Fluorescence depolarization as an early measure of T lymphocyte stimulation

Clinical application of static fluorescence-based cytometry, Cellscan, in cutaneous adverse drug reaction

The aim of the present study was to evaluate the effectiveness of Cellscan in identifying culprit drugs causing cutaneous adverse drug reaction. It was a prospective study with 3 months follow up conducted at the Departments of Dermatology, Internal Medicine and Dermatology Outpatient Clinic, Chaim Sheba Medical Center, Tel Hashomer, Israel. The study included 36 patients with cutaneous reaction suspected to be secondary to drugs, treated with a total number of 148 drugs. All patients and drugs were classified to three probability groups according to accepted clinical criteria. The effectiveness of the Cellscan test in identifying the culprit drug was addressed according to the clinical probability for cutaneous drug reaction, the drug class and the type of rash. Data analysis according to the clinical probability for cutaneous drug reaction revealed that patients in the moderate and high probability groups had a high test sensitivity of 77.7% and 83.3% with specificity of 71% and 63%, respectively, in identifying the culprit drug. Classifying the data according to drug classes, revealed that for the antibiotic and cardiovascular drug classes the sensitivity of the test was 100% and 92% with specificity of 83.3% and 55.5%, respectively, in identifying the culprit drug. Finally, the classification of patients according to the type of rash revealed a high evaluating accuracy for culprit drugs in maculopapular rashes with sensitivity and specificity of 90% and 60.4%, respectively. The results of this study imply that the Cellscan test is it a good practical tool for identifying the culprit drug in cutaneous adverse drug reaction.

The Immunosuppressive Effect of Methotrexate in Active Rheumatoid Arthritis Patients vs. its Stimulatory Effect in Nonactive Patients, as Indicated by Cytometric Measurements of CD4 + T Cell Subpopulations

This cytometric study assesses the effects of methotrexate (MTX) on the expanded CD4+ lymphocyte population in active and nonactive rheumatoid arthritis (RA) patients. In the active patients, MTX was found to reduce the predominant CD4+ CD28+ subpopulation (by 30%), and the minor subpopulation of CD4+ CD28- (by 34%). The incidence of CD25 phenotype was downregulated by 15%. These reductions can be attributed to immunosuppression through apoptosis, which was demonstrated by MTX-induced fluorescein diacetate (FDA) hyperpolarization (an established indicator of early apoptosis). In contrast, in nonactive RA patients, the major CD4+ CD28+ subpopulation of small lymphocytes appeared to be activated by MTX, subsequently transforming into a major hyperblast population, whereas the minor CD4+ CD28- subpopulation was not affected by MTX treatment. The activation by MTX in this group of patients is evidenced by MTX-induced FDA depolarization (an indicator of early activation). Thus, MTX immunosuppressive effect on CD4+ subsets was found in active patients, whereas immunostimulation by MTX was shown in nonactive patients. The found discriminative effect of MTX may suggest a higher effectiveness of low-dose MTX therapy in active RA patients.

Comparative analysis of cell parameter groups for breast cancer detection

We present a method for the comparative analysis of parameter groups according to their correlation to disease. The theoretical basis of the proposed method is Information Theory and Nonparametric Statistics. Normalized mutual information is used as the measure of correlation between parameters, and statistical conclusions are based on ranking. The fluorescence polarization (FP) parameter is considered as the principal diagnostic characteristic. The FP was measured in fluorescein diacetate (FDA)-stained individual peripheral blood mononuclear cells (PBMC), derived from healthy subjects and breast cancer (BC) patients, under different stimulation conditions: by tumor tissue, the mitogen phytohemagglutinin (PHA) or without the stimulants. The FP parameters were grouped according to their correlation with breast cancer. It was established that the greatest difference between cells of BC patients and healthy subjects is found in the PHA test (parameter P1).

