Three-color Staining Research Articles

Comparison of Bone Marrow Biopsy, Flow Cytometry and PCR Assays To Detect Bone Marrow Involvement in B-Cell Non-Hodgkin Lymphomas.

Bone marrow biopsy, (BMB) is essential to detect bone marrow (BM) infiltration in B-cell non-Hodgkin lymphomas (NHLs). Flow cytometry (FC) and PCR for clonal IgH rearrangement are considered as ancillary methods, but there is increasing evidence for their clinical usefulness. Observations dealing with combined use of the three methods still are lacking. Thus we carried out a retrospective study about the usefulness of an integrated approach to detect BM infiltration in NHLs. 193 patients suffering from NHLs (79 at presentation, 114 after chemotherapy alone or with: Rituximab, Campath-1, autologous BM transplantation), who had undergone simultaneous execution of BMB, and FC, and PCR from the myeloaspirate on the same iliac crest, were evaluated. BMB was carried out according to standard methods (infiltration pattern and immunohistochemistry). FC was performed using three-color staining, including CD45, to identify: κ/λ ratio, specific phenotype for CLL, MCL and HCL. PCR included identification of IgH rearrangement (CDR3 and VH families), BCL-1/JH translocation for MCL and BCL-2/JH translocation for follicular lymphoma.BMB, FC and PCR agreed in 142 cases and showed infiltration in 74 and lack of infiltration in 68. Cases at presentation were characterized by higher percentages of concordance than cases during the post-chemotherapy (84,8% vs 65.6%). Discrepant results were obtained in 51 cases (26.4%), 13 at presentation and 38 after treatment. In 17 specimens (8.8% of all cases, 33.3% of discordant cases), BM infiltration was detected only by PCR. In 12 of these samples (3 untreated and 14 treated) small B-cell percentages (0.50 ± 0.72, mean ± SD; range 0.02–3.00%) were present at FC. The remaining 5 cases (2.6%) were characterized by a lack of surface Ig expression and absence of specific phenotype: BMB was negative but IgH was clonal. 2 other cases with lack of surface Ig expression (for 7 cases in total, 3.6%), BMB-/PCR- were identified.Conversely, in 10 samples (5.2% of all cases, 19.6% of discordant specimens) PCR failed to detect BM infiltration, which was demonstrated by both FC and BMB. These specimens were characterized by high B-cell percentages (7 ± 8.25, mean ± SD; range 0.3–26.0%) and were obtained from 5 untreated and 5 treated patients.The remaining discordant cases were: 7 treated cases with BMB+/PCR+ and FC-; 6 cases (3 treated and 3 untreated) with FC+ and BMB-/PCR-; 3 treated cases with BMB- and FC+/PCR+; 3 cases (1 untreated and 2 treated) with BMB+ and FC-/PCR-. In the 3 treated cases with lack of amplification by PCR, the following results were observed: FC+/BMB+ in 1 case; FC-/BMB- in the remaining 2.Our data show that no single method is able to identify all cases of BM involvement in NHLs. BMB is actually considered the gold standard, however the combination of the three assays can increase the yields of detection of minimal residual disease. In fact, considering the three assays together as gold standard, BMB alone has a sensibility of 82.1%, a specificity of 96,3%, with 1.6% of false positive but 10.4% of false negative. The PCR can increase the sensibility and FC can than be considered as a valid confirmation assay, able to solve the cases when BMB and PCR show discrepancy.To conclude, the three assays are necessary to evaluate BM infiltration in NHLs, because BMB alone underestimate the BM involvement, especially following treatment.

Modulation of mThy28 nuclear protein expression during thymocyte development

We have recently shown that down-regulation of mouse Thy28 (mThy28) protein expression appears to be accompanied by apoptotic processes. Thymocytes from mice contain moderate amounts of mThy28 protein and undergo proliferation, differentiation, or apoptosis during murine thymic maturation. As a first step to examine the potential role of the mThy28 protein in the thymocyte development, such as positive–negative selection, the expression of mThy28 protein in the thymocyte subsets was examined. Thymocytes are separated into four subpopulations by the expression levels of CD4 and CD8: CD4 −CD8 − (DN), CD4 +CD8 + (DP), and CD4 +CD8 − or CD4 −CD8 + (SP). Flow cytometry analysis using three-color staining demonstrated that the mThy28 expression in immature DP cells is lower than that in DN and SP cells. The down-regulation of the mThy28 expression in the DP stage was also detected by Western blotting and reverse transcription–polymerase chain reaction (RT–PCR). The immunostaining method also showed that mThy28 protein was expressed in the medulla containing mature thymocytes, but not the cortex having immature thymocytes. The mThy28 protein in the thymocytes was mainly localized in the nucleus, as recently demonstrated in lymphoma cells, indicating that the mThy28 protein resides in the nucleus, irrespective of the cyclic or resting stage of the cell cycle. Together, the observation that mThy28 expression is down-modulated during the DP stage suggests that mThy28 protein might play some role in the positive–negative selection step in thymic maturation.

