Flow Cytometric Analysis of Human Antigen-Specific T-Cell Proliferation

Evaluation of the anticancer activities with various ligand substituents in Co(II/III)-picolyl phenolate derivatives: synthesis, characterization, DFT, DNA cleavage, and molecular docking studies

The reactions between 2-(pyridine-2-ylmethoxy)-benzaldehyde (L) and various primary amines furnish tridentate (L1 to L3) and tetradentate (L4) chelating ligands. The choice of different primary amines in the condensation reaction incorporates the chiral carbon atom in L2 and L3. A series of mononuclear cobalt(II) complexes, [CoII(L1)(Cl)2] (1), [CoII(L2)(Cl)2]·CH3CN (2), [CoII(L3)(Cl)2] (3), and [CoIII(L4)(N3)2] (4) are synthesized in the pure crystalline state from the resulting solution of cobalt(II) chloride and/or azide and respective ligand. The new ligands and cobalt complexes are characterized using spectral (UV-Vis, 1H-NMR, IR, and HRMS), cyclovoltammetric, and DFT studies. The structure of L1, L2, and all four cobalt complexes are determined by single X-ray crystallography. Cytotoxic activity of the compounds is evaluated using three different tissues of origin e.g., U-937 (histiocytic lymphoma), HEK293T (embryonic kidney), and A549 (lung carcinoma). The cobalt complexes are more active than the corresponding ligands against U-937 and HEK293T. The MTT assay demonstrates that the cobalt compounds are more effective anticancer agents against U-937 cancer cells than HEK293T and A549. The toxicity order, 1 (7.2 ± 0.3 μM) > 3 (11.4 ± 0.6 μM) > 2 (12 ± 0.1 μM) > 4 (29 ± 1 μM) is observed against U-937 cancer cells. All the compounds induce cell death through an apoptosis mechanism and all are ineffective against PBMCs. The mechanism of activity against U937 cancer cells involves caspase-3 activation and two different mitogen-activated protein kinases attesting the programmed cell death. Among the compounds, complexes 1, 2, and 3 show DNA cleavage activity both in oxidizing (H2O2) and reducing (GSH) environments. The mechanistic study reveals that singlet oxygen (1O2) is the major species involved in DNA cleavage. The absolute chemical hardness values of the ligands and 4 are relatively higher than 1, 2, and 3, which tacitly support the DNA cleavage experiment. The docking result indicates that the compounds under investigation strongly interact with DNA base pairs through a variety of interactions which attests successfully to the experimental results. A structure-activity relationship has been drawn to correlate the variation of antitumor activity with ligand conformations.

Anticancer activity, DNA binding and docking study of M(ii)-complexes (M = Zn, Cu and Ni) derived from a new pyrazine–thiazole ligand: synthesis, structure and DFT

A series of structurally related Zn(ii), Cu(ii) and Ni(ii) complexes of 4-(2-(2-(1-(pyrazin-2-yl)ethylidene)hydrazinyl)-thiazol-4-yl)-benzonitrile (PyztbH) have been synthesized and characterized by spectroscopy, single crystal X-ray crystallography and density functional theory (DFT).

Detection of Avian Antigen-Specific T Cells Induced by Viral Vaccines

Live attenuated viral vaccines are widely used in commercial poultry production, but the development of new effective inactivated/subunit vaccines is needed. Studies of avian antigen-specific T cells are primarily based on analyses ex vivo after activating the cells with recall antigen. There is a particular interest in developing robust high-throughput assays as chicken vaccine trials usually comprise many individuals. In many respects, the avian immune system differs from the mammalian, and T cell assessment protocols must be adjusted accordingly to account for, e.g., differences in leukocyte subsets.The carboxyfluorescein succinimidyl ester (CFSE) method described in this chapter has been adapted to chicken cells. In this test, cells of interest are stained with CFSE. The succinimidyl ester group covalently binds to cellular amines forming fluorescent conjugates that are retained in the cells even throughout division. This leads to daughter cells containing half the fluorescence of their parents. When lymphocytes are loaded with CFSE prior to ex vivo stimulation with specific antigen, the measurement of serial halving of its fluorescence by flow cytometry identifies the cells responding to the stimulation. This method has been successfully applied to studies of chicken antigen-specific T cells.