Application of a static fluorescence-based cytometer: the CellScan in clinical immunology

The CellScan system is a laser scanning cytometer which enables repetitive fluorescence intensity (FI) and polarization (FP) measurements in living cells, as a means of monitoring lymphocyte activation. By monitoring FP changes in peripheral blood lymphocytes (PBL) following exposure to antigenic stimuli, the CellScan may have a role in the diagnosis of autoimmune diseases. Monitoring changes in FI and FP in PBLs from patients with atherosclerosis following exposure to various stimuli, has illustrated the role of the immune system in the atherosclerotic process. The CellScan has also been evaluated as a diagnostic tool for drug-induced allergy, based on FP reduction in PBLs following incubation with the suspected drugs. FI and FP changes in cancer cells have been found to correlate with the cytotoxic effect of different anti-neoplastic drugs, illustrating the potential role of the CellScan system in clinical oncology. In conclusion, the CellScan is a promising new tool with a variety of applications in cell biology, immunology, cancer research and clinical pharmacology.

Application of a static fluorescence-based cytometer (the CellScan) in basic cytometric studies, clinical pharmacology, oncology and clinical immunology

The CellScan apparatus is a laser scanning cytometer enabling repetitive fluorescence intensity (FI) and polarization (FP) measurements in living cells, as a means of monitoring lymphocyte activation. The CellScan may serve as a tool for diagnosis of rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) as well as other autoimmune diseases by monitoring FP changes in peripheral blood lymphocytes (PBLs) following exposure to autoantigenic stimuli. Changes in FI and FP in atherosclerotic patients' PBLs following exposure to various stimuli have established the role of the immune system in atherosclerotic disease. The CellScan has been evaluated as a diagnostic tool for drug-allergy, based on FP reduction in PBLs following incubation with allergenic drugs. FI and FP changes in cancer cells have been found to be well correlated with the cytotoxic effect of anti-neoplastic drugs. In conclusion, the CellScan has a variety of applications in cell biology, immunology, cancer research and clinical pharmacology.

Monitoring of Intracellular Enzyme Kinetic Characteristics of Peripheral Mononuclear Cells in Breast Cancer Patients

A new methodology for the detection of functional response of peripheral blood mononuclear cells against breast cancer (BC) antigens was developed. The method is based on cellular enzymatic activity measurements, using a fluorogenic substrate. We used this method to estimate the kinetic activity of lymphocytes derived from cancer patients and healthy donors. The aim of the study was to determine a possible correlation between the basic characteristics (K(m) and V(max)) of biochemical enzymatic reactions in live peripheral white mononuclear cells and common clinical-pathological characteristics in BC patients. Our method shows that the enzymatic activity, upon interaction with mitogen or tumor antigens, of the peripheral blood cells in BC patients is different from the enzymatic reactions in healthy individuals. This holds true in the early stages, and the difference persists throughout all of the stages of the disease. This difference is manifested, primarily, by an increase in the K(m) values after cell incubation with tumor tissue. It was also demonstrated that higher K(m) values of tumor tissue-activated peripheral blood mononuclear cells are associated with a better prognostic status of the BC patients (lymph node-negative tumors, hormone receptor preservation, and the absence of Her-2/neu protein overexpression). Thus, the present methodology may serve as an additional criterion for prognosis and monitoring, both in BC patients, and in individuals associated with high cancer risk.

Ratiometric fluorescence polarization as a cytometric functional parameter: theory and practice

The use of ratiometric fluorescence polarization (RFP) as a functional parameter in monitoring cellular activation is suggested, based on the physical phenomenon of fluorescence polarization dependency on emission wavelengths in multiple (at least binary) solutions. The theoretical basis of this dependency is thoroughly discussed and examined via simulation. For simulation, aimed to imitate a fluorophore-stained cell, real values of the fluorescence spectrum and polarization of different single fluorophore solutions were used. The simulation as well as the experimentally obtained values of RFP indicated the high sensitivity of this measure. Finally, the RFP parameter was utilized as a cytometric measure in three exemplary cellular bioassays. In the first, the apoptotic effect of oxLDL in a human Jurkat FDA-stained T cell line was monitored by RFP. In the second, the interaction between cell surface membrane receptors of human T lymphocyte cells was monitored by RFP measurements as a complementary means to the fluorescence resonance energy transfer (FRET) technique. In the third bioassay, cellular thiol level of FDA- and CMFDA-labelled Jurkat T cells was monitored via RFP.