Long-lasting decrease of CD4+/CD45RA+ T cells in HCL patients after 2-chlorodeoxyadenosine (2-CdA) treatment.

The CD45RA and CD45RO isoforms of the leukocyte common antigen identify functionally distinct CD4+ T cell subsets: CD4+/CD45RA+ cells which represent a more 'naive' stage of T cell compartment and CD4+/CD45RO+ 'memory' cells. Phenotypic and functional abnormalities in T cell compartment have been frequently reported in patients with hairy cell leukemia (HCL) and, in more recent studies, a significant reduction in the absolute number of CD4+ lymphocytes bearing the CD45RO antigen has also been recorded. In our study we evaluated the CD45RA and CD45RO expression on CD4+ T cells by three-color staining in flow cytometry in 38 HCL patients, 19 untreated and 19 previously treated with 2-chlorodeoxyadenosine (2-CdA), administered at a daily dose of 0.1 mg/kg c.i. for 7 days. In HCL untreated patients, the proportion and the absolute number of CD4+/CD45RA+ and of CD4+/CD45RO+ T cell subsets were similar to normal controls. In contrast, HCL patients at 3-5 years by the end of treatment with 2-CdA, together with a reduction in the absolute number of CD4+ T cells, showed a persistent and significant decrease in the proportion and absolute number of CD4+/CD45RA+ cells as compared with both untreated HCL patients and normal controls (41 +/- 16% vs 57 +/- 14% and vs 65 +/- 7%) (P = 0.01 and 0.0001) and (0.201 +/- 0.137 x 10(9)/l vs 0.549 +/- 0.238 x 10(9)/l and vs 0.696 +/- 0.078 x 10(9)/l) (P = 0.00009 and P = 0.00001). In addition, together with the reduction of CD4+/CD45RA+ cells, we recorded a concomitant increase in the proportion of the CD4+/CD45RO+ cells as compared to untreated HCL patients and normal controls (62 +/- 16% vs 47 +/- 15% and vs 42 +/- 12%) (P = 0.08 and 0.02). These findings may suggest that CD4+/CD45RA+ cells are more sensitive than CD4+/CD45RO+ to the toxic effect of 2-CdA.

T cell alloreactivity induced by normal G-CSF-mobilized CD34+ blood cells.

In this study, the hypothesis that a subset of granulocyte colony-stimulating factor (G-CSF)-mobilized CD34+ blood cells may actively induce an allogeneic T cell response in vitro was tested. Circulating CD34+ cells were purified to > or =98% by high gradient magnetic separation and then analyzed for the coexpression of HLA-DR, the common beta-chain of the leukointegrin family CD18 and costimulatory molecules CD80 (B7-1) and CD86 (B7-2). These antigens were expressed on average on: 94.9 +/- 2.5%, 64.4 +/- 15.4%, 0% and 1.9 +/- 1.2% CD34+ blood cells, respectively. Irradiated CD34+ cells induced a high proliferative response of allogeneic, but not autologous, purified CD4+ and CD8+ T cells in primary mixed leukocyte culture (MLC). An average three-fold lower CD4+ and CD8+ T cell response was induced by mononuclear cells from G-CSF-treated donors. A lower frequency of allostimulating cells among mononuclear cells rather than among CD34+ cells in the apheresis was documented by limiting dilution assay (LDA). As previously observed with marrow, sorted CD34+/CD18+ cells induced the proliferation of allogeneic T cells in MLC, while CD34+/CD18- cells, which were >94% HLA-DR+ and contained both committed (CFU-C) and early (LTC-IC) hematopoietic progenitors, stimulated allogeneic T cells poorly. Three-color staining cytofluorimetry indicated that expression of CD80 and CD86 were upregulated in 6.9 +/- 4.9 and 10.7 +/- 2.6% CD34+ blood cells respectively, after 24-30 h of culture with autologous or allogeneic mononuclear cells, or with CD4+, or CD8+ T cells, but not with medium alone. Moreover, the upregulation of CD86 was observed on CD34+/CD18+ rather than on CD34+/CD18- cells after 30 h in MLC. Blocking experiments demonstrated that preincubation of stimulator and responder cells with anti-CD80 plus anti-CD86 monoclonal antibodies induced a 84 +/- 8% inhibition of CD34+ cell allostimulating activity after 6 days in primary MLC. These results suggest that G-CSF-mobilized CD34+ hematopoietic progenitors with alloantigen presenting function express CD18 and may upregulate CD80 and CD86 upon interaction with T cells. Since activation of B7 costimulatory molecules represents an active costimulatory pathway on G-CSF-mobilized CD34+ cells, the blockade of these molecules or, alternatively, the use of selected non-immunogenic CD34+/CD18- blood stem cells may represent a new strategy for reducing graft rejection and overcoming HLA barriers in allogeneic stem cell transplantation.

