Killer Cell Immunoglobulin-like Receptor Workshop: Insights into Evolution, Genetics, Function, and Translation

The seventh killer cell immunoglobulin-like receptor (KIR) workshop was held at Tammsvik, Stockholm, Sweden, in the summer of 2011. This intimate and isolated setting brought together approximately 100 investigators, from a range of scientific disciplines, who are all actively working on KIRs in humans or closely related primate species

Characterization of Natural Killer Cell Phenotype and Function during Recurrent Human HSV-2 Infection

Human natural killer (NK) cell differentiation, characterized by a loss of NKG2A in parallel with the acquisition of NKG2C, KIRs, and CD57 is stimulated by a number of virus infections, including infection with human cytomegalovirus (CMV), hantavirus, chikungunya virus, and HIV-1. Here, we addressed if HSV-2 infection in a similar way drives NK cell differentiation towards an NKG2A-NKG2C+KIR+CD57+ phenotype. In contrast to infection with CMV, hantavirus, chikungunya virus, and HIV-1, recurrent HSV-2 infection did not yield an accumulation of highly differentiated NK cells in human peripheral blood. This outcome indicates that human HSV-2 infection has no significant imprinting effect on the human NK cell repertoire

Systemic and Intra-Nodal Activation of NK Cells After Rituximab Monotherapy for Follicular Lymphoma

Monotherapy with the anti-CD20 monoclonal antibody rituximab can induce complete responses (CR) in patients with follicular lymphoma (FL). Resting FcRγIII+ (CD16+) natural killer (NK) cells respond strongly to rituximab-coated target cells in vitro. Yet, the contribution of NK cells in the therapeutic effect in vivo remains unknown. Here, we followed the NK cell repertoire dynamics in the lymph node and systemically during rituximab monotherapy in patients with FL. At baseline, NK cells in the tumor lymph node had a naïve phenotype albeit they were more differentiated than NK cells derived from control tonsils as determined by the frequency of CD56dim NK cells and the expression of killer cell immunoglobulin-like receptors (KIR), CD57 and CD16. Rituximab therapy induced a rapid drop in NK cell numbers coinciding with a relative increase in the frequency of Ki67+ NK cells both in the lymph node and peripheral blood. The Ki67+ NK cells had slightly increased expression of CD16, CD57 and higher levels of granzyme A and perforin. The in vivo activation of NK cells was paralleled by a temporary loss of in vitro functionality, primarily manifested as decreased IFNγ production in response to rituximab-coated targets. However, patients with pre-existing NKG2C+ adaptive NK cell subsets showed less Ki67 upregulation and were refractory to the loss of functionality. These data reveal variable imprints of rituximab monotherapy on the NK cell repertoire, which may depend on pre-existing repertoire diversity

Functional SARS-CoV-2 cross-reactive CD4+ T cells established in early childhood decline with age.

Pre-existing SARS-CoV-2-reactive T cells have been identified in SARS-CoV-2-unexposed individuals, potentially modulating COVID-19 and vaccination outcomes. Here, we provide evidence that functional cross-reactive memory CD4+ T cell immunity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is established in early childhood, mirroring early seroconversion with seasonal human coronavirus OC43. Humoral and cellular immune responses against OC43 and SARS-CoV-2 were assessed in SARS-CoV-2-unexposed children (paired samples at age two and six) and adults (age 26 to 83). Pre-existing SARS-CoV-2-reactive CD4+ T cell responses targeting spike, nucleocapsid, and membrane were closely linked to the frequency of OC43-specific memory CD4+ T cells in childhood. The functional quality of the cross-reactive memory CD4+ T cell responses targeting SARS-CoV-2 spike, but not nucleocapsid, paralleled OC43-specific T cell responses. OC43-specific antibodies were prevalent already at age two. However, they did not increase further with age, contrasting with the antibody magnitudes against HKU1 (β-coronavirus), 229E and NL63 (α-coronaviruses), rhinovirus, Epstein-Barr virus (EBV), and influenza virus, which increased after age two. The quality of the memory CD4+ T cell responses peaked at age six and subsequently declined with age, with diminished expression of interferon (IFN)-γ, interleukin (IL)-2, tumor necrosis factor (TNF), and CD38 in late adulthood. Age-dependent qualitative differences in the pre-existing SARS-CoV-2-reactive T cell responses may reflect the ability of the host to control coronavirus infections and respond to vaccination

