Measurement of apoptotic cells in peripheral blood

Red Blood Cell Cryopreservation with Minimal Post-Thaw Lysis Enabled by a Synergistic Combination of a Cryoprotecting Polyampholyte with DMSO/Trehalose

From trauma wards to chemotherapy, red blood cells are essential in modern medicine. Current methods to bank red blood cells typically use glycerol (40 wt %) as a cryoprotective agent. Although highly effective, the deglycerolization process, post-thaw, is time-consuming and results in some loss of red blood cells during the washing procedures. Here, we demonstrate that a polyampholyte, a macromolecular cryoprotectant, synergistically enhances ovine red blood cell cryopreservation in a mixed cryoprotectant system. Screening of DMSO and trehalose mixtures identified optimized conditions, where cytotoxicity was minimized but cryoprotective benefit maximized. Supplementation with polyampholyte allowed 97% post-thaw recovery (3% hemolysis), even under extremely challenging slow-freezing and -thawing conditions. Post-thaw washing of the cryoprotectants was tolerated by the cells, which is crucial for any application, and the optimized mixture could be applied directly to cells, causing no hemolysis after 1 h of exposure. The procedure was also scaled to use blood bags, showing utility on a scale relevant for application. Flow cytometry and adenosine triphosphate assays confirmed the integrity of the blood cells post-thaw. Microscopy confirmed intact red blood cells were recovered but with some shrinkage, suggesting that optimization of post-thaw washing could further improve this method. These results show that macromolecular cryoprotectants can provide synergistic benefit, alongside small molecule cryoprotectants, for the storage of essential cell types, as well as potential practical benefits in terms of processing/handling.

Hhex Directly Represses BIM-Dependent Apoptosis to Promote NK Cell Development and Maintenance

Hhex encodes a homeobox transcriptional regulator important for embryonic development and hematopoiesis. Hhex is highly expressed in NK cells, and its germline deletion results in significant defects in lymphoid development, including NK cells. To determine if Hhex is intrinsically required throughout NK cell development or for NK cell function, we generate mice that specifically lack Hhex in NK cells. NK cell frequency is dramatically reduced, while NK cell differentiation, IL-15 responsiveness, and function at the cellular level remain largely normal in the absence of Hhex. Increased IL-15 availability fails to fully reverse NK lymphopenia following conditional Hhex deletion, suggesting that Hhex regulates developmental pathways extrinsic to those dependent on IL-15. Gene expression and functional genetic approaches reveal that Hhex regulates NK cell survival by directly binding Bcl2l11 (Bim) and repressing expression of this key apoptotic mediator. These data implicate Hhex as a transcriptional regulator of NK cell homeostasis and immunity.

Improved detection of diffuse large B-cell lymphoma by flow cytometric immunophenotyping-Effect of tissue disaggregation method

BACKGROUND

Flow cytometric immunophenotyping (FCI) is recognized as a rapid, sensitive, and accurate method for diagnosis of B-cell lymphomas. We observed that FCI failed to identify the clonal B-cell population in several cases of large B-cell lymphoma (DLBCL) when tissue samples were prepared by a commercially available mechanical tissue disaggregation method. We tested a manual tissue disaggregation method and compared it with the mechanical method.

METHODS

FCI findings from 51 cases of DLBCL processed with the mechanical tissue disaggregation method, 27 cases processed using the manual method, and 15 cases processed using a combination of both methods were compared. The histological and immunohistochemical findings in each case were reviewed.

RESULTS

FCI detected a clonal B-cell population in 88.9% of cases processed by the manual tissue disaggregation method, 66.7% of cases processed by a combination of the manual and mechanical disaggregation methods, and in 62.7% of cases processed solely by the mechanical tissue disaggregation method (P < 0.01 Fisher exact). Manual processing yielded positive FCI results in 81.8% of the nodal tissue samples and 93.8% of the extra-nodal tissue samples, whereas mechanical disaggregation was particularly inefficient in preserving large lymphoma cells from extra-nodal tissue: 71.4% of the nodal and 56.8% of the extra-nodal tissue samples processed by the mechanical method showed clonal B-cells by flow cytometry (P < 0.006, Fisher exact).

CONCLUSIONS

The diagnostic yield of FCI in DLBCL can be significantly improved by utilizing a manual disaggregation method, particularly in extra-nodal tissue samples. © 2015 International Clinical Cytometry Society.

