Functional activity of natural killer cells and killer T cells in mice after ovarian transplantation

Tashkent Postgraduate Medical Institute, Ministry of Health of the USSR. (Presented by Academician of the Academy of Medical Sciences of the USSR N. A. Lopatkin). Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 112, No. 9, pp. 273–275, September, 1991.     

The role of natural killer cells in autoimmune blistering diseases

The major focus of this paper is to describe and evaluate current information on the role of natural killer cells (NK cells) in the pathogenesis of blistering diseases. Until now, only pemphigus vulgaris (PV) has been studied. One co-culture study demonstrated that CD4⁺ T cells from the peripheral blood or perilesional skin of patients with active disease proliferate and secrete cytokines in the presence of major histocompatibility class II-expressing NK cells loaded with antigenic desmoglein self-peptides. Another study showed that NK cells can contribute to a T helper type 2-biased immune response through impaired interleukins (IL)-12 signaling and upregulation of IL, IL-10 and IL-5. Although significant data on other blistering diseases are unavailable at present, some studies implicate NK cells in disease progression. For instance, information on the role of NK cells in psoriasis and their production of tumor necrosis factor-α (TNF-α) will be provided since several TNF-α-inhibitors are used in its treatment. Studies on alopecia areata are also included in this paper because NK cells seem to play a key role in its pathogenesis. This review highlights the potential importance of NK cells and NKT cells as members of the large repertoire of cells and soluble mediators that play a critical role in pathogenesis of blistering diseases and other autoimmune diseases involving the skin. Therefore, the authors advocate a greater focus and interest on the study of the interaction of NK cells and the skin.     

Turned on by danger: activation of CD1d-restricted invariant natural killer T cells

CD1d-restricted invariant natural killer T (iNKT) cells bear characteristics of innate and adaptive lymphocytes, which allow them to bridge the two halves of the immune response and play roles in many disease settings. Recent work has characterized precisely how their activation is initiated and regulated. Novel antigens from important pathogens have been identified, as has an abundant self-antigen, β-glucopyranosylcaramide, capable of mediating an iNKT-cell response. Studies of the iNKT T-cell receptor (TCR)-antigen-CD1d complex show how docking between CD1d-antigen and iNKT TCR is highly conserved, and how small sequence differences in the TCR establish intrinsic variation in iNKT TCR affinity. The sequence of the TCR CDR3β loop determines iNKT TCR affinity for ligand-CD1d, independent of ligand identity. CD1d ligands can promote T helper type 1 (Th1) or Th2 biased cytokine responses, depending on the composition of their lipid tails. Ligands loaded into CD1d on the cell surface promote Th2 responses, whereas ligands with long hydrophobic tails are loaded endosomally and promote Th1 responses. This information is informing the design of synthetic iNKT-cell antigens. The iNKT cells may be activated by exogenous antigen, or by a combination of dendritic cell-derived interleukin-12 and iNKT TCR-self-antigen-CD1d engagement. The iNKT-cell activation is further modulated by recent foreign or self-antigen encounter. Activation of dendritic cells through pattern recognition receptors alters their antigen presentation and cytokine production, strongly influencing iNKT-cell activation. In a range of bacterial infections, dendritic cell-dependent innate activation of iNKT cells through interleukin-12 is the dominant influence on their activity.     

Alteration of T cells and natural killer cells during chickenpox in infancy

To determine the reasons for the low immune response and the mild morbidity of chickenpox in infancy, we investigated alteration of T cells and natural killer (NK) cells during chickenpox in children <1 year and 2 years old using flow cytometry. The CD4/CD8 ratio decreased only in the <1-year-old group from the acute to the convalescent phase (P<0.05). The CD3–CD16+CD56+ and CD57–CD16+ counts increased in the <1-year-old group, but those in the 2-year-old group did not increase from the acute to the convalescent phase. The CD3–CD16+CD56+ counts and the CD57-CD16+ counts and percentage were larger in the <1-year-old group than those in the 2-year-old group (P=0.001,P=0.002, andP<0.05) in the convalescent phase. These results seem to indicate that the low immune response in infancy after chickenpox are related to the small number of CD8 in contrast with CD4 and that increased subsets of NK cells during chickenpox may correlate to the mild morbidity of chickenpox in infancy.     