Remodeling of secretory lysosomes during education tunes functional potential in NK cells

Inhibitory signaling during natural killer (NK) cell education translates into increased responsiveness to activation;however, the intracellular mechanism for functional tuning by inhibitory receptors remains unclear. Secretory lysosomes are part of the acidic lysosomal compartment that mediates intracellular signalling in several cell types. Here we show that educated NK cells expressing self-MHC specific inhibitory killer cell immunoglobulin-like receptors (KIR) accumulate granzyme B in dense-core secretory lysosomes that converge close to the centrosome. This discrete morphological phenotype is independent of transcriptional programs that regulate effector function, metabolism and lysosomal biogenesis. Meanwhile, interference of signaling from acidic Ca2+ stores in primary NK cells reduces target-specific Ca2+-flux, degranulation and cytokine production. Furthermore, inhibition of PI (3,5) P-2 synthesis, or genetic silencing of the PI(3,5) P-2-regulated lysosomal Ca2+-channel TRPML1, leads to increased granzyme B and enhanced functional potential, thereby mimicking the educated state. These results indicate an intrinsic role for lysosomal remodeling in NK cell education

Rapid expansion and long-term persistence of elevated NK cell numbers in humans infected with hantavirus

Acute hantavirus infection in humans triggers a rapid expansion and long-term persistence of NK cells

Robust T cell immunity in convalescent individuals with asymptomatic or mild COVID-19

SARS-CoV-2-specific memory T cells will likely prove critical for long-term immune protection against COVID-19. Here, we systematically mapped the functional and phenotypic landscape of SARS-CoV-2-specific T cell responses in unexposed individuals, exposed family members, and individuals with acute or convalescent COVID-19. Acute-phase SARS-CoV-2-specific T cells displayed a highly activated cytotoxic phenotype that correlated with various clinical markers of disease severity, whereas convalescent-phase SARS-CoV-2-specific T cells were polyfunctional and displayed a stem-like memory phenotype. Importantly, SARS-CoV-2-specific T cells were detectable in antibody-seronegative exposed family members and convalescent individuals with a history of asymptomatic and mild COVID-19. Our collective dataset shows that SARS-CoV-2 elicits broadly directed and functionally replete memory T cell responses, suggesting that natural exposure or infection may prevent recurrent episodes of severe COVID-19