Simultaneous monitoring of binding to and activation of tumor-specific T lymphocytes by peptide-MHC

The recent advent of peptide-MHC tetramers has provided a new and effective tool for studying antigen-specific T cell populations through monitoring tetramer binding to T cells by flow cytometry. Yet information regarding T cell activation induced by the bound tetramers cannot be deduced from binding studies alone; complementary methods are needed to bridge this gap. To this end, we have developed a new approach that now enables monitoring both binding to and activation of T cells by peptide-MHC tetramers at the single-cell level. For this purpose, we have employed the CellScan, a non-flow cytometer designed for repetitive measurements of optical parameters (e.g., fluorescence intensity and polarization) of individual living cells. A melanoma-specific MART1 CTL line and a gp100-specific CTL clone were incubated with specific and control single-chain peptide-MHC tetramers for 45 min. Subsequently, the fluorescence intensity and polarization were measured by the CellScan. Specific binding of fluorescently labeled peptide-MHC tetramers to CTLs, recorded by the CellScan, was comparable to that measured by flow cytometry. CellScan monitoring of the degree of fluorescence polarization of fluorescein diacetate-labeled CTLs that were reacted with tetramers revealed specific activation of the CTLs, which was confirmed by cytokine (INF gamma) production. These results provide a new means of monitoring both the binding to and activation of T lymphocytes by cognate peptide-MHC complexes at the single-cell level, which can now be applied to distinguish between cognate responding and anergic T cells.

The induction of apoptosis by methotrexate in activated lymphocytes as indicated by fluorescence hyperpolarization: a possible model for predicting methotrexate therapy for rheumatoid arthritis patients

The objectives of this study were to test the in vitro response of healthy non-activated, activated, and rheumatoid arthritis (RA) lymphocytes to methotrexate (MTX), and design an in vitro model for predicting the efficiency of MTX treatment for RA patients. Considering the RA profile of clonal-expanded CD4(+) T cells, phytohemagglutinin-activated mononuclear cells taken from healthy donors were incubated with different concentrations of MTX. The MTX-immunosuppressive effect was tested by fluorescence intensity measurements, including PI assay and annexin V assay. For simple detection, we used the Individual Cell Scanner (IC-S), which enables the measurement of early events in individual cells. Healthy mononuclear cells (MNC), and MNC derived from RA patients, were tested by the IC-S while utilizing fluorescence polarization (FP) measurements of fluorescein diacetate (FDA) as an established marker of activation or suppression. In healthy activated MNC, we found that MTX, through its early incubation period, interferes with the activation signal obtained by PHA and exerts an apoptotic signal, which is noted by increases in the FP. Comparing our model to six long-standing RA patients and five newly-diagnosed patients revealed significant differences in the FP measurements, including fluorescence depolarization as an early established measurement of lymphocyte activation, and hyperpolarization as a measurement of an early immunosuppressive effect. We conclude that MTX, an effective therapy for RA patients, could easily be tested by fluorescence polarization measurements of FDA before (or during) clinical use in order to predict its efficiency on a specific RA patient. Moreover, the FP measurements can be used for the diagnosis, and making timing and dosage decisions.

