Determination of the antibody binding capacity of lymphocyte membrane antigens by flow cytometry in 58 blood donors

A Mechanistic Physiologically-Based Pharmacokinetic Platform Model to Guide Adult and Pediatric Intravenous and Subcutaneous Dosing for Bispecific T Cell Engagers

Bispecific T cell engagers (Bi-TCEs) have revolutionized the treatment of oncology indications across both liquid and solid tumors. Bi-TCEs are rapidly evolving from conventional intravenous (i.v.) to more convenient subcutaneous (s.c.) administrations and extending beyond adults to also benefit pediatric patients. Leveraging clinical development experience across three generations of Bi-TCE molecules across both liquid and solid tumor indications from i.v./s.c. dosing in adults and pediatric subjects, we developed a mechanistic-physiologically-based pharmacokinetic (PBPK) platform model for Bi-TCEs. The model utilizes a full PBPK model framework and was successfully validated for PK predictions following i.v. and s.c. dosing across both liquid and solid tumor space in adults for eight Bi-TCEs. After refinement to incorporate physiological ontogeny, the model was successfully validated to predict pediatric PKs in 1 month - < 2 years, 2-11 years, and 12-17 years old subjects following i.v. dosing. Following s.c. dosing in pediatric subjects, the model predicted similar bioavailability, however, a shorter time to maximum concentration (Tmax ) for the three age groups compared with adults. The model was also applied to guide the dosing strategy for first generation of Bi-TCEs for organ impairment, specifically renal impairment, and was able to accurately predict the impact of renal impairment on PK for these relatively small-size Bi-TCEs. This work highlights a novel mechanistic platform model for accurately predicting the PK in adult and pediatric patients across liquid and solid tumor indications from i.v./s.c. dosing and can be used to guide optimal dose and dosing regimen selection and accelerating the clinical development for Bi-TCEs.

Combination of dociparstat sodium (DSTAT), a CXCL12/CXCR4 inhibitor, with azacitidine for the treatment of hypomethylating agent refractory AML and MDS

Leukemia stem cells utilize cell adhesion molecules like CXCR4/CXCL12 to home to bone marrow stromal niches where they are maintained in a dormant, protected state. Dociparstat sodium (DSTAT, CX-01) is a low anticoagulant heparin with multiple mechanisms of action, including inhibition of the CXCR4/CXCL12 axis, blocking HMGB1, and binding platelet factor 4 (PF-4). We conducted a pilot study adding DSTAT to azacitidine for patients with AML or MDS unresponsive to or relapsed after prior hypomethylating agent therapy, hypothesizing that DSTAT may improve response rates. Twenty patients were enrolled, with a median of 2 prior lines of therapy and 6 cycles of prior hypomethylating agents. Among fifteen patients evaluable for response, there was 1 complete remission, and 3 marrow complete remissions, for a response rate of 27 % among evaluable patients (20 % overall). Hematologic improvement was observed in 5 additional patients. The median overall survival for all enrolled patients was 205 days (95 % CI 119-302). While cytopenias and infections were common, these were not out of proportion to what would be expected in this population of patients undergoing treatment with azacitidine alone. In summary, this trial demonstrated the feasibility of combining DSTAT with azacitidine, with several responses observed, suggesting this combination warrants further study.

Strategies for the measurements of expression levels and half-lives of HLA class I allotypes

HLA class I molecules are highly polymorphic cell surface proteins that trigger immune responses by CD8⁺ T cells and natural killer (NK) cells. Most humans express six different HLA class I proteins encoded by the HLA-A, HLA-B and HLA-C genes. HLA class I molecules bind to peptide antigens and present these antigens to T cell receptors (TCR) of CD8⁺ T cells. HLA class I expression levels also regulate NK cell activation. The presence of individual HLA class I genes is linked to many different disease, transplantation and therapy outcomes. An understanding of HLA class I expression and stability patterns is fundamentally important towards a better understanding of the associations of HLA class I genes with disease and treatment outcomes, and towards HLA class I targeting for vaccine development. Quantitative flow cytometry allows for assessments of variations in expression levels of HLA class I molecules in cells from a single blood donor over time, as well as averaged measurements across donors for the same allotype. Since all HLA class I molecules are structurally-related, cellular measurements of the HLA class I expression levels and stabilities of individual variants in human cells require careful choices of donors and antibodies, which are discussed here.