Mechanisms of immune escape : Implications for immunotherapy against cancer

Tumor cells can be recognized and killed by cytotoxic T cells specific for certain tumor antigens. Immune mediated selection pressure along with genetic instability of tumor cells result in a growth advantage of tumor cells that acquire a less immunogenic phenotype. Increased understanding of immune escape mechanisms is crucial for the development of effective immunotherapy against cancer. This thesis deals with several aspects of immune escape and tumor induced immune suppression. We demonstrate the paradoxical finding that IFN-gamma treatment of short-term ovarian cancer cell lines (OVAC) protected these from cytotoxic T Lymphocyte (CTL) lysis. This was dependent on enhanced signaling to inhibitory NK receptors (iNKR), CD94/NKG2A, which were expressed by the CTLs. The ligand for CD94/NKG2A is HLA-E, which is a non-classical HLA class I molecule. HLA-E expression depends on its association with leader sequence peptides derived from classical and non-classical HLA class I molecules. Furthermore, the signaling capacity of the HLA-E / peptide complex is influenced by specific properties of the peptide that is bound to the HLA-E molecule. The leader sequence peptide of another non-classical HLA class I molecule, HLA-G, provides a particularly strong inhibitory signal to CD94/NKG2A receptors when bound in the peptide groove of the HLA-E molecule. Ovarian carcinomas were found to frequently express HLA-G at the protein level and HLA-E on a transcriptional level. The expression of both these molecules was induced by IFNgamma. We speculated that the increased intracellular accessibility to HLA-G leader sequence peptides (Gsp), followed by increased surface expression of HLA-E / Gsp complexes, was the underlying mechanism behind the IFN-gamma mediated protection of tumor cells. In support of this possibility we were able to mimic the effect of IFN-gamma by exogenously adding synthetic HLA-G leader sequence peptides to untreated tumor cells. It is concluded that IFN-gamma may shift the balance towards inhibitory signaling to the CTLs, turning off the lysis of otherwise sensitive targets. The role of such ligand - iNKR interactions deserves further attention in future attempts of immunotherapy against ovarian carcinoma. Ile importance of inhibitory NK receptors was further emphasized by the phenotypic analysis of ovarian tumor associated T and NK cells. There was a bias towards expression of inhibitory CD94/NKG2A receptors on the tumor infiltrating CD56+ T cells as compared to CD56+ T cells derived from PBL of patients and healthy donors. Further, there was an over-representation of regulatory, non-cytotoxic, CD56bright NK cells among the tumor associated lymphocytes. This was associated with high expression of inhibitory CD94/NKG2A receptors on this subset of NK cells. Expression of inhibitory receptors by a large number of tumor associated lymphocytes is likely to decrease their cytotoxic activity against autologous tumors. Hydrogen peroxide, released by tumor associated macrophages severely impairs the cytokine production and cytolytic function of T and NK cells. It was demonstrated that the Th1 cytokine production of T cells with an activated/memory (CD45RO+) phenotype was more sensitive than naive T cells to the influence of H202. Furthermore, the reduced Th1 cytokine production was associated with a block of NF-kappaB activation. The majority of tumor infiltrating lymphocytes is of a CD45RW phenotype and our results may explain why T cells that reside in tumor lesions often display anergic properties. Based on these results we speculated that exogenous supply of antioxidants may protect immune cells from the attack of free radicals. This hypothesis was tested on 12 patients with advanced colorectal cancer who were given high doses of dietary vitamin E during a period of two weeks. In a majority of patients the supplementation of vitamin E lead to enhanced IL-2 and IFN-gamma production by their T cells. Moreover, CD4/CD8 ratios were increased after treatment with vitamin E. It is concluded that the administration of dietary vitamin E may counter-act tumor induced immune suppression and form an effective supplement to more specific immunotherapy

Pan-cancer profiling of tumor-infiltrating natural killer cells through transcriptional reference mapping

<p>We generated a comprehensive reference atlas of human NK cells, based on single-cell RNA sequencing profiles from 72,129 cells obtained from bulk (12 donors) and sorted phenotypically-defined NK cell subsets (2 donors) and tissue-resident NK cells (TrNK, 136 donors). 38,862 tumor-infiltrating NK cells (TiNK) were extracted from datasets comprising seven solid tumor types (427 patients) and incorporated into our reference map using transfer learning. Both the NK data as well as the data form tumors/tissues with all the other cell types can be found here.</p&gt

Pan-cancer profiling of tumor-infiltrating natural killer cells through transcriptional reference mapping

<p>We generated a comprehensive reference atlas of human NK cells, based on single-cell RNA sequencing profiles from 72,129 cells obtained from bulk (12 donors) and sorted phenotypically-defined NK cell subsets (2 donors) and tissue-resident NK cells (TrNK, 136 donors). 38,862 tumor-infiltrating NK cells (TiNK) were extracted from datasets comprising seven solid tumor types (427 patients) and incorporated into our reference map using transfer learning. Both the NK data as well as the data form tumors/tissues with all the other cell types can be found here.</p&gt