferon / Q000276:immunology; D015398:Signal Transduction / Q000187:drug effects*; D051199:Toll-Like Receptor 7 / Q000819:agonists* / Q000276:immunology; D051200:Toll-Like Receptor 8 / Q000819:agonists* / Q000276:immunology; D000099192:CD69 Antigens
D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D016207:Cytokines; D007093:Imidazoles; D007369:Interferon Inducers; D037181:Lectins, C-Type; D008024:Ligands; D011804:Quinolines; D017471:Receptors, Interferon; D051199:Toll-Like Receptor 7; D051200:Toll-Like Receptor 8; D000099192:CD69 Antigens; C526117:3M 002; C495348:TLR7 protein, human; C495349:TLR8 protein, human