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

A Signal Peptide Derived from hsp60 Binds HLA-E and Interferes with CD94/NKG2A Recognition

Human histocompatibility leukocyte antigen (HLA)-E is a nonclassical major histocompatibility complex (MHC) class I molecule which presents a restricted set of nonameric peptides, derived mainly from the signal sequence of other MHC class I molecules. It interacts with CD94/NKG2 receptors expressed on the surface of natural killer (NK) cells and T cell subsets. Here we demonstrate that HLA-E also presents a peptide derived from the leader sequence of human heat shock protein 60 (hsp60). This peptide gains access to HLA-E intracellularly, resulting in up-regulated HLA-E/hsp60 signal peptide cell-surface levels on stressed cells. Notably, HLA-E molecules in complex with the hsp60 signal peptide are no longer recognized by CD94/NKG2A inhibitory receptors. Thus, during cellular stress an increased proportion of HLA-E molecules may bind the nonprotective hsp60 signal peptide, leading to a reduced capacity to inhibit a major NK cell population. Such stress induced peptide interference would gradually uncouple CD94/NKG2A inhibitory recognition and provide a mechanism for NK cells to detect stressed cells in a peptide-dependent manner

The frequency of CD127low expressing CD4+CD25high T regulatory cells is inversely correlated with human T lymphotrophic virus type-1 (HTLV-1) proviral load in HTLV-1-infection and HTLV-1-associated myelopathy/tropical spastic paraparesis

<p>Abstract</p> <p>Background</p> <p>CD4⁺CD25^highregulatory T (T_Reg) cells modulate antigen-specific T cell responses, and can suppress anti-viral immunity. In HTLV-1 infection, a selective decrease in the function of T_Regcell mediated HTLV-1-tax inhibition of FOXP3 expression has been described. The purpose of this study was to assess the frequency and phenotype of T_Regcells in HTLV-1 asymptomatic carriers and in HTLV-1-associated neurological disease (HAM/TSP) patients, and to correlate with measures of T cell activation.</p> <p>Results</p> <p>We were able to confirm that HTLV-I drives activation, spontaneous IFNγ production, and proliferation of CD4+ T cells. We also observed a significantly lower proportion of CTLA-4⁺T_Regcells (CD4⁺CD25^highT cells) in subjects with HAM/TSP patients compared to healthy controls. Ki-67 expression was negatively correlated to the frequency of CTLA-4⁺T_Regcells in HAM/TSP only, although Ki-67 expression was inversely correlated with the percentage of CD127^lowT_Regcells in healthy control subjects. Finally, the proportion of CD127^lowT_Regcells correlated inversely with HTLV-1 proviral load.</p> <p>Conclusion</p> <p>Taken together, the results suggest that T_Regcells may be subverted in HAM/TSP patients, which could explain the marked cellular activation, spontaneous cytokine production, and proliferation of CD4⁺T cells, in particular those expressing the CD25^highCD127^lowphenotype. T_Regcells represent a potential target for therapeutic intervention for patients with HTLV-1-related neurological diseases.</p

Cell-Mediated Immune Responses and Immunopathogenesis of Human Tick-Borne Encephalitis Virus-Infection

Tick-borne encephalitis virus (TBEV) is a flavivirus that belongs to the Flaviviridae family. TBEV is transmitted to humans primarily from infected ticks. The virus causes tick-borne encephalitis (TBE), an acute viral disease that affects the central nervous system (CNS). Infection can lead to acute neurological symptoms of significant severity due to meningitis or meningo(myelo)encephalitis. TBE can cause long-term suffering and has been recognized as an increasing public health problem. TBEV-affected areas currently include large parts of central and northern Europe as well as northern Asia. Infection with TBEV triggers a humoral as well as a cell-mediated immune response. In contrast to the well-characterized humoral antibody-mediated response, the cell-mediated immune responses elicited to natural TBEV-infection have been poorly characterized until recently. Here, we review recent progress in our understanding of the cell-mediated immune response to human TBEV-infection. A particular emphasis is devoted to studies of the response mediated by natural killer (NK) cells and CD8 T cells. The studies described include results revealing the temporal dynamics of the T cell- as well as NK cell-responses in relation to disease state and functional characterization of these cells. Additionally, we discuss specific immunopathological aspects of TBEV-infection in the CNS

