NK cells • Large granular lymphocytes • ~5-15% human peripheral blood lymphocytes • ~2-3% mouse spleen cells • “non-specific” cytotoxicity • standard targets K562 for human • YAC-1 for mouse • Cytokine production (IFNg, TNFa etc.) • CD56+CD3- CD16+ (human) • NK1.1+CD3- (mouse)
Antigen specific MHC-restricted Requires priming (takes days to respond) Memory Antigen non-specific MHC non-restricted Priming not required (rapid response, hours) No memory Cytotoxic T cells and NK cells Cytotoxic T cells NK cells
Various ways NK cells kill target cells TRAIL (TNF-Related Apoptosis- Inducing Ligand) ADCC (Antibody Dependent Cell Mediated Cytotoxicity) TNFa Direct cytotoxicity NK NK NK NK CD16 target target target target
Killing: Perforins & Granzymes CTL or NK Cell granules contain perforin and granzymes. granzymes perforins +Ca++ Endocytosis Storage Vesicle Movement along actin/ microtubule fibers. Nucleus Osmotic Lysis Cleavage & activation of caspases. Apoptosis! Transport of Gra B to nucleus.
MHC class I MHC is used as a marker for self vs non-self by the immune system.
Recognition of foreign vs self by cytotoxic T cells Cytotoxic T cell T cells recognize ‘foreign’. kill peptide MHC cell Self MHC + foreign peptide foreign MHC + foreign peptide Self MHC + self peptide No MHC
Recognition of foreign vs self by NK cells NK cell NK cells recognize non-self (missing self) kill peptide MHC cell Self MHC + foreign peptide foreign MHC + foreign peptide Self MHC + self peptide No MHC
MHC class I-specific inhibitory receptors on NK cells NK cell No activation activation activation Inhibitory receptor Activation receptor Foreign MHC Self- MHC No MHC
Inhibitory receptors on NK cells:signaling ITIM (Immunoreceptor Tyrosine-based Inhibitory Motif) Inhibitory receptor p p Activation receptor SHP1 phosphatase Src-family kinases dephosphorylation
NK cells: recognition of self vs non-self MHC +ve MHC -ve Eriksson et al. J Exp Med 190:1005, 1999 NK cells recognize self-MHC class I.
NK cell receptors for MHC class I LIR (ILT)-1 KIR (>13) CD94/NKG2 (4) Lectin- like family Human Immunoglobulin family Ly-49 (>10) CD94/NKG2 (3) Mouse
Human NK receptors: KIR (killer immunoglobulin-like receptors) 2DL 2DS 2DL4 3DL 3DS
H Mouse NK receptors for MHC class I Non-classical MHC class I Qa-1b peptide Classical MHC class I (H-2Dd, Kb etc.) Ly49 family CD94/NKG2 A C E A C D E F G I J
MHC class I specificity of Ly49 Ly49 MHC class I A B C D E F GH I J Dd, Dk ?? Kb, Kk, Kd, Dd, Db, Dk Dd ? H-2d ? Dd ? Kb, Kd ? ?
Ly49A Ly49B Ly49C Ly49D Ly49E Ly49F Ly49G Ly49H Ly49I Ly49J 1 10 20 30 40 50 60 70 80 CD94 NKG2A NKG2C NKG2E Co-expression of multiple receptors on individual NK cells • NK cells are very heterogenous can recognize different targets. • Most NK cells express at least one receptor specific for self MHC class I maintain self-tolerance.
NK cell activating receptors We know much about inhibitory receptors on NK cells, but how about activating receptors? Ly49D, H ? More activating receptors are to be found.
NK cells inhibit growth of tumors expressing NKG2D ligands Tumor growth in mice Lung metastasis of melanoma From Nature 413: 165, 2001 Diefenbech et al.
Diversity of human NK receptors KIRs Haplotype diversity and allelic polymorphism Almost everybody differs from each other in KIRs. All NK cells express at least one inhibitory receptor for self MHC.
Bone marrow cell transplantation and NK cells: graft versus leukemia without GVH ? Science 295:2097, 2002 In HLA-mismatched bone marrow transplantation, some donor-derived NK cells are not inhibited by host HLA and kill leukemia cells expressing host HLA. Donor NK cells also kill host antigen presenting cells and prevent GVHD.