Fluorescence Counter-Staining of Cell Nuclear DNA for Multi-Color Laser Confocal Microscopy.

Twenty-one nucleic acid-specific fluorochromes were examined for use in cell nuclear counter-staining of specimens observed under a laser confocal microscope equipped with a Krypton/argon laser tube. Six green, three red, and two far-red fluorochromes gave sufficient fluorescence. Among them, SYBR Green I, Pico Green, SYTOX Green, YO-PRO-3, and TO-PRO-3 specifically stained the cell nuclear DNA. Other fluorochromes except POPO-3 stained the cell nuclear DNA and co-stained the cytoplasmic RNA. Conversely, POPO-3 specifically stained the cytoplasmic and nucleolar RNA. Anti-bleaching reagents (PPDA and DABCO) effectively prevented the photobleaching of SYBR Green I, Pico Green, YO-PRO-3, and TO-PRO-3, whereas DABCO accelerated the photobleaching of SYTOX Green. Taking into account the characteristics of these fluorochromes, SYBR Green I, YO-PRO-3, and TO-PRO-3 were best suited for cell nuclear counter-staining as green, red, and far-red fluorochromes, respectively. Especially, TO-PRO-3 seems to be the most useful because its far-red fluorescence enables three-color fluorescence staining by combination with immunofluorescence labeling with fluorescein and rhodamine derivatives.

Toward a new reference method for the leukocyte five-part differential

A flow cytometric method performing a five-part leukocyte differential based on three-color staining with anti-CD45-fluorescein isothiocyanate (FITC), anti-CD-14-phycoerythrin (PE)/Cy5, and a cocktail of PE-labeled anti-CD2, anti-CD16, and anti-HLA-DR antibodies was evaluated. Results obtained by using three different sample preparation procedures and two different flow cytometers were compared with those of a 1,000-cell manual differential for evaluation of accuracy. We observed excellent correlations with the manual differential for all leukocyte subclasses and even higher correlations between the different flow cytometric methods. Flow cytometric basophil results were identical to the manual counts, regardless of which sample preparation technique or flow cytometer was used. Therefore, we propose our flow cytometric method as the first acceptable automated reference method for basophil counting. The flow cytometric results for the other leukocyte subclasses were apparently influenced by the sample preparation, which could not be explained by cell loss during washing steps. Moreover, a small influence of the flow cytometer was also observed. Assessing the influence of sample storage, we found only minimal changes within 24 h. In establishing reference values, high precision of flow cytometric results facilitated detection of a significantly higher monocyte count for males (relative count: 7.08 +/- 1.73% vs. 6.44 +/- 1.33%, P < 0.05; absolute count: 0.536 +/- 0.181 x 10(9)/liter vs. 0.456 +/- 139 x 10(9)/liter, P < 0.01). Our data indicate that monoclonal antibody-based flow cytometry is a highly suitable reference method for the five-part differential: It also shows, however, that studies will have to put more emphasis on methodological issues to define a method that shows a high interlaboratory reproducibility.

Chloromethyl-X-Rosamine is an aldehyde-fixable potential-sensitive fluorochrome for the detection of early apoptosis.