Carbohydrate specificity of the recognition of diverse glycolipids by natural killer T cells

Summary:  Most T lymphocytes recognize peptide antigens bound to or presented by molecules encoded in the major histocompatibility complex (MHC). The CD1 family of antigen-presenting molecules is related to the MHC-encoded molecules, but CD1 proteins present lipid antigens, mostly glycolipids. Here we review T-lymphocyte recognition of glycolipids, with particular emphasis on the subpopulation known as natural killer T (NKT) cells. NKT cells influence many immune responses, they have a T-cell antigen receptor (TCR) that is restricted in diversity, and they share properties with cells of the innate immune system. NKT cells recognize antigens presented by CD1d with hexose sugars in α-linkage to lipids, although other, related antigens are known. The hydrophobic alkyl chains are buried in the CD1d groove, with the carbohydrate exposed for TCR recognition, together with the surface of the CD1d molecule. Therefore, understanding the biochemical basis for antigen recognition by NKT cells requires an understanding of how the trimolecular complex of CD1d, glycolipid, and the TCR is formed, which is in part a problem of carbohydrate recognition by the TCR. Recent investigations from our laboratories as well as studies from other groups have provided important information on the structural basis for NKT-cell specificity.     

Human natural killer cell development

Summary:  Our understanding of human natural killer (NK) cell development lags far behind that of human B- or T-cell development. Much of our recent knowledge of this incomplete picture comes from experimental animal models that have aided in identifying fundamental in vivo processes, including those controlling NK cell homeostasis, self-tolerance, and the generation of a diverse NK cell repertoire. However, it has been difficult to fully understand the mechanistic details of NK cell development in humans, primarily because the in vivo cellular intermediates and microenvironments of this developmental pathway have remained elusive. Although there is general consensus that NK cell development occurs primarily within the bone marrow (BM), recent data implicate secondary lymphoid tissues as principal sites of NK cell development in humans. The strongest evidence stems from the observation that the newly described stages of human NK cell development are naturally and selectively enriched within lymph nodes and tonsils compared with blood and BM. In the current review, we provide an overview of these recent findings and discuss these in the context of existing tenets in the field of lymphocyte development.     

Intrahepatic and peripheral blood phenotypes of natural killer and T cells: differential surface expression of killer cell immunoglobulin‐like receptors

Deep characterization of the frequencies, phenotypes and functionalities of liver and peripheral blood natural killer (NK), natural killer T (NKT) and T cells from healthy individuals is an essential step to further interpret changes in liver diseases. These data indicate that CCR7, a chemokine essential for cell migration through lymphoid organs, is almost absent in liver NK and T cells. CD56^bright NK cells, which represent half of liver NK cells, showed lower expression of the inhibitory molecule NKG2A and an increased frequency of the activation marker NKp44. By contrast, a decrease of CD16 expression with a potential decreased capacity to perform antibody‐dependent cellular cytotoxicity was the main difference between liver and peripheral blood CD56^dim NK cells. Liver T cells with an effector memory or terminally differentiated phenotype showed an increased frequency of MAIT cells,T‐cell receptor‐γδ (TCR‐γδ) T cells and TCR‐αβ CD8⁺ cells, with few naive T cells. Most liver NK and T cells expressed the homing markers CD161 and CD244. Liver T cells revealed a unique expression pattern of killer cell immunoglobulin‐like receptors (KIR) receptors, with increased degranulation ability and higher secretion of interferon‐γ. Hence, the liver possesses a large amount of memory and terminally differentiated CD8⁺ cells with a unique expression pattern of KIR activating receptors that have a potent functional capacity as well as a reduced amount of CCR7, which are unable to migrate to regional lymph nodes. These results are consistent with previous studies showing that liver T (and also NK) cells likely remain and die in the liver.     

Subsets of human natural killer cells and their regulatory effects

Human natural killer (NK) cells have distinct functions as NK^tolerant, NK^cytotoxic and NK^regulatory cells and can be divided into different subsets based on the relative expression of the surface markers CD27 and CD11b. CD27⁺ NK cells, which are abundant cytokine producers, are numerically in the minority in human peripheral blood but constitute the large population of NK cells in cord blood, spleen, tonsil and decidua tissues. Recent data suggest that these NK cells may have immunoregulatory properties under certain conditions. In this review, we will focus on these new NK cell subsets and discuss how regulatory NK cells may serve as rheostats or sentinels in controlling inflammation and maintaining immune homeostasis in various organs.     