Standardization, Calibration, and Control in Flow Cytometry

Because flow cytometers are designed to measure particle characteristics, particles are the most common materials used to calibrate, control, and standardize the instruments. Definitions and cautions are provided for common terms to alert the reader to critical distinctions in meaning. This unit presents extensive background on particle types and cautions and describes practical aspects of methods to standardize and calibrate instruments. Procedures are provided to characterize performance in terms of optical alignment, fluorescence and light scatter resolution, and sensitivity. Finally, suggestions follow for analyzing particles used for calibration. © 2017 by John Wiley & Sons, Inc.

Identification of a suitable internal control for fluorescence analysis on canine peripheral blood samples

Reliable detection of fluorescence intensity (FI) by flow cytometry (FC) is fundamental. FI depends on instrument settings and sample processing procedures: thus, measurements should be done using internal controls with known FI. Commercially available beads-based standards are expensive, thus reducing their usability in the veterinary practice. Cell subsets with stable mean FI (MFI) within the population have been proposed as acceptable surrogates in human medicine. In veterinary medicine, no data exist about stability of antigen expression among different subjects or upon sample storage. The aim of the present study was to evaluate MFI variability of main lymphocytes antigens among the lymphoid cells within each subject, among different subjects, and upon 24-h storage, in order to identify the antigen most suitable as stable internal control in MFI analyses. Peripheral blood samples from 18 healthy dogs were analysed by FC within 3h from sampling to assess the expression of CD3, CD5, CD4, CD8, CD21 and cyCD79b using conjugated monoclonal antibodies. Analyses were restricted to the lymphoid population. Fluorescent microbeads were added to each tube, and antigen MFI was calculated as Relative Fluorescence Intensity RFI (CD/beads). Fluorescence histogram CV (fhCV) for each CD was regarded as an index of the variability of expression among lymphocytes within each subject (cell-to-cell variability); whereas the CV of RFI was regarded as an index of inter-subjects variability (dog-to-dog variability). In 11 cases, FC analyses were repeated after 24h storage at 4°C and RFI and CVs of fresh and stored samples were compared to assess variability linked to storage. CD4 was identified as the best antigen to be used as an internal control for MFI analyses in canine peripheral blood samples because of low cell-to-cell and dog-to-dog variability, and optimal stability upon 24-h storage. Blood samples from a second group of 21 healthy dogs were labelled only with CD4, in order to assess the influence of breed, sex and age on the expression of CD4 in a larger case series. Based on univariate GLMs, none of these variables influenced CD4 RFI. Normalizing fluorescence data using lymphoid CD4 MFI as a reference would improve the comparison of results obtained by different laboratories, patients or times in diagnostic and research analyses of FI. Further studies are needed to confirm our results with different FC approaches.

Use of internal control T-cell populations in the flow cytometric evaluation for T-cell neoplasms

OBJECTIVES

Flow cytometry is an important tool for identification of neoplastic T-cells, but immunophenotypic abnormalities are often subtle and must be distinguished from nonneoplastic subsets. Use of internal control (IC) T-cells in the evaluation for T-cell neoplasms was explored, both as a quality measure and as a reference for evaluating abnormal antigen expression.

METHODS

All peripheral blood specimens (3-month period), or those containing abnormal T-cells (29-month period), stained with CD45 V500, CD2 V450, CD3 PE-Cy7, CD7 PE, CD4 Per-CP-Cy5.5, CD8 APC-H7, CD56 APC, CD16&57 FITC, were evaluated. IC T-cells were identified (DIVA, BD Biosciences) and median fluorescence intensity (MFI) recorded. Selected files were merged and reference templates generated (Infinicyt, Cytognos).

RESULTS

IC T-cells were present in all specimens, including those with abnormal T-cells, but subsets were less well-represented. IC T-cell CD3 MFI differed between instruments (p = 0.0007) and subsets (p < 0.001), but not specimen categories, and served as a longitudinal process control. Merged files highlighted small unusual IC-T subsets: CD2+(dim) (0.25% total), CD2- (0.03% total). An IC reference template highlighted neoplastic T-cells, but was limited by staining variability (IC CD3 MFI reference samples different from test (p = 0.003)).

CONCLUSIONS

IC T-cells present in the majority of specimens can serve as positive and longitudinal process controls. Use of IC T-cells as an internal reference is limited by variable representation of subsets. Analysis of merged IC T-cells from previously analyzed patient samples can alert the interpreter to less-well-recognized non-neoplastic subsets. However, application of a merged file IC reference template was limited by staining variability. © 2016 Clinical Cytometry Society.