Early apoptosis is invariably accompanied by a disruption of inner mitochondrial transmembrane potential (delta psi m). Cationic lipophilic fluorochromes, such as 3,3' dihexyloxacarbocyanine iodide (DiOC6(3)), rhodamine 123, or 5,5', 6,6'-tetrachloro-1,1', 3,3'-tetraethylbenzimidazolcarbocyanine iodide (JC-1), can be used to measure such an apoptotic delta psi m dissipation. However, these dyes are afflicted by the handicap that cytofluorometric analyses must be performed ad hoc on nonfixed, metabolically active cells. Here, we show that chloromethyl-X-rosamine (CMXRos) is a viable alternative to other delta psi m-sensitive probes, and that it allows for formaldehyde fixation of cells before analysis. Using this fluorochrome, we developed a three-color staining technique in which two fluorochromes (fluorescein isothiocyanate and phycoerythrin) coupled to antibodies are employed to determine expression of cell-surface antigens, and CMXRos is used to measure delta psi m. In addition, we developed an approach to assess simultaneously delta psi m and expression of intracellular antigens. Thus, the expression of Bc1-2, a mitochondrial outer-membrane protein, can be determined after staining with CMXRos, fixation, and cell permeabilization. CMXRos labeling can also be combined with determination of apoptotic DNA fragmentation using the Tunel technique. In conclusion, CMXRos provides several methodological advantages over other, nonfixable fluorochromes used for delta psi m determination.

κ+λ+ dual receptor B cells are present in the human peripheral repertoire.

It is a common notion that mature B lymphocytes express either kappa or lambda light (L) chains, although the mechanism that leads to such isotypic exclusion is still debated. We have investigated the extent of L chain isotypic exclusion in normal human peripheral blood B lymphocytes. By three-color staining with anti-CD19, anti-kappa, and anti-lambda antibodies we could estimate that 0.2-0.5% of peripheral blood B cells from healthy adults express both kappa and lambda on the cell surface. The kappa+lambda+ cells were sorted, immortalized by Epstein-Barr virus, and five independent clones were characterized in detail. All clones express both kappa and lambda on the cell surface and produce immunoglobulin M that contain both kappa and lambda chains in the same molecule, i.e., hybrid antibodies. Sequencing of the L chains revealed in three out of five clones evidence for somatic mutations. It is interesting to note that among a panel of single receptor B cell clones we identified two lambda+ clones that carried a productively rearranged kappa, which was inactivated by a stop codon generated by somatic mutation. These findings indicate that dual receptor B lymphocytes can be found among mature antigen-selected B cells and suggest that somatic mutation can contribute to increase the degree of isotypic exclusion by inactivating a passenger, nonselected L chain.

γδ T-Cell Fraction of Peripheral Blood Is Increased in Recurrent Aphthous Ulceration

Recurrent aphthous ulceration (RAU) is the most common oral mucosal disease. The etiology is unresolved but several studies have suggested a systemic immunoregulatory imbalance in the patients. The purpose of the present study was to assess possible signs of immunologic deficiency or activation of peripheral blood mononuclear cells in patients with RAU by flow cytometry using three-color immunofluorescent staining which has not previously been employed in this patient category. The population consisted of 13 and 14 otherwise healthy patients with active and inactive RAU, respectively, and 18 healthy volunteers with a negative RAU history served as controls. The most striking observation was an increased fraction of T-cell receptor (TCR)-γδ + cells in patients with active RAU (median percentage 8.5) compared with controls (median percentage 2.8; P < 0.001) and patients with inactive RAU (median percentage 5.0; P < 0.01). The fraction of peripheral TCR-γδ cells has not previously been determined in patients with RAU but the increased figures during active disease might reflect an immunologic stimulation during exacerbation. The nature of the stimulus remains to be established, but recent studies suggest that varicella zoster virus and/or cytomegalovirus may be involved. The pntential role of TCR-γδ cells in RAU lesions has not yet been investigated but appears to be an obvious issue for future studies.

Phenotype analysis of cycling and postcycling thymocytes: Evaluation of detection methods for BrdUrd and surface proteins

We present a comparison of two different methods for simultaneous detection of bromodeoxyuridine and cell surface markers. Both methods use enzymatic generation of single-strand DNA with nuclease. The biological system used is the murine thymus, in which in vivo DNA synthetizing cells were labeled by injection of BrdUrd and analyzed at different time points after the nucleoside pulse. The surface proteins detected were CD4 and CD8 differentiation markers and the T-cell receptor. Extraction of DNA-associated proteins with 0.1N HCl and detergent is necessary for the action of EcoR1 and Exonuclease III, but this treatment destroys phycocyanins and induces cell aggregation, as shown using the doublet-discrimination module. For DNAse I action, cells could be treated with paraformaldehyde and a low concentration of Tween 20, and this treatment was adequate for surface staining preservation (even with phycocyanins) and BrdUrd detection. Both methods were adequate for cell cycle studies, but only 7-amino-actinomycin D could be used as total DNA dye after DNAse action, and good results needed long (48-72 h) incubation in the fixative-detergent mixture. The DNAse I method now allows three-color staining (two surface markers and Brd-Urd), analyzed in a one laser-cytometer for the study of the phenotype of cycling cells, and of their progeny, in vivo and in cell cultures. It also allows the quantitative analysis of cell surface receptor densities in conditions similar to fresh cells.

