Academic literature on the topic 'LOW MEMORY KILLER'

AbstractDuring mouse cytomegalovirus (CMV) infection, a population of Ly49H+ natural killer (NK) cells expands and is responsible for disease clearance through the induction of a “memory NK-cell response.” Whether similar events occur in human CMV infection is unknown. In the present study, we characterized the kinetics of the NK-cell response to CMV reactivation in human recipients after hematopoietic cell transplantation. During acute infection, NKG2C+ NK cells expanded and were potent producers of IFNγ. NKG2C+ NK cells predominately expressed killer cell immunoglobulin–like receptor, and self-killer cell immunoglobulin–like receptors were required for robust IFNγ production. During the first year after transplantation, CMV reactivation induced a more mature phenotype characterized by an increase in CD56dim NK cells. Strikingly, increased frequencies of NKG2C+ NK cells persisted and continued to increase in recipients who reactivated CMV, whereas these cells remained at low frequency in recipients without CMV reactivation. Persisting NKG2C+ NK cells lacked NKG2A, expressed CD158b, preferentially acquired CD57, and were potent producers of IFNγ during the first year after transplantation. Recipients who reactivated CMV also expressed higher amounts of IFNγ, T-bet, and IL-15Rα mRNA transcripts. Our findings support the emerging concept that CMV-induced innate memory-cell populations may contribute to malignant disease relapse protection and infectious disease control long after transplantation.

Growing evidence indicates the pronounced effects of physical activity on immune functions, which may largely depend on the type of exercise, intensity, and duration. However, limited information is available regarding the effects of low-impact exercises, especially on the level of adaptive immune system. Our study aimed to investigate and compare the changes in a broad spectrum of lymphocyte subtypes after 14 weeks of aerobic-type total-body-shaping workouts (TBSW) and Pilates workouts (PW) among healthy individuals. We determined the percentages of peripheral natural killer cells and different T and B lymphocyte subtypes with flow cytometry. At the end of the exercise program, significant changes in naïve and memory lymphocyte ratios were observed in TBSW group. Percentages of naïve cytotoxic T (Tc) cells elevated, frequencies of memory Tc and T-helper cell subsets decreased, and distribution of naïve and memory B cells rearranged. Proportions of activated T cells also showed significant changes. Nonetheless, percentages of anti-inflammatory interleukin (IL)-10-producing regulatory type 1 cells and immunosuppressive CD4+CD127lo/−CD25bright T regulative cells decreased not only after TBSW but also after PW. Although weekly performed aerobic workouts may have a more pronounced impact on the adaptive immune system than low-impact exercises, both still affect immune regulation in healthy individuals.

“Memory-like T cells” are a subset of thymic cells that acquire effector function through the maturation process rather than interaction with specific antigen. Disruption of genes encoding T cell signaling proteins or transcription factors have provided insights into the differentiation of such cells. In this study, we show that in BALB/c, but not C57BL/6, mice, a large portion of thymic CD4-CD8+ T cells exhibit a memory-like phenotype. In BALB/c mice, IL-4 secreted by invariant natural killer T (iNKT) cells is both essential and sufficient for the generation of memory-like T cells. In C57BL/6 mice, iNKT cells are less abundant, producing IL-4 that is insufficient to induce thymic memory-like CD8+ T cells. BALB/c mice deficient in the transcription factor Kruppel-like factor (KLF) 13 have comparable numbers of iNKT cells to C57BL/6 mice and extremely low levels of thymic memory-like CD8+ T cells. This work documents the impact of a small number of KLF13-dependent iNKT cells on the generation of memory-like CD8+ T cells.