Influenza A Virus Infection Induces Hyperresponsiveness in Human Lung Tissue-Resident and Peripheral Blood NK Cells

NK cells in the human lung respond to influenza A virus- (IAV-) infected target cells. However, the detailed functional capacity of human lung and peripheral blood NK cells remains to be determined in IAV and other respiratory viral infections. Here, we investigated the effects of IAV infection on human lung and peripheral blood NK cells in vitro and ex vivo following clinical infection. IAV infection of lung- and peripheral blood-derived mononuclear cells in vitro induced NK cell hyperresponsiveness to K562 target cells, including increased degranulation and cytokine production particularly in the CD56brightCD16− subset of NK cells. Furthermore, lung CD16− NK cells showed increased IAV-mediated but target cell-independent activation compared to CD16+ lung NK cells or total NK cells in peripheral blood. IAV infection rendered peripheral blood NK cells responsive toward the normally NK cell-resistant lung epithelial cell line A549, indicating that NK cell activation during IAV infection could contribute to killing of surrounding non-infected epithelial cells. In vivo, peripheral blood CD56dimCD16+ and CD56brightCD16− NK cells were primed during acute IAV infection, and a small subset of CD16−CD49a+CXCR3+ NK cells could be identified, with CD49a and CXCR3 potentially promoting homing to and tissue-retention in the lung during acute infection. Together, we show that IAV respiratory viral infections prime otherwise hyporesponsive lung NK cells, indicating that both CD16+ and CD16− NK cells including CD16−CD49a+ tissue-resident NK cells could contribute to host immunity but possibly also tissue damage in clinical IAV infection

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

Decoding NK cell receptor specificity : Functional and structural studies of MHC class 1 subcomponents

Natural Killer (NK) cells are an important part of the innate immune system. They can lyse target cells and secrete immunoregulatory cytokines early during immune responses. They mediate protection against viruses and tumours, and can reject MHC class I mismatched bone marrow grafts. NK cell function is regulated through activating and inhibitory receptors, many of which recognize MHC class I molecules on the surface of surrounding cells. The overall aim of this thesis has been to elucidate the MHC class I specificity of NK cell receptors. We have investigated the role of the heavy chain, the beta2m subunit and the peptide of MHC class I complexes in the interaction with NK cell receptors, primarily Ly49 receptors in the mouse and CD94/NKG2 receptors in the human. The MHC class I specificity of NK cell receptors was studied by direct visualisation using soluble, fluorescently labelled MHC class I tetramers, by X-ray crystallography and in functional assays. After having established the novel technique of soluble, fluorescently labelled tetrameric MHC class I molecules in our laboratory, we assessed the binding of such MHC class I tetramers (H-2D , 14- 2Kb and H-2D) to different Ly49 receptors. We could demonstrate that they bind in an allelespecific manner to Ly49 receptors and concluded that the MHC class I associated glycosylation was not required for the interaction between H-2Dd , H-2Db and Ly49A, nor for the interaction between H-2Kb, H-2Db and Ly49C. Furthermore we could show that the interaction between Ly49C and H-2Kb was peptide-selective, confirming and extending earlier functional data from our laboratory in a direct binding assay. Finally we identified H-2D b as a new ligand for both Ly49A and Ly49C. The role of the MHC class I bound beta2M subunit in recognition by Ly49 receptors was investigated using MHC class I tetramers of H-2Dd , H-2Kb and H-2Db refolded with either mouse or human beta2m. The change from mouse to human beta2m resulted in a loss of binding of all three MHC class I tetramers to Ly49A and Ly49C, indicating that both these receptors bind to MHC class I in a similar manner, partly involving the beta2m-subunit. To investigate the influence of beta2m on the structure of MHC class 1, in particular in relation to recognition by Ly49 receptors, we crystallized and solved the structures of H-2Db in complex with an LCMV derived peptide and either human or mouse beta2m. This allowed us for the first time to make a comparative analysis of two MHC class I crystal structures where only the 02M subunit differed. Despite over 30% difference in sequence between mouse and human beta2m, the conformation of the peptide and the peptide-binding groove were strikingly similar between the structures. The structures implicate that the lack of Ly49 recognition conferred by human beta2m is a direct consequence of the change from a glutamine to a glycine at position 29 in human beta2m, rather than distal conformational changes. Finally, we identified two heat shock protein 60 (hsp60) derived peptides that readily bind to HLA-E. We demonstrated that HLA-E in complex with these peptides abrogated recognition by the inhibitory CD94/NKG2A receptor, both in binding assays and functional assays. Our results suggest that there is an increased proportion of HLA-E molecules in complex with non-protective hsp60-derived peptides during cellular stress, and consequently a reduced inhibition of CD94/NKG2A+ NK cells. This phenomenon, which we term stress-induced peptide interference (SPI), provides a novel mechanism for NK cells to detect stressed cells in a peptide-dependent manner. In conclusion, our data supports the notion that both human and mouse NK cells have evolved a repertoire of MHC class I specific receptors which are sensitive to perturbations in all subcomponents of the MHC class I molecul