Current understanding of HIV-1 and T-cell adaptive immunity: progress to date

The cellular immune response to human immunodeficiency virus (HIV) has different components originating from both the adaptive and innate immune systems. HIV cleverly utilizes the host machinery to survive by its intricate nature of interaction with the host immune system. HIV evades the host immune system at innate ad adaptive, allows the pathogen to replicate and transmit from one host to another. Researchers have shown that HIV has multipronged effects especially on the adaptive immunity, with CD4(+) cells being the worst effect T-cell populations. Various analyses have revealed that, the exposure to HIV results in clonal expansion and excessive activation of the immune system. Also, an abnormal process of differentiation has been observed suggestive of an alteration and blocks in the maturation of various T-cell subsets. Additionally, HIV has shown to accelerate immunosenescence and exhaustion of the overtly activated T-cells. Apart from causing phenotypic changes, HIV has adverse effects on the functional aspect of the immune system, with evidences implicating it in the loss of the capacity of T-cells to secrete various antiviral cytokines and chemokines. However, there continues to be many aspects of the immune- pathogenesis of HIV that are still unknown and thus required further research in order to convert the malaise of HIV into a manageable epidemic.

Simultaneous analysis of p53 protein expression and cell proliferation in irradiated human lymphocytes by flow cytometry

P53 protein has an intrinsic role in modulating the cellular response against DNA radioinduced damages and has been pointed out as an indirect indicator of individual radiosensitivity. The rate of cell proliferation is also a parameter that has been related to tissue sensitivity to radiation. However, this feature is yet understudied. In this context, the aim of this work was to employ Flow Cytometry (FC) for simultaneously assessing of p53 protein expression levels together with cellular proliferation rate of irradiated human lymphocytes. From in vitro irradiated human blood samples, mononuclear cells were isolated and labeled with Carboxylfluorescein Diacetate Succinimidyl Ester (CFSE) prior to phytohaemagglutinin (PHA) stimulation in culture for 96 hours. Cells were also labeled with anti-p53 monoclonal antibody PE-conjugated in order to analyze either proliferation rate or p53 expression levels by FC. It was verified a reduction in the proliferation rate of irradiated lymphocytes and, in parallel, a rise in the p53 expression levels, similar for quiescent and proliferating lymphocytes. The results emphasize the importance of the use of CFSE-stained lymphocytes in assays associated to proliferation rate and the use of this methodology in several studies, such as for evaluating individual radiosensitivity.

In vitro assessment of the feline cell-mediated immune response against feline panleukopeniavirus, calicivirus and felid herpesvirus 1 using 5-bromo-2'-deoxyuridine labeling

In this study an in vitro assay was optimized to detect feline proliferating lymphocytes as an assessment for the cell-mediated immune response. For this purpose, 5-bromo-2′-deoxyuridine (BrdU) labeling was chosen because of its sensitivity and the possibility of further characterization of proliferating cells. The assay was optimized by selecting the best batch and concentration of fetal bovine serum, β-mercaptoethanol concentration, cell density, BrdU incubation time and antigen presenting cell type. Cats were vaccinated with the attenuated Nobivac vaccine Tricat and the peripheral blood lymphocyte proliferation responses were quantified upon in vitro restimulation with inactivated and infectious feline panleukopenia virus (FPV), feline calicivirus (FCV) and felid herpesvirus 1 (FeHV-1). Proliferation signals were detected with inactivated FeHV-1 in the CD8⁺ but not in the CD8⁻ T lymphocyte population, with inactivated FCV and FPV in both CD8⁻ and CD8⁺ T lymphocyte populations. Restimulation with infectious FCV caused significant proliferation in the CD8⁻ T lymphocyte population only while infectious FPV and FeHV-1 seemed to suppress lymphocyte proliferation in both T cell populations. Additional IFN-γ quantification in the culture supernatant revealed a large correlation between the proliferation signals and IFN-γ production, indicating that BrdU labeling is a very reliable technique to assess and characterize feline lymphoproliferative responses to viral antigens in vitro.

Immune reconstitution in recipients of photodepleted HLA-identical sibling donor stem cell transplantations: T cell subset frequencies predict outcome