Soluble TRAIL gene and actinomycin D synergistically suppressed multiple metastasis of TRAIL-resistant colon cancer in the liver

Metastatic liver tumors are highly malignant and refractory to conventional therapies. TRAIL-resistant CT-26 cells underwent apoptosis in vitro in the presence of both recombinant TRAIL (rTRAIL) and a suboptimal dose of actinomycin D (ACD). Co-administration of soluble TRAIL (sTRAIL) gene and ACD suppressed the metastatic liver tumors of CT-26, significantly inducing apoptosis in the tumors, while such effects were not demonstrated in mice that received either the sTRAIL gene or ACD alone. The gene therapy of sTRAIL with a suboptimal dose of an anticancer drug is a new strategy for treatment of multiple liver metastasis.

Relationship between p53 status and 5-fluorouracil sensitivity in 3 cell lines

Mouse lymphoma L5178Ytk+/- (MOLY) cells and human lymphoblastoid TK6 and WTK-1 cells are widely used to detect mutagens in vitro. MOLY and WTK-1 cells have a p53 mutation, while TK6 cells, which were derived from the same parental line as WTK-1 cells, do not. In this study, we tested the clastogen 5-fluorouracil (5-FU) in the Tk assay and the in vitro micronucleus (MN) assay in MOLY, TK6, and WTK-1 cells to clarify whether differential responses were related to p53 gene status. We also determined the effect of 5-FU on the frequency of apoptotic cells and on cell cycle distribution in each cell line. Furthermore, we measured the activity of the 5-FU metabolizing enzymes (thymidylate synthetase (TS), dihydrouracil dehydrogenase (DPD), orotate phosphoribosyl transferase (OPRT), and thymidine phosphorylase (TP)) in each cell line. We treated MOLY cells with 1.0-8.0 microg/mL 5-FU for 3 h and TK6 and WTK-1 cells with 1.56-25 and 3.13-50 microg/mL, respectively, for 4 h. In MOLY cells, the mutation frequency (MF) and MN frequency increased. In WTK-1 cells, the MN frequency but not the MF increased. In TK6 cells, neither the MF nor the MN frequency increased. Furthermore, the IC50 of 5-FU was lower in MOLY cells than in the human cells. The response to 5-FU treatment differed in other ways as well. At the same level of cytotoxicity, the frequency of apoptotic cell was highest in TK6 cells. The cell cycle was delayed just after treatment in MOLY cells while the delay appeared 24 h later in TK6 and WTK-1 cells. Nothing in our analysis, however, revealed marked differences between the cell lines that could account for the severe cytotoxic and mutagenic responses that 5-FU elicited only in MOLY cells. 5-FU is phosphorylated by OPRT and TP and detoxified by DPD. MOLY cells have higher OPRT activity and markedly lower DPD and TP activity than TK6 and WTK-1 cells. The content of TS, however, the target enzyme of 5-FU, was similar in all cell lines, suggesting that 5-FU was more readily phosphorylated and less readily detoxified in MOLY cells than in TK6 and WTK-1 cells. MOLY cells were more sensitive to 5-FU than WTK-1 cells even though both have a mutated p53 gene, suggesting that the different responses to 5-FU were due to differences in 5-FU metabolism rather than the p53 status.

Oxaliplatin (L-OHP) treatment of human myeloma cells induces in vitro growth inhibition and apoptotic cell death

Oxaliplatin (L-OHP), a diaminocyclohexane platinum derivative, is an active and well tolerated anticancer drug which is presently used in the treatment of gastrointestinal tumours. Since the efficacy of L-OHP in the treatment of multiple myeloma (MM) has not yet been evaluated, we studied the antiproliferative activity of this compound in vitro in a panel of MM cell lines (XG1, XG1a, U266 and IM-9). We found that L-OHP inhibited the growth of MM cells at therapeutically achievable concentrations (IC(50): 5-10 microM after 24 h of exposure) and was more active than Cisplatin (CDDP) or Carboplatin (CBDCA). The activity of L-OHP was apparently not affected by interleukin-6 (IL-6), the major growth and survival factor of MM cells. We also found that L-OHP induced apoptotic cell death. We demonstrated that the combination of L-OHP with Dexamethasone (Dex) resulted in the enhancement of the anti-myeloma effects. L-OHP and Dex both induced poly adenosine diphosphate (ADP)-ribose polymerase (PARP) cleavage and this induction was enhanced by the combined treatment. L-OHP-induced apoptosis correlated with caspase-3 cleavage, but this correlation could not be demonstrated in Dex-treated cells. Taken together, these in vitro results provide a rationale for the experimental use of L-OHP in the treatment of MM patients and suggest therapeutic combinations of potential value.