Fluorescein fluorescence hyperpolarization as an early kinetic measure of the apoptotic process

The ability to identify apoptotic cells within a complex population is crucial in the research and diagnosis of normal physiology and disease states. The Cellscan mark S (CS-S) cytometer was used in this study to detect intracellular fluorescence intensity and polarization (FI and FP) in several well-established models of apoptosis: Following spontaneous apoptosis, as well as glucocorticoid or anti Fas-induced apoptosis, CS-S individual cell-based analysis revealed the appearance of a cell cluster characterized by low FI and high FP. Temporal analysis of annexine V binding and FP measurements following DXM treatment showed that hyperpolarization preceded phosphatidylserine appearance on the outer plasma membrane. The early increase in FP was found to be dose dependent and inversely related to cell diameter. Cell dehydration and alteration of plasma membrane transport properties, both occurring during early stages of apoptosis, may be involved in the phenomena of intracellular fluorescein hyper-polarization in apoptosis.

Analysis of enzyme kinetics in individual living cells utilizing fluorescence intensity and polarization measurements

BACKGROUND

The Cellscan mark-S (CS-S) scanning cytometer was used for tracing enzymatic reactions in the same individual cells under various physiological conditions over periods of minutes. On-line reagent addition and changes in the experimental conditions (buffers, ions, substrates and inhibitors) were performed.

METHODS

Kinetic events were monitored by fluorescence intensity (FI) and fluorescence polarization (FP) measurements of fluorescein diacetate (FDA) and chloromethyl fluorescein diacetate (CMFDA) intracellular hydrolysis. FP measurements have been used to assess the intracellular marker's mobility restrictions.

RESULTS

Kinetic measurement along 1000 s of FDA labeled individual Jurkat T cells, indicated variation of 65% for FI(t) and approximately 10% for FP(t). While FI increased linearly with time, FP(t) decreased nonlinearly and asymptotically, reaching a constant value. The FP(t) of CMFDA-labeled cells was different from that of FDA-labeled cells. Average cellular Km of 3.9 microM was calculated from individual cell FDA hydrolysis curves.

CONCLUSIONS

(1) Analysis of the reaction kinetics of intracellular enzymes can be refined by using FP measurements of the products of fluorogenic substrates in addition to the FI measurements. (2) Subpopulations or individual cells could be classified according to their reaction rates. (3) A specific dependence of FP(t) on type of enzyme substrate is suggested.

Determination of cellular thiol levels in individual viable lymphocytes by means of fluorescence intensity and polarization

Cellular thiol levels regulate lymphocyte proliferation and death and play a significant role in the immune response. Therefore, the ability to analyze the total protein and non-protein thiol compounds and their distribution among individual living lymphocytes is of great importance. A quantitative measurement of intracellular sulphydryl groups in living lymphocytes using the Cellscan mark F (CS-F) cytometer, in conjunction with the probe CMFDA, is described. This technique permits the detection, identification, and study of sub-populations and single cells in a sample of heterogeneous lymphocytes. The Cellscan apparatus is a laser based scanning cytometer incorporating a unique cell carrier which allows repeated, high-precision measurements of fluorescence intensity (FI) and fluorescence polarization (FP) to be made on intact individual living cells under controlled physiological conditions. The discernible effect of fluorophore molecules bound to thiols having a higher FP than free molecules was used to estimate their relative fractions in living lymphocytes. The results were more conspicuous when the ratio between FP measured at two wavelengths (FPR) of the fluorogenic molecules was used for analysis. In addition, the intracellular dynamic changes in the FI, FP and FPR of the fluorescent probe were also monitored. The cellular sulphydryl content of each lymphocyte within a population was recorded by the CS-F, and sub-populations or individual cells were classified according to their thiol levels and their metabolic rates. Changes in thiol concentration were observed following mitogenic activation of peripheral lymphocytes.

The trace and subgrouping of lymphocyte activation by dynamic fluorescence intensity and polarization measurements

Cell activation involves conformational changes of cytosolic enzymes, and/or their regulatory proteins, as well as intracellular matrix re-organization. In this work, these changes were monitored by dynamic measurements of fluorescence polarization in single cells incubated with or without phytohaemagglutinin (PHA), using the Cellscan mark S (CS-S) cytometer. This instrument and the procedure used proved to be a powerful tool for distinguishing subpopulations of cells. Grouping of cells by their staining rates (the time rate of change of the fluorescence intensity) yielded three major subgroups. For each subgroup, the fluorescence depolarization (FDP) induced by the incubation with PHA was measured. The kinetics of the subgroups indicate that the major FDP is contributed by the cells with the lowest staining rate. This FDP is approximately 1.5 times greater than that of a bulk population. It is believed that the analysis of kinetic probing might yield an important and more sensitive method for functional marking of subgroups of cells by their response characteristics.