We evaluated an ex vivo photodepletion (PD) technique to selectively deplete graft-versus-host disease (GVHD) alloreacting T cells given to 24 human leukocyte antigen (HLA)-identical sibling stem cell transplantation (SCT) recipients. Donor lymphocytes were activated by 72-hour exposure to irradiated in vitro expanded recipient T lymphocytes and pulsed with a TH9402 photosensitizer. Alloactivated T cells preferentially retaining the photosensitizer were eliminated by light exposure. The PD product showed an inverted CD4(+)/CD8(+) ratio with greatest depletion occurring in the CD4(+) naive and central memory populations. In contrast, the CD8(+) naive and effector cells were relatively conserved, reflecting the differential extrusion of TH9402 by T cell subsets. Cytomegalovirus reactive T cells were reduced in the PD product and in recipient blood 100 days after SCT when compared with contemporaneous HLA-identical sibling donor T cell-depleted SCT recipients. Although PD SCT recipients experienced similar absolute lymphocyte counts during the first 100 days after SCT, they achieved 100% donor T cell chimerism more rapidly and had higher CD8(+) naive T cell counts early after SCT. SCT recipients of PD products with the lowest CD4 central memory content had the highest risk of developing chronic GVHD (cGVHD) (P = .04) and a poorer survival (P = .03). Although the persistence of CD8(+) naive T cells may have contributed to important antileukemia responses resulting in a relatively low relapse rate, our findings emphasize the role of donor memory T cells and CD4 cells in establishing immune competence post-SCT. Although PD is associated with excellent outcomes in the haploidentical setting, the low frequency of alloactivations in HLA-matched pairs makes the PD approach used by our group for allodepletion in HLA-matched sibling transplantations an inefficient technique.

Good cell, bad cell: flow cytometry reveals T-cell subsets important in HIV disease

Flow cytometry is a key technology in the study of HIV disease. In this article, we review various cellular markers that can be measured in the setting of pathogenesis or vaccination studies, including markers of activation, differentiation, senescence, immune suppression, and function. In addition, we discuss important considerations for making these measurements. Finally, we examine how flow cytometry studies have taught researchers about the disease process, and the potential for flow cytometry technology to guide treatment decisions and evaluate vaccine candidates in the future.

Flow cytometric assessment of antigen-specific proliferation in peripheral chicken T cells by CFSE dilution

Carboxyfluorescein succinimidyl ester (CFSE) dilution is a well established method for analysis of dividing cells by flow cytometry. In other species the method has been extensively used in the study of antigen-specific T cells. The purpose of this study was to apply the method to chicken peripheral mononuclear blood cells (PBMC) and to evaluate and optimize its performance in relation to detection of vaccine-induced chicken T cells specific for Newcastle disease virus (NDV). The method was based on analysis of CFSE dilution upon ex vivo recall stimulation with whole vaccine antigen. Analysis of proliferation was combined with the use of monoclonal antibodies directed against the lymphocyte surface markers CD4 and CD8 in order to phenotype the responding cells. Problems with nonspecific background proliferation especially in the CD8 compartment were significantly reduced by replacing medium containing fetal calf serum with serum-free medium. It was rendered probable that antigen-specific cellular immunity can be assessed by this method as NDV-vaccinated chickens showed a significantly higher proliferative capacity than age-matched naïve controls. Furthermore it was shown that the recall stimulation lead to a proliferative response in T cells expressing αβ-type TCRs but also those expressing the γδ-type. In summary, the method was found challenging but nevertheless useful to quantify the proliferative response of chicken antigen-specific T cells. Further investigations though, are needed in order to prove what cell subsets are true antigen-specific responders and what cells are bystander activated. Nevertheless, the method is expected to be a valuable tool to evaluate and quantify vaccine responses to current and new chicken vaccines in the future.

Regulatory T-cell depletion does not prevent emergence of new CD25+ FOXP3+ lymphocytes after antigen stimulation in culture

BACKGROUND

The removal of human regulatory T (T(reg)) cells from a cellular product prior to the induction of a T-cell response has the potential to boost the total yield of antigen (Ag)-specific CD4(+) and CD8(+) T cells.

METHODS

We examined the effect of this manipulation on the generation of human anti-cytomegalovirus (CMV) T-cell responses. Furthermore, we examined the clonotypic composition of Ag-specific CD4(+)FOXP3(+) and CD4(+)FOXP3(-) T cells.

RESULTS

We found that the immunomagnetic depletion of CD25(+) cells had an unpredictable effect on outcome, with total yields of CMV-specific T cells either increasing or decreasing after the removal of these cells. The depletion of CD25(+) cells both removed a proportion of Ag-specific T cells and failed to eliminate a substantial population of T(reg) cells. Furthermore, using a novel T-cell receptor clonotyping technique, we found that Ag recognition induces the expression of FOXP3 in a proportion of specific T cells; these FOXP3-expressing Ag-specific CD4(+) and CD8(+) T cells were no longer capable of producing inflammatory cytokines.

DISCUSSION

The depletion of CD25(+) cells from the starting population has a variable effect on the total yield of Ag-specific T cells, a proportion of which invariably acquire FOXP3 expression and lose effector function.