Insulin-like growth factor I receptor is downregulated after alveolarization in an apoptotic fibroblast subset

After alveolar formation, >20% of interstitial lung fibroblasts undergo apoptosis, a process that is of critical importance for normal lung maturation. The immature lung contains two morphologically distinct fibroblast populations, lipid-filled interstitial fibroblasts (LIF) and non-LIF (NLIF), which differ with respect to contractile protein content, proliferative capacity, and expression of mRNAs for fibronectin and types I and III collagen, but not tropoelastin. After alveolarization, apoptosis occurs in only one fibroblast population, the LIF. Using flow cytometry to analyze fibroblasts stained with a lipophilic, fluorescent dye, we identified a subset, designated LIF(-), that contained fewer lipid droplets. Unlike LIF that retain lipid, LIF(+), the LIF(-) do not undergo apoptosis after alveolarization. In LIF(+), apoptosis was correlated with downregulation of insulin-like growth factor I receptor (IGF-IR) mRNA and cell surface protein expression. Treatment with anti-IGF-IR decreased total lung fibroblast survival (P = 0.05) as did treatment with the phosphatidylinositol 3-kinase inhibitor LY-294002 and the ras-raf-mitogen-activated protein kinase inhibitor PD-98059 (P < 0.002), which block IGF-I/insulin receptor survival pathways. These observations implicate downregulation of IGF-IR expression in fibroblast apoptosis after alveolar formation.

The role of the CD4 receptor versus HIV coreceptors in envelope-mediated apoptosis in peripheral blood mononuclear cells

We examined the role of CD4, CXCR4, and CCR5 in HIV envelope-mediated apoptosis by measuring the response of activated PBMCs to recombinant envelope proteins derived from CXCR4- and CCR5-utilizing viruses. Apoptosis of T cells was assessed by annexin-V staining and TdT-mediated dUTP-biotin nick-end labeling. Treatment of CCR5Delta32 homozygote PBMCs with a CCR5-specific envelope induced apoptosis in T cells, demonstrating that envelope--CD4 interactions are sufficient to induce apoptosis. However, a CXCR4-specific envelope induced higher levels of apoptosis than a CCR5-specific envelope, suggesting that envelope-mediated apoptosis can be enhanced by envelope--CXCR4 interactions. We conclude that envelope can induce apoptosis in T cells independently of the coreceptor specificity of a given envelope, or the expression profile of CXCR4 or CCR5 on a target cell. However, envelope--coreceptor interactions, and in particular, envelope--CXCR4 interactions, can contribute to this process.

Immunophenotyping large B-cell lymphomas. Flow cytometric pitfalls and pathologic correlation

Large cell lymphomas often challenge the diagnostic flow cytometrist. The purposes of this study were to improve our protocols for diagnosing large cell lymphomas and to correlate flow cytometric (FC) data with demographic and histologic features. We identified 63 cases of large B-cell lymphoma between January 1, 1995, and July 30, 1999, and reviewed the diagnostic slides and FC light scatter and staining patterns. The 51 lymphomas with adequate material for systemic review fell into 2 light scatter patterns: "clear cut," with large abnormal cells (high forward scatter relative to normal lymphocytes), 17 cases (33%); and "complex," 34 cases (67%). Clear-cut cases were more mitotically active (average of 42 vs 25 per 10 high-power fields), with higher cellularity. Apoptosis, geographic necrosis, and sclerosis were present histologically in many cases, regardless of FC findings. We conclude that morphologic features of large cell lymphomas do not predict which cases will be difficult to diagnose by FC. Gating strategies can be critical to improve the diagnostic yield.