ABSTRACTPrevious studies have shown that elite controllers with minimal effector T cell responses harbor a low-frequency, readily expandable, highly functional, and broadly directed memory population. Here, we interrogated thein vivorelevance of this cell population by investigating whether the breadth of expandable memory responses is associated with the magnitude of residual viremia in individuals achieving durable suppression of HIV infection. HIV-specific memory CD8+T cells were expanded by using autologous epitopic and variant peptides. Viral load was measured by an ultrasensitive single-copy PCR assay. Following expansion, controllers showed a greater increase in the overall breadth of Gag responses than did untreated progressors (P= 0.01) as well as treated progressors (P= 0.0003). Nef- and Env-specific memory cells expanded poorly for all groups, and their expanded breadths were indistinguishable among groups (P= 0.9 for Nef as determined by a Kruskal-Wallis test;P= 0.6 for Env as determined by a Kruskal-Wallis test). More importantly, we show that the breadth of expandable, previously undetectable Gag-specific responses was inversely correlated with residual viral load (r= −0.6;P= 0.009). Together, these data reveal a direct link between the abundance of Gag-specific expandable memory responses and prolonged maintenance of low-level viremia. Our studies highlight a CD8+T cell feature that would be desirable in a vaccine-induced T cell response.IMPORTANCEMany studies have shown that the rare ability of some individuals to control HIV infection in the absence of antiretroviral therapy appears to be heavily dependent upon special HIV-specific killer T lymphocytes that are able to inhibit viral replication. The identification of key features of these immune cells has the potential to inform rational HIV vaccine design. This study shows that a special subset of killer lymphocytes, known as central memory CD8+T lymphocytes, is at least partially involved in the durable control of HIV replication. HIV controllers maintain a large proportion of Gag-specific expandable memory CD8+T cells involved in ongoing viral suppression. These data suggest that induction of this cell subset by future HIV vaccines may be important for narrowing possible routes of rapid escape from vaccine-induced CD8+T cell responses.

Abstract Upon recognition of nonpeptidic phosphoantigens, human Vδ2 T lymphocytes enter a lineage differentiation pattern that determines the generation of memory cells with a range of effector functions. Here, we show that within the effector memory Vδ2 population, 2 distinct and complementary subsets with regard to phenotype, mode of activation, and type of responses can be identified: Vδ2 TEMh cells, which express high levels of chemokine receptors, but low levels of perforin and of natural killer receptors (NKRs) and which produce large amounts of interferon γ (IFN-γ) and tumor necrosis factor α (TNF-α) in response to T-cell receptor (TCR)–specific stimulation by phosphoantigens; and Vδ2TEMRA cells, which constitutively express several NKRs, high amounts of perforin, but low levels of chemokine receptors and of IFN-γ. These NK-like cells are refractory to phosphoantigen but respond to activation via FcγRIII (CD16) and are highly active against tumoral target cells. Thus, circulating Vδ2T lymphocytes comprise 2 functionally diverse subsets of effector memory cells that may be discriminated on the basis of CD16 expression.

Survival and intermittent proliferation of memory CD4+ and CD8+ T cells appear to be controlled by different homeostatic mechanisms. In particular, contact with interleukin (IL)-15 has a decisive influence on memory CD8+ cells, but not memory CD4+ cells. Past studies of memory CD4+ cells have relied heavily on the use of naturally occurring memory phenotype (MP) cells as a surrogate for antigen (Ag)-specific memory cells. However, we show here that MP CD4+ cells contain a prominent subset of rapidly proliferating major histocompatibility complex (MHC) II–dependent cells. In contrast, Ag-specific memory CD4 cells have a slow turnover rate and are MHC II independent. In irradiated hosts, these latter cells ignore IL-15 and expand in response to the elevated levels of IL-7 in the lymphopenic hosts. In contrast, in normal nonlymphopenic hosts where IL-7 levels are low, memory CD4 cells are heavily dependent on IL-15. Significantly, memory CD4+ responsiveness to endogenous IL-15 reflects marked competition from other cells, especially CD8+ and natural killer cells, and increases considerably after removal of these cells. Therefore, under normal physiological conditions, homeostasis of CD8+ and CD4+ memory cells is quite similar and involves IL-15 and IL-7.