Human natural killer (NK) cells present staphylococcal enterotoxin B (SEB) to T lymphocytes

Superantigen-mediated T cell activation requires the participation of antigen-presenting cells (APC). Once superantigen has bound class II MHC molecules on the surface of APC, it then can interact with the T cell receptor to induce T cell activation. Superantigen-mediated T lymphocyte activation, along with its consequent cytokine production is thought to be the basis for the pathophysiology of conditions such as toxic shock syndrome, Kawasaki''s disease and possibly rheumatoid arthritis. We examined the role of CD56⁺ NK lymphocytes in the interaction between superantigens and T lymphocytes. First, we found that a subpopulation of CD56⁺ cells freshly isolated from human peripheral blood expressed class II MHC molecules. The amount of HLA-DR expression varied between individuals, ranging from 9.3% to 37.7%. CD56⁺ (NK) cells were purified from the peripheral blood by cell sorting and were tested for their ability to support SEB-mediated T cell activation as assessed by surface expression of IL-2 receptor α-chain (CD25) on CD3⁺ lymphocytes. We observed that when enriched T cells were incubated with SEB in the presence of NK cells, there was a significant up-regulation of CD25 expression on the T cells. When HLA-DR⁺ cells were removed from sorted CD56⁺ populations, the remaining HLA-DR⁻ NK cells were unable to support SEB-mediated T cell activation. Also, SEB up-regulated the expression of HLA-DR on CD56⁺ cells in peripheral blood mononuclear cell (PBMC) populations after 24 h of incubation, implying that the ability of NK cells to function as superantigen-presenting cells is up-regulated by superantigens themselves. Together, these data demonstrate for the first time that human CD56⁺HLA-DR⁺ NK cells can function as superantigen-presenting cells, and imply that NK cells may be involved in the activation of non-specific T cell reactivity during early host defences against superantigen-elaborating microorganisms in vivo. Furthermore, the physical linkage of NK cells and T cells by the interaction of superantigen with HLA class II molecules and T cell receptors, respectively, may lead to NK cell activation and augmented lytic potential, helping to clear the body of superantigen-elaborating microorganisms.     

人外周血自然杀伤T细胞体外扩增及其功能的初步研究

为了建立人自然杀伤T(NKT)细胞在体外扩增的方法并对其功能进行初步的研究,通过不同的方法从人外周血单个核细胞(MNC)和纯化T淋巴细胞中扩增TCRVα24+/Vβ11+NKT细胞,并采用流式细胞术测定NKT细胞中IL-4、IFN-γ、TNF-α分泌水平。采用CD4/CD8免疫磁珠去除CD4+和CD8+细胞进一步纯化NKT细胞,并用DIOC18染色及流式细胞术测定NKT细胞杀伤活性。α半乳糖神经酰胺(α-Galcer)和IL-2可以使NKT细胞在体外扩增。扩增19d后,TCRVα24+/Vβ11+细胞比率最高上升到25.5%±7.2%,NKT细胞最大扩增倍数达到(1.51±0.91)×104倍。体外扩增的NKT细胞高表达TCRVα24、Vβ11、CD3、CD161,低表达CD56。在CD3单克隆抗体和IL-2刺激下,TCRVβ11+细胞分泌IL-4和IFN-γ的细胞比例均高于TCRVβ11-细胞(P<0.05)。去除CD4+和CD8+细胞后NKT细胞含量上升到80%。NKT细胞对肿瘤细胞株U937和HL60以及树突状细胞具有较强的细胞毒效应。NKT细胞可以通过α-Galcer直接从人外周血MNC扩增获得,从而简化实验步骤。     

Taking license with natural killer cell maturation and repertoire development

Summary:  Combining population analysis with in-depth analysis of selected individuals, the tolerance of human natural killer (NK) cells to autologous major histocompatibility complex (MHC) class I and potential reactivity to allogeneic MHC class I have been studied. Analysis of NK cell clones in long-term culture and peripheral blood NK cells after short-term culture (20–24 h) shows that NK cell tolerance is determined by interactions of autologous MHC class I with CD94:NKG2A and inhibitory killer cell immunoglobulin-like receptors (KIRs). Alloreactivity is predicted whenever the donor of the allogeneic target lacks a cognate MHC class I–KIR, ligand–receptor pair that is present in the NK cell donor. In the human population, there is a wide variation in the NK cell repertoire of KIRs and CD94:NKG2A expression. Variation is principally due to KIR gene variation and polymorphism, with a smaller effect due to MHC class I. The presence of MHC class I increases the frequency of NK cells expressing the cognate KIR, an effect that is diminished by the presence of other cognate–ligand pairs. The minor influence of MHC class I on the KIR repertoire indicates that NK cell development is an efficient process in which the expression of inhibitory MHC class I receptors at the final stages ensures that functionally active human NK cells are self-tolerant.     