Apoptosis induction and cell cycle perturbation in established cell lines by peroxysomicine A1 (T-514)

Peroxysomicine A1, a novel potential anticancer compound induced cell death in established cell lines and in a primary culture of rat neonatal cardiomyocytes. Non-transformed cells are less sensitive to the compound than transformed cell lines. Fluorescent microscopy of dying cells stained with DNA-specific dyes revealed chromatin condensation and nuclear fragmentation as well as membrane blebbing characteristic of apoptosis. Flow cytometry of cells treated with peroxysomicine A1, demonstrated appearance of cells containing less than 2C DNA, that indicated degradation of nuclear DNA, another hallmark of apoptotic cell death. Z-VAD, a nonspecific caspase inhibitor, prevented DNA fragmentation but not cell death registered by permeabilization of cell outer membrane. Peroxysomicine A1 also inhibited proliferation of various cell lines. Flow cytometry analysis showed significant accumulation of dividing cells in G2/M phases of cell cycle indicating, most likely delay in G2. These results provide initial insight into the mechanisms of action of peroxysomicine A1 and suggest that peroxysomicine A1 is a potent inhibitor of cell proliferation and inducer of apoptosis and may be a useful antineoplastic chemotherapeutic agent.

Immunophenotypes in adult acute lymphocytic leukemia. Role of flow cytometry in diagnosis and monitoring of disease

Flow cytometry has revolutionized the study of hematopoietic cells. Immunophenotyping by multiparameter flow cytometry supplements conventional morphologic diagnosis by providing information on cell lineage and differentiation in ALL and helps monitor disease by improving sensitivity in detecting minimal residual disease. The use of multiple MoAbs and multicolor study by flow cytometry has revealed heterogeneity among ALL and mixed-lineage acute leukemia, which are assigned to the same diagnostic categories by morphology. As technology has improved, clinical and research applications of flow cytometry have expanded to include evaluation of nuclear markers, oncogene proteins, apoptosis, cytokine receptors, and drug resistance. Expanded identification of MoAbs against leukemia-specific markers and the use of QFCM be a significant in managing patients with ALL in the future. In addition, flow cytometry and flow cytometric sorting will be combined more and more with other technologies, such as molecular probing or fluorescence in situ hybridization (FISH). The sorting of rare malignant cells based on immunophenotype and subsequent confirmation by PCR or FISH has already been proven feasible. Ultimately, it is hoped that further definition of subgroups of ALL by immunophenotyping using prognostically significant markers and the use of hybrid technologies of flow cytometry and molecular analysis or cytogenetics will improve treatment strategies for patients with ALL.

Growth inhibition and synergistic induction of apoptosis by zoledronate and dexamethasone in human myeloma cell lines

Bisphosphonates (BPs) are commonly used in the treatment of myeloma-associated osteolytic lesions. Recent reports have suggested that BPs may also exert direct antitumor effects on myeloma cells. Here, we show that the treatment of myeloma cell lines with the combination of the potent BP zoledronate and dexamethasone inhibits cell growth and synergistically induces apoptotic cell death, providing a rationale for potential applications in vivo.

Apoptosis. Basic concepts and implications in coronary artery disease

Apoptosis is an active form of cell death that is intricately regulated and distinct from necrosis. Data suggest that apoptosis may play a role in the pathophysiology of coronary atherosclerotic disease. Anatomic evidence of apoptosis has been observed in coronary atherosclerosis, restenosis, and transplant arteriopathy, accompanied by an increase in biochemical and genetic markers of apoptosis. Vasoactive substances such as nitric oxide and angiotensin II also regulate vascular smooth muscle cell apoptosis; vasodilating factors may induce apoptosis, whereas vasoconstricting factors may inhibit apoptosis. The aim of this article is to review key points regarding the detection of apoptosis, its regulation, and its possible role in the pathogenesis of coronary artery disease.

Mapping of HIV-1 determinants of apoptosis in infected T cells

HIV-1 infection leads to death of CD4(+) T cells in vivo and in vitro, although the mechanisms of this cell death are not well defined. We used flow cytometry to concurrently analyze infection and apoptosis of the CD4(+) CEM T cell line and human peripheral blood mononuclear cells (PBMC). Surprisingly, T cells productively infected with HIV-1 IIIB showed less apoptosis than control, uninfected T cells. This relative paucity of apoptosis was a characteristic of IIIB, since a large number of cells infected with the viral clone, HIV-1 NL4-3, were apoptotic. The nef, vpr, and vpu gene products were not responsible for apoptosis of NL4-3-infected cells, since NL4-3DeltaVprDeltaVpuDeltaNef and HXB-2 (a nef, vpr, and vpu triple mutant derived from IIIB) also killed infected cells. Moreover, only IIIB-infected cells showed a resistance to background levels of apoptosis. Thus, the apoptotic (and antiapoptotic) properties of HIV-1 do not map solely to mutations in nef, vpr, or vpu. We postulate that, in vivo, HIV variants that do not induce rapid apoptosis in the cells they infect may have a selective advantage.

