Programmed cell death 1 (PD-1) is critical for T regulatory cells (Tregs) to maintain peripheral tolerance to self-antigens. In the tumor microenvironment, interaction between PD-1 and its ligands supports tumor immune evasion. Pembrolizumab blocks interactions of PD-1 with its ligands, enhancing antitumor and clinical responses. We and others have reported that pembrolizumab does not affect function or phenotype of thymic-derived Tregs; however, little is known about its effect on extrathymic differentiation of peripheral Tregs. In this study, we investigated the effect of pembrolizumab on in vitro-induced Tregs (iTregs). Our work showed that PD-1 blockade interferes with iTreg differentiation and has no potential effect on the stability of FOXP3 after differentiation. Additionally, we found that both nontreated and pembrolizumab-treated iTregs were suppressive. However, pembrolizumab-treated iTregs were relatively less suppressive in higher Treg ratios and failed to produce IL-10 compared with their nontreated counterparts. Different methods including transcriptomic analyses confirmed that the downregulation of FOXP3 was mediated by activating mTOR and STAT1 and inhibiting MAPK pathways, shifting the iTreg polarization in favor of Th1 and Th17 subsets. To confirm the role of mTOR activation, we found that rapamycin diminished the effect of pembrolizumab-mediated downregulation of FOXP3. Ingenuity pathway analysis revealed that pembrolizumab-treated iTregs showed upregulation of genes promoting DNA repair and immune cell trafficking, in addition to downregulation of genes supporting cellular assembly and organization. To our knowledge, this is the first study to show that pembrolizumab interferes with differentiation of human FOXP3(+) iTregs and to disclose some of the molecular pathways involved.

Flow cytometry and fluorescence-activated cell sorting have become invaluable tools to analyze and isolate specific cell populations in a wide range of biomedical research and clinical applications. In countless approaches worldwide, scientists are using single cell analyses to better understand the significance and variation within different cellular populations, and fluorescence-activated cell sorting has become a major technique for cell isolation in both basic and clinical research. However, majority of available cell sorters are pressurized, droplet-based systems, which apply significant environmental pressure and shear stress to cells during sorting. Recently, the flow cytometry community has become increasingly aware about the potential negative effects this could have on sorted cells and the term "sorter induced cell stress" (SICS) has been proposed. However, up to date only a limited number of studies have investigated the effects of cell sorting on cell viability and function. Therefore, solid data on the effects of sheath pressure and nozzle size on survival and function of sorted cells are surprisingly rare. With this in mind, we sorted "CD4+" T-cells and "live" cells from human peripheral blood mononuclear cells (PBMCs) at different sort conditions and analyzed their quality before and after sorting in a series of assays. Here we present our findings in reference to cell viability and cell proliferation following sorting on different instruments (BD FACSAria III SORP and BD FACSJazz), utilizing different nozzle sizes (70 to 100 μm) and sheath pressure settings (20 to 70 psi). The results show no significant differences in cell viability and proliferation after the different tested sort conditions, but rather differences between individual experiments. These findings are evaluated and their potential significance in cell sorting experiments is discussed.

Within the framework of a comprehensive limnological survey of the shallow urban lake Alte Donau in Vienna (Austria), the pelagic ciliate assemblage has been continuously investigated throughout the years 1995-2000. The application of a quantitative protargol stain (QPS) resulted in accurate data on ciliate species composition, as well as reliable abundance and biomass numbers. The main ciliate groups throughout the investigated period were identified as oligotrichs, prostomatids and small hymenostomes, thus composing the so-called Oligotrichetea a ubiquitous and typical ciliate community found also in many other comparable beta-to alpha-mesosaprobic pelagic environments. Significant seasonal variations in ciliate abundance and biomass occurred, revealing lowest numbers during autumn and winter. Despite the overall species composition being relatively unaltered during the investigated years, absolute ciliate numbers and biomasses were high at the beginning of the investigated period during the years of chemical RIPLOX-treatment and decreased by more than 50% in the last 2 years of the study. This decrease of ciliate numbers and biomass parallels thus the significant decrease of nutrients in the water body as a result of phosphorus precipitation in 1995 and 1996, followed by several restoration measures carried out during the years 1998-1999. Thus, lowest ciliate abundance and biomass occurred in the last year of restoration and slightly increased again with the re-colonization of macrophytes the year after.

Adaptive immune responses are severely affected by the aging process as reflected by an increased morbidity and mortality from infectious diseases and a low efficacy of vaccination in elderly persons. Age-related changes within the bone marrow and thymus lead to an impaired generation of new T and B cells severely compromising the maintenance of a diverse and balanced T and B cell repertoire in old age. The maintenance of a balanced T cell repertoire is further challenged by latent persistent infections, such as Cytomegalovirus. Understanding the mechanisms of age-related alterations of the adaptive immune response may help to facilitate the development of more efficient vaccines for elderly persons and to envisage strategies to overcome immunosenescence.

The continuous global increase in life expectancy represents a central challenge for our society and impacts public social security systems, families and individuals. One of the most striking changes that occur during normal human aging is immunosenescence, a progressive and overall diminution of immune functions that affect all cells and organs of the innate and adaptive immune system. As a hallmark of human aging, the progressive involution of the thymus leads to a disturbed balance and function of naïve, memory and effector T cells, thus promoting a latent pro-inflammatory status in the elderly. Together with chronic infections such as cytomegalovirus, that accumulate during life, this situation manifests in clinically relevant implications such as poor overall immune responses, decreased ability to control infectious disease and diminished response to vaccinations. Interestingly, this process parallels changes in the hormonal balance of aging subjects. In this review, we summarize recently published intriguing results from a very active and growing field of biomedical research and discuss some clinical consequences as well as possible ways of immune- and/or hormone-based interventions to delay or reverse immunosenescence.