Frequency and phenotype of natural killer cells and natural killer cell subsets in bovine lymphoid compartments and blood

Natural killer (NK) cells are widely distributed in lymphoid and non‐lymphoid tissues, but little is known about the recirculation of NK cells between blood and tissues. This is relevant to understanding recirculation in the steady‐state and also for determining the roles for NK cells in vaccine‐induced immunity and responses to infection. Therefore, the percentage of NK cells and their phenotype across peripheral blood, afferent lymph and lymph nodes in steady‐state conditions was investigated in cattle using the pseudo‐afferent lymphatic cannulation model. CD2⁺ CD25^lo NK cells were the predominant subset of NK cells within the blood. In contrast, CD2⁻ CD25^hi NK cells were the main subset present within the skin‐draining afferent lymphatic vessels and lymph nodes, indicating that CD2⁻ NK cells are the principal NK cell subset trafficking to lymph nodes via the afferent lymphatic vessel. Furthermore, a low percentage of NK cells were present in efferent lymph, which were predominantly of the CD2⁻ subset, indicating that NK cells can egress from lymph nodes and return to circulation in steady‐state conditions. These compartmentalization data indicate that NK cells represent a population of recirculating lymphocytes in steady‐state conditions and therefore may be important during immune responses to vaccination or infection.     

Invariant natural killer T cells balance B cell immunity

Invariant natural killer T (iNKT) cells mediate rapid immune responses which bridge the gap between innate and adaptive responses to pathogens while also providing key regulation to maintain immune homeostasis. Both types of important iNKT immune responses are mediated through interactions with innate and adaptive B cells. As such, iNKT cells sit at the decision‐making fulcrum between regulating inflammatory or autoreactive B cells and supporting protective or regulatory B cell populations. iNKT cells interpret the signals in their environment to set the tone for subsequent adaptive responses, with outcomes ranging from getting licensed to maintain homeostasis as an iNKT regulatory cell (iNKT_reg) or being activated to become an iNKT follicular helper (iNKT_FH) cell supporting pathogen‐specific effector B cells. Here we review iNKT and B cell cooperation across the spectrum of immune outcomes, including during allergy and autoimmune disease, tumor surveillance and immunotherapy, or pathogen defense and vaccine responses. Because of their key role as influencers, iNKT cells provide a valuable target for therapeutic interventions. Understanding the nature of the interactions between iNKT and B cells will enable the development of clinical interventions to strategically target regulatory iNKT and B cell populations or inflammatory ones, depending on the circumstance.     

Interaction between natural killer cells and regulatory T cells: perspectives for immunotherapy

Regulatory T (Treg) cells and natural killer (NK) cells are key players in the immune system. The interaction between these two cell types has been reported to be beneficial in healthy conditions such as pregnancy. However, in the case of certain pathologies such as autoimmune diseases and cancer this interaction can become detrimental, as Treg cells have been described to suppress NK cells and in particular to impair NK cell effector functions. This review aims to discuss the recent information on the interaction between Treg cells and NK cells under healthy and pathologic conditions, to describe the specific conditions in which this interaction takes place, the effect of Treg cells on hematopoietic stem cell differentiation and the consequences of this interaction on the optimization of immunotherapeutic protocols.     

The biology of natural killer cells during sepsis

Natural killer (NK) cells are large granular lymphocytes largely recognized for their importance in tumour surveillance and the host response to viral infections. However, as the major innate lymphocyte population, NK cells also coordinate early responses to bacterial infections by amplifying the antimicrobial functions of myeloid cells, especially macrophages, by production of interferon‐γ (IFN‐γ). Alternatively, excessive NK cell activation and IFN‐γ production can amplify the systemic inflammatory response during sepsis resulting in increased physiological dysfunction and organ injury. Our understanding of NK cell biology during bacterial infections and sepsis is mostly derived from studies performed in mice. Human studies have demonstrated a correlation between altered NK cell functions and outcomes during sepsis. However, mechanistic understanding of NK cell function during human sepsis is limited. In this review, we will review the current understanding of NK cell biology during sepsis and discuss the challenges associated with modulating NK cell function during sepsis for therapeutic benefit.     