Comparison of seven quantitative assays to assess lymphocyte cell death during HIV infection: measurement of induced apoptosis in anti-Fas-treated Jurkat cells and spontaneous apoptosis in peripheral blood mononuclear cells from children infected with HIV

The study of apoptosis in relation to various human disease states, particularly HIV infection, has seen a tremendous increase in activity. In this article, values obtained by seven different assays, designed to quantify apoptosis and applicable to the study of HIV infection, are compared in two cell systems: (1) stimulus-induced apoptosis in Jurkat cells treated with anti-Fas antibody and (2) spontaneous apoptosis in PBMCs isolated from HIV-infected children. The methods used included measurement of cells with subdiploid DNA content, labeling of DNA strand breaks by the TUNEL reaction, annexin V surface labeling for the detection of exposed phosphatidylserine, cytoplasmic antigen labeling with the apoptosis-specific antibody Apo 2.7, detection of changes in flow cytometric light-scattering properties, trypan blue dye exclusion by light microscopy, and detection of changes in cellular chromatin by fluorescence microscopy. These methods produced well-correlated values in the Jurkat system, whereas the same set of methods produced more discrepant values in the PBMC analyses, especially in those patients with low CD4 counts. Specifically, our results showed that the trypan blue test was unacceptable for quantification of apoptosis during HIV infection, whereas TUNEL, of all the methods tested, showed excellent overall correlation in both cell systems, was highly specific, and matched microscopic observation of the cells. Although many of the methods were suited to the study of a homogeneous cell line, caution must be exercised when examining cell death in a heterogeneous cell mixture from an HIV-infected individual.

Anti-Estrogens Induce Apoptosis of Multiple Myeloma Cells

Previous studies have suggested that multiple myeloma (MM) cells express estrogen receptors (ER). In the present study, we characterized the effects of estrogen agonists and antagonists (anti-estrogens [AE]) on growth of MM cell lines and MM patient cells. In addition to antagonizing estrogen binding to ER, AE can trigger apoptosis. Hence, we also determined whether estrogens or AE altered MM cell survival. Immunoblotting showed that ER- is expressed in 4 of 5 MM cell lines (ARH-77, RPMI 8226, S6B45, and U266, but not OCI-My-5 cells), as well as in freshly isolated MM cells from 3 of 3 patients. 17β-estradiol (E2) did not significantly alter proliferation of MM cell lines or MM patient cells. In contrast, two structurally distinct AE, tamoxifen (TAM) and ICI 182,780 (ICI), significantly inhibited the proliferation of all 5 MM cell lines and MM cells from 2 of 2 patients (IC50, 2 to 4 μmol/L). Proliferation of these cell lines was also inhibited by the hydroxylated TAM derivative, 4-hydroxytamoxifen (4HTAM), although this derivative was less potent than TAM (IC50, 3 to 25 μmol/L). In contrast, the dehalogenated TAM derivative toremifene (TOR) did not inhibit MM cell proliferation. We next examined the effects of these agents on MM cell survival. TAM, ICI, and, to a lesser extent, 4HTAM and TOR triggered apoptosis in both ER-–positive as well as ER-–negative MM cell lines and patient MM cells, evidenced both by fluorescence-activated cell sorting (FACS) analysis using propidium iodide staining and the TUNEL assay. TAM-induced growth inhibition and apoptosis of ER-–positive S6B45 MM cells was not blocked by coculture with excess E2. TAM-induced apoptosis of S6B45 MM cells was also unaffected by addition of exogenous interleukin-6. Importantly, both the inhibition of MM cell proliferation and the induction of MM cell apoptosis were achieved at concentrations of TAM (0.5 and 5.0 μmol/L) that did not significantly alter in vitro growth of normal hematopoietic progenitor cells. Similar plasma levels of TAM have been achieved using high-dose oral TAM therapy, with an acceptable toxicity profile. These studies therefore provide the rationale for trials to define the utility of AE therapy in MM.