Reactivity of peripheral blood lymphocytes to oxidized low-density lipoprotein: a novel system to estimate atherosclerosis employing the Cellscan

BACKGROUND

The assumption that atherosclerosis involves an autoimmune response to oxidized LDL (oxLDL) is based on the presence of immunocompetent cells and immunoglobulin deposition in the atherosclerotic lesions by successful immunomodulation of the atherosclerotic process and by inhibition of experimental atherosclerosis by antioxidants. The Cellscan system is a multiparameter laser-based static cytometer that enables repeated monitoring of the fluorescence intensity (FI) and polarization (FP) of individual living cells. Analysis of intracellular fluorescein fluorescence polarization (IFFP) has previously been used to define activated lymphocyte population.

HYPOTHESIS

In this study, the Cellscan apparatus has been used to monitor cellular response to oxLDL in patients with atherosclerosis and in controls.

METHODS

The FI and FP of fluorescein diacetate (FDA)-labeled peripheral lymphocytes were measured following exposure to oxLDL in vitro. Using cluster analysis we were able to identify subpopulations of cells that were characterized by their FI and FP. Forty-two subjects were studied: 22 patients with severe coronary heart disease and 22 control individuals, either healthy or with other diseases.

RESULTS

Fluorescence intensity of fluorescein-labeled peripheral blood lymphocytes (PBL) was markedly decreased upon exposure to high doses (> 25 micrograms/ml) of oxLDL concurrently with an increase in FP. A specific and dose-dependent reduction in FP of the high-intensity cell subpopulations, accompanied by higher FI, was evident in patients with ischemic heart disease upon exposure to low doses of oxLDL (up to 25 micrograms/ml). Maximal depolarization was shown upon triggering with 2 micrograms/ml oxLDL. The polarization ratio (the mean polarization value of the specific cell population with and without activation) obtained for patients' lymphocytes was significantly lower (p < 0.01) than that of the control group (0.936 +/- 0.05 and 1.028 +/- 0.055, respectively).

CONCLUSION

These data suggest that PBL from patients with active ischemic heart disease show an increased reactivity to oxLDL. A 73% positivity rate was found for ischemic heart disease patients compared with 5% in the control subjects. One of the future prospects of this study might be the advent of a simple and rapid noninvasive test that could assess the extent of atherosclerosis, and possibly even the response to therapy, by monitoring the reactivity of PBL to oxLDL.

Preparation of a diagnostic antigen of human melanoma based on lymphocyte activation as measured by intracellular fluorescein fluorescence polarization

The intracellular fluorescein fluorescence polarization (IFFP) test indicates that peripheral blood lymphocytes (PBL) of cancer patients display stimulatory sensitivity to a short incubation with specific tumor protein extracts. In this work, a human lymphocyte activation melanoma antigen (LAMA) was purified from supernatant of a human melanoma cell line (L1M1), which could specifically stimulate lymphocytes of melanoma patients. The results showed a significant stimulation of lymphocytes from healthy donors after incubation with phytohaemagglutinin (PHA), while no stimulation was observed after incubation with LAMA. On the other hand, lymphocytes from melanoma patients showed a significant stimulation with LAMA, while generally showing minor or no stimulation with PHA. Melanoma specificity of LAMA was demonstrated by no response in lymphocytes from patients of lung, colon, or breast cancer. The purified fraction is therefore considered to be a shared tissue-specific antigen which may be useful in immunodiagnosis and immunotherapy of melanoma.