The age-related decline in immune system functions is responsible for the increased prevalence of infectious diseases and the low efficacy of vaccination in elderly individuals. In particular, the number of peripheral naive T-cells declines throughout life and they exhibit severe functional defects at advanced age. However, we have recently identified a non-regulatory CD8+CD45RO+ CD25+ T-cell subset that occurs in a subgroup of healthy elderly individuals, who still exhibit an intact humoral immune response following influenza vaccination. Here, we demonstrate that CD8+CD45RO+CD25+ T-cells share phenotypic and functional characteristics with naive CD8+CD45RA+CD28+ T-cells from young individuals, despite their expression of CD45RO. CD8+CD45RO+ CD25+ T-cells also have long telomeres and upon antigenic challenge, they efficiently expand in vitro and differentiate into functional effector cells. The expanded population also maintains a diverse T-cell receptor repertoire. In conclusion, CD8+CD45RO+CD25+ T-cells from elderly individuals compensate for the loss of functional naive T-cells and may therefore be used as a marker of immunological competence in old age.

The continuous global increase in life expectancy represents a central challenge for our society and impacts public social security systems, families and individuals. One of the most striking changes that occur during normal human aging is immunosenescence, a progressive and overall diminution of immune functions that affect all cells and organs of the innate and adaptive immune system. As a hallmark of human aging, the progressive involution of the thymus leads to a disturbed balance and function of naive, memory and effector T cells, thus promoting a latent pro-inflammatory status in the elderly. Together with chronic infections such as cytomegalovirus, that accumulate during life, this situation manifests in clinically relevant implications such as poor overall immune responses, decreased ability to control infectious disease and diminished response to vaccinations. Interestingly, this process parallels changes in the hormonal balance of aging subjects. In this review, we summarize recently published intriguing results from a very active and growing field of biomedical research and discuss some clinical consequences as well as possible ways of immune-and/or hormone-based interventions to delay or reverse immunosenescence. Copyright (C) 2008 S. Karger AG, Basel

Already at initial phases of infection, HIV is coated with complement fragments. During the chronic phase, when HIV-specific IgGs appear, the virus circulates immune complexed with IgG and complement. Thus, we studied the interaction of dendritic cells (DCs) and DC-T cell cocultures with complement (C)-opsonized and C-IgG-opsonized HIV. HIV infection of monocyte-derived DCs and circulating BDCA-1-positive DCs was significantly reduced upon the presence of virus-specific but non-neutralizing IgGs. DCs exposed to C-Ig-HIV or IgG-opsonized HIV showed an impaired provirus formation and p24 production and a decreased transmission rate to autologous nonstimulated T cells upon migration along a chemokine gradient. This reduced infectivity was also observed in long-term experiments, when T cells were added delayed to DCs exposed to IgG-coated HIV without migration. Similar kinetics were seen when sera from HIV-1-infected individuals before and after seroconversion were used in infection assays. Both C- and C-IgG-opsonized HIV were captured and targeted to a tetraspanin-rich endosome in immature DCs, but differed with respect to MHC class II colocalization. The reduced infection by IgG-opsonized HIV is possibly due to interactions of virus-bound IgG with FcγRIIb expressed on DCs. Therefore, the intracellular fate and transmission of immune-complexed HIV seems to differ depending on time and opsonization pattern.

The public health of our society is challenged by a continuous increase in life expectancy. Hence, biomedical aging research is enjoying a steadily increasing popularity but also enlightens our understanding of age-related diseases by a number of striking results from basic research. One of the most striking changes that occurs during normal human aging is an overall diminution of immune functions, a phenomenon often termed immunosenescence. Starting from some highly exciting examples from basic immunological research, this article sheds light on which impact normal human aging has on several immune defence mechanisms. In addition, clinical consequences in view of Alzheimer's disease, immunogenicity of vaccines and autoimmune diseases are discussed.

Die stetig zunehmende Lebenserwartung in unserer Gesellschaft ist mit enormen medizinischen Herausforderungen verbunden. Die biomedizinische Alternsforschung erfreut sich somit wachsender Bedeutung und trägt mit zum Teil Aufsehen erregenden Ergebnissen maßgeblich zum Verständnis altersassoziierter Erkrankungen bei. Eine der wesentlichen altersbedingten körperlichen Veränderungen betrifft das Immunsystem, ein Phänomen das kollektiv als Immunseneszenz bezeichnet wird. Dieser Artikel beschreibt anhand einiger besonders aktueller Themen aus der immunologischen Grundlagenforschung wie das normale Altern zu Veränderungen in der menschlichen Immunabwehr führen kann. Weiterhin werden die sich daraus ergebenden klinischen Konsequenzen in Bezug auf die Alzheimer-Erkrankung, die Reaktion auf Impfungen und Autoimmunerkrankungen beleuchtet.

The length of telomeres is believed to critically influence cellular aging processes and disease development. In order to reliably monitor telomere length and the corresponding cellular telomerase activity by optimized procedures, either based on flow cytometry or quantitative PCR technique, we here propose three commonly used cell lines, HEK293, K562 and TCL1301 as standards. In this contribution, efficient methods to determine mean telomere length of eukaryotic chromosomal DNA and determination of the corresponding telomeras activity are outlined. In particular, wide-range standard curves for a precise assessment of telomere length of genomic DNA by quantitative PCR technique are presented, measures, which greatly simplify the evaluation of respective functional roles of telomeres when studying biological processes such as disease progression and aging.