© 1998 by The American Society of Hematology.

Anti-Estrogens Induce Apoptosis of Multiple Myeloma Cells

Previous studies have suggested that multiple myeloma (MM) cells express estrogen receptors (ER). In the present study, we characterized the effects of estrogen agonists and antagonists (anti-estrogens [AE]) on growth of MM cell lines and MM patient cells. In addition to antagonizing estrogen binding to ER, AE can trigger apoptosis. Hence, we also determined whether estrogens or AE altered MM cell survival. Immunoblotting showed that ER- is expressed in 4 of 5 MM cell lines (ARH-77, RPMI 8226, S6B45, and U266, but not OCI-My-5 cells), as well as in freshly isolated MM cells from 3 of 3 patients. 17β-estradiol (E2) did not significantly alter proliferation of MM cell lines or MM patient cells. In contrast, two structurally distinct AE, tamoxifen (TAM) and ICI 182,780 (ICI), significantly inhibited the proliferation of all 5 MM cell lines and MM cells from 2 of 2 patients (IC50, 2 to 4 μmol/L). Proliferation of these cell lines was also inhibited by the hydroxylated TAM derivative, 4-hydroxytamoxifen (4HTAM), although this derivative was less potent than TAM (IC50, 3 to 25 μmol/L). In contrast, the dehalogenated TAM derivative toremifene (TOR) did not inhibit MM cell proliferation. We next examined the effects of these agents on MM cell survival. TAM, ICI, and, to a lesser extent, 4HTAM and TOR triggered apoptosis in both ER-–positive as well as ER-–negative MM cell lines and patient MM cells, evidenced both by fluorescence-activated cell sorting (FACS) analysis using propidium iodide staining and the TUNEL assay. TAM-induced growth inhibition and apoptosis of ER-–positive S6B45 MM cells was not blocked by coculture with excess E2. TAM-induced apoptosis of S6B45 MM cells was also unaffected by addition of exogenous interleukin-6. Importantly, both the inhibition of MM cell proliferation and the induction of MM cell apoptosis were achieved at concentrations of TAM (0.5 and 5.0 μmol/L) that did not significantly alter in vitro growth of normal hematopoietic progenitor cells. Similar plasma levels of TAM have been achieved using high-dose oral TAM therapy, with an acceptable toxicity profile. These studies therefore provide the rationale for trials to define the utility of AE therapy in MM.

© 1998 by The American Society of Hematology.

Death of Bystander Cells by a Novel Pathway Involving Early Mitochondrial Damage in Human Immunodeficiency Virus–Related Lymphadenopathy

Destruction of immune cells in peripheral lymphoid tissues plays presumably a pivotal role in acquired immune deficiency syndrome pathogenesis. We found that cell suspensions obtained from lymph nodes of eight human immunodeficiency virus (HIV)-infected individuals contained variable proportions (2.1% to 18.3%, median 11.2%) of dead lymphocytes permeable to supravital dyes, represented by CD4+, CD8+, and B cells. The frequency of dead cells correlated directly (R = 0.847) with the amount of HIV provirus in the cell populations, and HIV provirus was enriched in the dead cell fractions. Similar proportions of dead cells were observed in cell suspensions from lymphadenopathic lymph nodes of HIV− donors, but not from small resting HIV− lymph nodes. Electron microscopic and flow cytometric analyses revealed that most dead cells from HIV+ lymph nodes lacked internucleosomal DNA fragmentation but displayed combined features of apoptosis and necrosis, eg, chromatin condensation and mitochondrial swelling. Cells with similar morphology were readily identified in lymph node tissue sections, and marked mitochondrial swelling could be occasionally observed in cells with otherwise normal morphology. Our findings have two major implications. One is that the in vivo cell death in HIV-infected lymph nodes occurs predominantly through a novel pathway, related to but distinct from classical apoptosis and characterised by early and severe mitochondrial damage. The second implication is that HIV-related lymphadenopathy is accompanied in vivo by massive destruction of uninfected lymph node cells. Comparable levels of cell death were observed in other inflammatory lymphadenopathies not related to HIV; however, the uniquely endless and generalized nature of HIV lymphadenopathy might render this “inflammatory” cell destruction a powerful pathogenetic mechanism, accounting for the progressive disruption and depletion of lymphoid tissues seen in HIV infection.