Abstract Administration of posttransplant cyclophosphamide (PTCy) has significantly expanded the number of patients undergoing HLA-haploidentical hematopoietic cell transplantation (haplo-HCT). To examine immune reconstitution in these patients, we monitored T- and natural killer (NK)-cell recovery in 60 patients receiving bone marrow or peripheral blood stem cell (PBSC) grafts after haplo-HCT with PTCy and 35 patients receiving HLA-matched donor PBSC grafts with standard graft-versus-host disease (GVHD) prophylaxis. Compared with HLA-matched recipients, early T-cell recovery was delayed in haplo-HCT patients and skewed toward effector memory T cells with markedly reduced naive T cells. We found higher regulatory T (Treg)-cell/conventional T (Tcon)-cell ratios early after HCT and increased PD-1 expression on memory T cells. Within the haplo-HCT, patients who did not develop chronic GVHD (cGVHD) had higher PD-1 expression on central and effector memory CD4+ Treg cells at 1 month after transplant. These findings suggest an immunologic milieu that promotes immune tolerance in haplo-HCT patients. NK cells were decreased early after haplo-HCT with preferential expansion of immature CD56brightCD16− NK cells compared with matched donor transplants. One month after transplant, mass cytometry revealed enrichment of immature NK-cell metaclusters with high NKG2A, low CD57, and low killer-cell immunoglobulin-like receptor expression after haplo-HCT, which partially recovered 3 months post-HCT. At 2 months, immature NK cells from both groups were functionally impaired, but interleukin-15 priming corrected these defects in vitro. Increased immature/mature NK-cell ratios were associated with cytomegalovirus reactivation and increased incidence of cGVHD after haplo-HCT. These homeostatic imbalances in T- and NK-cell reconstitution after haplo-HCT reveal opportunities for early immune-based interventions to optimize clinical outcomes.