Simple enumerations of peripheral blood natural killer (CD56+ NK) cells, B cells and T cells have no predictive value in IVF treatment outcome

BACKGROUND: To evaluate the association between the absolute counts of the peripheral natural killer (NK) cells (including total CD56(+) NK cells, CD56(dim) NK cells and CD56(bright) NK cells), B cells and T cells on the implantation rate and miscarriage rate after IVF treatment. METHODS: This was a prospective observation study. A total of 138 patients who underwent IVF treatment from December 2002 to July 2003 were recruited to the study. Blood samples were obtained on the day of vaginal oocyte retrieval prior to the procedure. The absolute counts of lymphocytes, NK cells, B cells and T cells were identified by flow cytometry. These absolute counts and their relationships to IVF treatment outcome and miscarriage rate were analysed. RESULTS: There were no significant differences with regard the mean values of absolute lymphocyte count, T cell count, B cell count and NK cell count (including total CD56(+) NK, CD56(dim) NK and CD56(bright) NK cells) between the pregnant and non-pregnant groups and also between the ongoing pregnancy and miscarriage groups. The cause of infertility, duration of infertility, basal FSH levels, number of previous failed IVF treatments, number of previous miscarriages and stimulation characteristics were not significantly different between the pregnant and non-pregnant groups. Previous studies have suggested that women with a history of recurrent miscarriage and those with infertility accompanied by recurrent failed IVF treatments are associated with a peripheral blood NK cell percentage >12%, therefore further analysis of peripheral CD56(+) NK cell levels <12% (group A) and >12% (group B) was performed. There was no significant difference in implantation rate (group A: 17.0%; group B: 23.2%), pregnancy rate (group A: 36.6%; group B: 47.7%) or miscarriage rate (group A: 23.3%; group B: 28.6%). CONCLUSION: There were no significant differences between simple enumerations of peripheral blood NK cells (including total CD56(+) NK, CD56(dim) NK and CD56(bright) NK cells), B cells and T cells with IVF treatment outcome and pregnancy outcome. Women who had a peripheral NK cell level >12% did not have higher number of previous pregnancy losses. Importantly their pregnancy rate was not reduced and their miscarriages were not increased compared to women who had a peripheral NK cells level <12%.     

自然杀伤细胞的抗病毒活性

自然杀伤细胞是一类不同于T、B淋巴细胞的多功能淋巴细胞，在抗病毒免疫中发挥着重要作用。目前关于自然杀伤细胞参与抗病毒反应的研究主要集中于以下3点：①自然杀伤细胞介导抗病毒反应的路径；②自然杀伤细胞受体的功能；③自然杀伤细胞及自然杀伤T细胞在抗病毒反应中的激活和作用机理。尽管其中仍然存在许多悬而未决的问题，但大量的研究从分子水平揭示了自然杀伤细胞在病毒感染过程中的功能和反应。     

Analyses of phenotypic and functional characteristics of CX3CR1-expressing natural killer cells

We previously demonstrated a correlation between the frequency of CX3CR1-expressing human natural killer (NK) cells and disease activity in multiple sclerosis and showed that CX3CR1(high) NK cells were more cytotoxic than their CX3CR1(neg/low) counterparts. Here we aimed to determine whether human NK cell fractions defined by CX3CR1 represent distinct subtypes. Phenotypic and functional NK cell analyses revealed that, distinct from CX3CR1(high), CX3CR1(neg/low) NK cells expressed high amounts of type 2 cytokines, proliferated robustly in response to interleukin-2 and promoted a strong up-regulation of the key co-stimulatory molecule CD40 on monocytes. Co-expression analyses of CX3CR1 and CD56 demonstrated the existence of different NK cell fractions based on the surface expression of these two surface markers, the CX3CR1(neg) CD56(bright), CX3CR1(neg) CD56(dim) and CX3CR1(high) CD56(dim) fractions. Additional investigations on the expression of NK cell receptors (KIR, NKG2A, NKp30 and NKp46) and the maturation markers CD27, CD62L and CD57 indicated that CX3CR1 expression of CD56(dim) discriminated between an intermediary CX3CR1(neg) CD56(dim) and fully mature CX3CR1(high) CD56(dim) NK cell fractions. Hence, CX3CR1 emerges as an additional differentiation marker that may link NK cell maturation with the ability to migrate to different organs including the central nervous system.