Death of Bystander Cells by a Novel Pathway Involving Early Mitochondrial Damage in Human Immunodeficiency Virus–Related Lymphadenopathy

Destruction of immune cells in peripheral lymphoid tissues plays presumably a pivotal role in acquired immune deficiency syndrome pathogenesis. We found that cell suspensions obtained from lymph nodes of eight human immunodeficiency virus (HIV)-infected individuals contained variable proportions (2.1% to 18.3%, median 11.2%) of dead lymphocytes permeable to supravital dyes, represented by CD4+, CD8+, and B cells. The frequency of dead cells correlated directly (R = 0.847) with the amount of HIV provirus in the cell populations, and HIV provirus was enriched in the dead cell fractions. Similar proportions of dead cells were observed in cell suspensions from lymphadenopathic lymph nodes of HIV− donors, but not from small resting HIV− lymph nodes. Electron microscopic and flow cytometric analyses revealed that most dead cells from HIV+ lymph nodes lacked internucleosomal DNA fragmentation but displayed combined features of apoptosis and necrosis, eg, chromatin condensation and mitochondrial swelling. Cells with similar morphology were readily identified in lymph node tissue sections, and marked mitochondrial swelling could be occasionally observed in cells with otherwise normal morphology. Our findings have two major implications. One is that the in vivo cell death in HIV-infected lymph nodes occurs predominantly through a novel pathway, related to but distinct from classical apoptosis and characterised by early and severe mitochondrial damage. The second implication is that HIV-related lymphadenopathy is accompanied in vivo by massive destruction of uninfected lymph node cells. Comparable levels of cell death were observed in other inflammatory lymphadenopathies not related to HIV; however, the uniquely endless and generalized nature of HIV lymphadenopathy might render this “inflammatory” cell destruction a powerful pathogenetic mechanism, accounting for the progressive disruption and depletion of lymphoid tissues seen in HIV infection.

Combined Hoechst 33342 and merocyanine 540 staining to examine murine B cell cycle stage, viability and apoptosis

A procedure is described for the dual staining of lymphocytes with Hoechst 33342 (Ho342) to examine cell cycle position, and merocyanine 540 (MC540) that allows for the analysis of cells entering the early stages of apoptosis. Ho342 is a DNA specific dye and MC540 detects membrane phospholipid domain changes, some of which are associated with apoptotic cells. Flow analysis of B cells dually stained with Ho342 and MC540 allows for the discrimination of five distinct subpopulations. Two of these subpopulations represent viable, MC540 negative/dull cells with either 2n or 4n DNA. As 2n and 4n DNA B cells become MC540 bright they move into two distinct subpopulations representing cells entering and progressing through the early stages of apoptosis. As the apoptotic, MC540 bright cells move into the latter stages of apoptosis, they localize into a fifth subpopulation displaying reduced staining with Ho342 indicative of late stage apoptotic cells in the process of fragmenting their DNA. This experimental approach enables the characterization of lymphocyte populations for percentages of viable, early apoptotic, and late apoptotic cells. The cells are not fixed during this procedure, and since both dyes are viable dyes there is an additional opportunity to obtain sorted cells from any of the defined subpopulations for reculturing and functional analysis.

Apoptotic cell death, detected ex vivo in peripheral blood lymphocytes of HIV-1 infected persons

In HIV-1 infection the ongoing depletion of CD4+ T-lymphocytes is believed, to a large extent, to be due to apoptosis. Until now quantitative information about in vivo apoptosis of lymphocytes in HIV-patients is scarce because of the very nature of the apoptotic process. Successful detection of apoptosis ex vivo requires the recognition of the initial phase of this process, because at a later stage the cells may not remain any longer in the circulation. We measured quantitatively the amount of early apoptotic peripheral blood lymphocytes directly ex vivo in HIV-1 infected patients using a recently described flow cytometric assay. With this method we observed in an unselected heterogenous group of twelve HIV-infected individuals a median percentage of apoptotic lymphocytes to be significantly higher than in ten healthy controls. To the best of our knowledge this is the first report of ex vivo observed increased apoptosis of peripheral blood lymphocytes in HIV-infected persons.