Calcium Intake and Serum Concentration in Relation to Risk of Cardiovascular Death in NHANES III

BACKGROUND: Evidence for an association between calcium intake and risk of cardiovascular death remains controversial. By assessing dietary intake, use of supplements, and serum levels of calcium, we aimed to disentangle this link in the third National Health and Nutrition Examination Survey (NHANES III). METHODS: Mortality linkage of NHANES III to death certificate data for those aged 17 years or older (n = 20,024) was used to estimate risk of overall cardiovascular death as well as death from ischemic heart disease (IHD), acute myocardial infarction (AMI), heart failure (HF), and cerebrovascular disease (CD) with multivariate Cox proportional hazards regression analysis. RESULTS: About 10.0% of the population died of cardiovascular disease and the majority (5.4%) died of IHD. There was increased risk of overall CVD death for those in the bottom 5% of serum calcium compared to those in the mid 90% (HR: 1.51 (95% CI: 1.03-2.22)). For women there was a statistically significant increased risk of IHD death for those with serum calcium levels in the top 5% compared to those in the mid 90% (HR: 1.72 (95%CI: 1.13-2.61)), whereas in men, low serum calcium was related to increased IHD mortality (HR: 2.32 (95% CI 1.14-3.01), Pinteraction: 0.306). No clear association with CVD death was observed for dietary or supplemental calcium intake. CONCLUSIONS: Calcium as assessed by serum concentrations is involved in cardiovascular health, though differential effects by sex may exist. No clear evidence was found for an association between dietary or supplementary intake of calcium and cardiovascular death

Calcium Intake and Serum Concentration in Relation to Risk of Cardiovascular Death in NHANES III

BACKGROUND: Evidence for an association between calcium intake and risk of cardiovascular death remains controversial. By assessing dietary intake, use of supplements, and serum levels of calcium, we aimed to disentangle this link in the third National Health and Nutrition Examination Survey (NHANES III). METHODS: Mortality linkage of NHANES III to death certificate data for those aged 17 years or older (n = 20,024) was used to estimate risk of overall cardiovascular death as well as death from ischemic heart disease (IHD), acute myocardial infarction (AMI), heart failure (HF), and cerebrovascular disease (CD) with multivariate Cox proportional hazards regression analysis. RESULTS: About 10.0% of the population died of cardiovascular disease and the majority (5.4%) died of IHD. There was increased risk of overall CVD death for those in the bottom 5% of serum calcium compared to those in the mid 90% (HR: 1.51 (95% CI: 1.03-2.22)). For women there was a statistically significant increased risk of IHD death for those with serum calcium levels in the top 5% compared to those in the mid 90% (HR: 1.72 (95%CI: 1.13-2.61)), whereas in men, low serum calcium was related to increased IHD mortality (HR: 2.32 (95% CI 1.14-3.01), Pinteraction: 0.306). No clear association with CVD death was observed for dietary or supplemental calcium intake. CONCLUSIONS: Calcium as assessed by serum concentrations is involved in cardiovascular health, though differential effects by sex may exist. No clear evidence was found for an association between dietary or supplementary intake of calcium and cardiovascular death