Activated T lymphocytes in the celiac lesion: non-proliferative activation (CD25) of CD4+ alpha/beta cells in the lamina propria but proliferation (Ki-67) of alpha/beta and gamma/delta cells in the epithelium.

In order to identify any dominating subset of activated T cells in the celiac lesion, we examined CD3+, CD4+, CD8+ and T cell receptor (TcR) gamma/delta+ lymphocytes in jejunal cryosections from 25 patients with celiac disease and 10 controls by three-color immunofluorescence staining for expression of the nuclear proliferation marker detected by monoclonal antibody (mAb) Ki-67 and the p55 alpha chain of interleukin-2 receptor (CD25). mAb Ki-67+ intraepithelial lymphocytes (IEL) were exclusively observed in celiac patients. The median proportion of CD3+ IEL positive for Ki-67 increased from nil in controls to 4.5% in partly treated (range 0-19.0%; n = 10; p = < 0.05) and 12.8% in untreated celiac disease (range 4.0-30.7%; n = 15; p < 0.005). Only 1.5% of CD3+ subepithelial T cells expressed the Ki-67 marker in celiac disease (range 0-9.5%). Two- and three-color staining combining mAb to CD3 and Ki-67 with mAb to CD4, CD8 or TcR delta showed that both TcR alpha/beta+ CD8+ and TcR gamma/delta+ (but not CD4+) mucosal T cells proliferated in the epithelium. By contrast, CD25 were almost exclusively expressed on CD4+ T cells in the lamina propria. The percentage of CD25+ T cells increased significantly from 1.7% in controls (range 0-2.9%) to 7.5% in partly treated (range 0.8-17.8%, p < 0.002), and to 14.65% in untreated celiac disease (range 3.9-21%, p < 0.002). These results suggest that gluten ingestion in celiac disease induces proliferative activation of TcR alpha/beta+ CD8+ and TcR gamma/delta+ IEL but non-proliferative activation (lymphokine production?) of lamina propria CD4+ T cells.

Rapid immunophenotypic characterization of chromosomally aberrant cells by the new FICTION method.

Recently, we have presented a new technique for immunophenotyping cells that have numerical chromosome aberrations. We referred to this method as "Fluorescence-Immunophenotyping and Interphase Cytogenetics as a Tool for Investigation of Neoplasms" (FICTION). We present here an advanced FICTION method with three-color staining and improved sensitivity.

Nature of the thymocytes associated with dendritic cells and macrophages in thymic rosettes

Thymic rosettes, structures consisting of 3–30 thymic lymphoid cells attached to a central macrophage or dendritic cell, were released from mouse thymus tissue by collagenase digestion. They were shown to be preexistent structures within the thymus, but to be subject to extensive exchange with free thymocytes under certain conditions. An isolation procedure was developed, using a new technique of zonal unit-gravity elutriation, which minimized exchange and produced a completely pure sample of the larger rosettes. The rosette-associated thymocytes were analyzed by two- and three-color immunofluorescent staining and flow cytometry. The dominant cell type was a small, CD4 +CD8 +, cortical-type thymocyte. However, all of the established thymus subpopulations defined by CD4 and CD8, including CD4 −CD8 + and CD4 +CD8 − mature thymocytes and CD4 −CD8 − early thymocytes, were also present in rosettes. Very few of the cells present were of an intermediate or transitional phenotype. Rosette-associated thymocytes were somewhat enriched in large dividing thymocytes, in CD4 −CD8 − thymocytes, and in mature thymocytes expressing the T-cell antigen receptor-CD3 complex. Their most striking characteristic was a marked depletion in small thymocytes lacking surface H-2K expression, a major population among free thymocytes. The physiological role of the rosette structure is discussed, and it is suggested that the heterogeneity of the associated thymocytes in part reflects the existence of different types of rosettes in different areas of the thymus.