Abstract Introduction Infection is one of the main causes of mortality and morbidity after allogeneic stem cell transplantation, especially in patients who received T cell depleted haploidentical stem cells. Reactivation or de novo infection of cytomegalovirus (CMV) is amongst the most frequent complications and occur due to a lack of virus-specific T cells post-transplant. Pre-emptive immunotherapy may support both reconstitution of viral specific responses on one hand and may prevent impending leukemic relapse on the other hand. Therefore we established a protocol to generate CMV-specific cytokine-induced killer cells (CIKpp65) with dual cytolytic function against CMV and AML. Protocol CIK cells were generated in vitro from peripheral blood mononuclear cells (PBMC) of CMV-seropositive healthy donors using IFN-γ, activating monoclonal anti-CD3 antibody (MAb), interleukin (IL)-2 and IL-15. An additional single stimulation with human CMVpp65 protein was adequate to increase the amount of cytotoxic CMV-specificcells within CIK cells up to 23%. In total the CMVpp65 stimulation resulted in up to 11.0-fold increased frequency of CMV-dextramer+CD8+cells after 15 days of expansion (n=12). Results Cytotoxicity Next we investigated cell-mediated cytotoxicity against leukemic cell lines THP-1 and K562, pp65 loaded cell line T2 and CMV-infected primary fibroblasts. CIK cell cytotoxicity is described as mediated by activating NK-cell receptor NKG2D. This receptor was blocked in order to determine the specific MHC-mediated cytotoxicity in experiments targeting pp65 loaded cells. The lysis of pp65 loaded cells by CIKpp65 cells was significant higher as compared to conventional CIK cells (effector to target cell ratio of 5:1, 39.9±21.6% to 13.6±10.6%, P<0.01). CIKpp65 cells also induced high cytotoxicity in infected fibroblasts (up to 55%, 10:1 E:T ratio). The anti-leukemic effect was retained in CIKpp65 cells. CIKpp65 cells revealed a mean cytotoxicity of 71.5%, 60.7% and 37.8% against THP-1 and 55.0%, 50.0%, 20.5% against K562 in 40:1, 20:1 and 5:1 E:T ratio, respectively. In contrast, the reactivity against allogeneic PBMC remained low (18% lysis, 40:1 E:T ratio) and allogeneic mock-infected fibroblasts were not lysed at all. This clearly indicates towards the low alloreactive potential of CIKpp65 cells. Phenotype Furthermore we characterized subpopulation and memory phenotype of CIKpp65 cells in detailed flow cytometric analyses and examined the cytokine secretion pattern by cytometric bead array. After expansion the population mainly consisted of a CD3+CD56- T cell (77.6±4.5%) and CD3+CD56+ T-NK cell phenotype (20.0±12.6%). The T-NK cells additionally co-expressed high amounts of CD8 cytotoxic antigen (63.8±16.8%). Interestingly, the T-NK cell compartment contained higher amounts CMV-specific CD8+ cells (mean 5.5%) than the T cell compartment (mean 1.3%). Expression of activating NKG2D and CD25 receptor was strongly positive in both cell fractions. Remarkably, almost 30% of T-NK cells expressed γδ+ T cell receptor, whereas T cells only expressed 4.5% of this receptor type. The cytotoxic T cells within the CIKpp65 cells consisted of a mixed naïve (CD45RA+CD62L+), central memory (CD45RO+CD62L+) and effector memory (CD45RO+CD62L-) phenotype, the cytotoxic T-NK cells mainly of effector memory and EMRA (CD45RA+CD62L-) phenotype. Cytokine secretion (granzyme B, IFN-γ, MIP-1α, TNF-α, Fas-L, IP-10, IL-10, IL-6 and IL-4) were measured during the expansion period and cytotoxic assays and resulting data confirmed the cytotoxic nature of the cells and indicated towards a mainly TH1 cell type character. Conclusion In conclusion CIKpp65 cells can easily be generated from donor PBMC and might represent advantage to conventional CIK cells. Our pre-clinical data demonstrate the concomitant cytotoxicity of generated cells against leukemia cells and CMV, as well as low alloreactivity and limited risk to induce GvHD. Therefore CIKpp65 cells may represent an effective tool for pre-emptive immunotherapy in patients which have both an apparent risk of CMV reactivation and leukemic relapse after allogeneic stem cell transplantation. Disclosures No relevant conflicts of interest to declare.

Toxigenic mold activities produce metabolites that are either broad-spectrum antibiotics or mycotoxins that are cytotoxic. Indoor environmental exposure to these toxigenic molds leads to adverse health conditions with the main outcome measure of frequent neuroimmunologic and behavioral consequences. One of the immune system disorders found in patients presenting with toxigenic mold exposure is an abnormal natural killer cell activity. This paper presents an overview of the neurological significance of abnormal natural killer cell (NKC) activity in chronic toxigenic mold exposure. A comprehensive review of the literature was carried out to evaluate and assess the conditions under which the immune system could be dysfunctionally interfered with leading to abnormal NKC activity and the involvement of mycotoxins in these processes. The functions, mechanism, the factors that influence NKC activities, and the roles of mycotoxins in NKCs were cited wherever necessary. The major presentations are headache, general debilitating pains, nose bleeding, fevers with body temperatures up to 40�C (104�F), cough, memory loss, depression, mood swings, sleep disturbances, anxiety, chronic fatigue, vertigo/dizziness, and in some cases, seizures. Although sleep is commonly considered a restorative process that is important for the proper functioning of the immune system, it could be disturbed by mycotoxins. Most likely, mycotoxins exert some rigorous effects on the circadian rhythmic processes resulting in sleep deprivation to which an acute and transient increase in NKC activity is observed. Depression, psychological stress, tissue injuries, malignancies, carcinogenesis, chronic fatigue syndrome, and experimental allergic encephalomyelitis could be induced at very low physiological concentrations by mycotoxin-induced NKC activity. In the light of this review, it is concluded that chronic exposures to toxigenic mold could lead to abnormal NKC activity with a wide range of neurological consequences, some of which were headache, general debilitating pains, fever, cough, memory loss, depression, mood swings, sleep disturbances, anxiety, chronic fatigue, and seizures.

Abstract Human natural killer (NK) cells in peripheral blood perform many functions, and classification of specific subsets has been a longstanding goal. We report single-cell RNA sequencing of NK cells, comparing gene expression in unstimulated and interleukin (IL)-2–activated cells from healthy cytomegalovirus (CMV)-negative donors. Three NK cell subsets resembled well-described populations; CD56brightCD16−, CD56dimCD16+CD57−, and CD56dimCD16+CD57+. CD56dimCD16+CD57− cells subdivided to include a population with higher chemokine mRNA and increased frequency of killer-cell immunoglobulin-like receptor expression. Three novel human blood NK cell populations were identified: a population of type I interferon–responding NK cells that were CD56neg; a population exhibiting a cytokine-induced memory-like phenotype, including increased granzyme B mRNA in response to IL-2; and finally, a small population, with low ribosomal expression, downregulation of oxidative phosphorylation, and high levels of immediate early response genes indicative of cellular activation. Analysis of CMV+ donors established that CMV altered the proportion of NK cells in each subset, especially an increase in adaptive NK cells, as well as gene regulation within each subset. Together, these data establish an unexpected diversity in blood NK cells and provide a new framework for analyzing NK cell responses in health and disease.

Metastatic breast cancer treatment has seen few advances in recent years, yet treatment resistance continues to rise, causing disease recurrence. A pilot study was performed to determine the efficacy of ex vivo expansion and reprogramming of tumor-reactive immune cells from experimental metastatic tumor-sensitized mice. Also, phenotypic changes in tumors due to metastasis or tumor microenvironment influences were characterized. Metastatic neu+ mouse mammary carcinoma (mMMC) and its distant relapsing neu-antigen-negative variant (mANV) were investigated in FVBN202 mice. Tumor-reactive central memory CD8+ T cells and activated NK/NKT cells were successfully reprogrammed and expanded during 6-day expansion from mMMC- and/or mANV-sensitized mice, resulting in tumor-specific cytotoxicity. mMMC exhibited a flexible neu-expression pattern and acquired stem-like, tumorigenic phenotype following metastasis while mANV remained stable except decreased tumorigenicity. Myeloid-derived suppressor cell (MDSC) levels were not increased. Adoptive cellular therapy (ACT) with reprogrammed tumor-reactive immune cells may prove effective prophylaxis against metastatic or recurrent breast cancer.

No embedded system is possible without a memory inside as memory is important part of any system. So managing the memory is a crucial part of work in the System. That is why memory management is the most complex part of operating system. Whenever an operating system is decided for any devices the device memory and OS capabilities are matched. Choice of Android for the Mobile Phones give best combination of under lying hardware and software capabilities. In lined with the choice of OS, Android provides improved Memory Management than Linux. Android also provides the in build policy for handling with the low memory scenarios. But as the performance has no limit to achieve and daily user requirements for faster and bulky software needs further optimizations. Here in this thesis our aim is to focus on the RAM availability for the System. More system RAM means improved sluggish behavior with enhanced degree of multi programming and responsiveness. We studied various method of in kernel compression to achieve goal of improved RAM. These methods are Com-Cache, zSWAP, KSM. These methods are not in the proper shape to use with Android Operating System and Android Low Memory Policy situation. After deep analysis here to enhance the RAM availability we need to change the Android Low Memory Policy and modified com-cache and KSM implementations to suite the Mobile Phones. KSM utilizes the CPU heavily and drain out battery very fast and Com-Cache is not compatible with the LMK in its raw form. These techniques are modified and also changed Android Low memory Policy and these results in batter RAM availability to the system.