Dynamic quantification of antigen molecules with flow cytometry

Traditional methods for estimating the number of expressed molecules, based on the detection of target antigens bound with fluorescently labeled antibodies, assume that the antigen-antibody reaction reaches equilibrium. A calibration procedure is used to convert the intensity of the fluorescence signal to the number of target molecules. Along with the different limitations of every calibration system, this substantially limits the applicability of the traditional approaches especially in the case of low affinity antibodies. We address this problem here with studies in which we demonstrate a new approach to the antigen molecule quantification problem. Instead of using a static calibration system, we analyzed mean fluorescence values over time by flow cytometry during antibody-antigen binding. Experimental data obtained with an LSRII cytometer were fitted by a diffusion-reaction mathematical model using the Levenberg-Marquardt nonlinear least squares curve-fitting algorithm in order to obtain the number of target antigen molecules per cell. Results were compared with the Quanti-BRITE calibration system. We conclude that, instead of using experiment-specific calibration, the value of the binding rate constant for each particular antibody-antigen reaction can be used to quantify antigen molecules with flow cytometry. The radius of CD8 antibody molecule binding site was found, that allows recalculating the binding rate constant for other conditions (different sizes of reagent molecules, fluorescent label, medium viscosity and temperature). This approach is independent of specially prepared calibration beads, antibody reagents and the specific dye and can be applied to both low and high affinity antibodies, under both saturating and non-saturating binding conditions. The method was demonstrated on a human blood sample dataset investigating CD8α antigen on T cells in stable binding conditions.

Validation of cell-based fluorescence assays: practice guidelines from the ICSH and ICCS - part III - analytical issues

Clinical diagnostic assays, may be classified as quantitative, quasi-quantitative or qualitative. The assay's description should state what the assay needs to accomplish (intended use or purpose) and what it is not intended to achieve. The type(s) of samples (whole blood, peripheral blood mononuclear cells (PBMC), bone marrow, bone marrow mononuclear cells (BMMC), tissue, fine needle aspirate, fluid, etc.), instrument platform for use and anticoagulant restrictions should be fully validated for stability requirements and specified. When applicable, assay sensitivity and specificity should be fully validated and reported; these performance criteria will dictate the number and complexity of specimen samples required for validation. Assay processing and staining conditions (lyse/wash/fix/perm, stain pre or post, time and temperature, sample stability, etc.) should be described in detail and fully validated.

Cell separation: Terminology and practical considerations

Cell separation is a powerful tool in biological research. Increasing usage, particularly within the tissue engineering and regenerative medicine communities, means that researchers from a diverse range of backgrounds are utilising cell separation technologies. This review aims to offer potential solutions to cell sorting problems and to clarify common ambiguities in terminology and experimental design. The frequently used cell separation terms of 'purity', 'recovery' and 'viability' are discussed, and attempts are made to reach a consensus view of their sometimes ambiguous meanings. The importance of appropriate experimental design is considered, with aspects such as marker expression, tissue isolation and original cell population analysis discussed. Finally, specific technical issues such as cell clustering, dead cell removal and non-specific antibody binding are considered and potential solutions offered. The solutions offered may provide a starting point to improve the quality of cell separations achieved by both the novice and experienced researcher alike.

Comparative quantitative analysis of cluster of differentiation 45 antigen expression on lymphocyte subsets

Background

Since the recent introduction of radioimmunotherapy (RIT) using antibodies against cluster of differentiation (CD) 45 for the treatment of lymphoma, the clinical significance of the CD45 antigen has been increasing steadily. Here, we analyzed CD45 expression on lymphocyte subsets using flow cytometry in order to predict the susceptibility of normal lymphocytes to RIT.

Methods

Peripheral blood specimens were collected from 14 healthy individuals aged 25-54 yr. The mean fluorescence intensity (MFI) of the cell surface antigens was measured using a FACSCanto II system (Becton Dickinson Bioscience, USA). MFI values were converted into antibody binding capacity values using a Quantum Simply Cellular microbead kit (Bangs Laboratories, Inc., USA).

Results

Among the lymphocyte subsets, the expression of CD45 was the highest (725,368±42,763) on natural killer T (NKT) cells, 674,030±48,187 on cytotoxic/suppressor T cells, 588,750±48,090 on natural killer (NK) cells, 580,211±29,168 on helper T (Th) cells, and 499,436±21,737 on B cells. The Th cells and NK cells expressed a similar level of CD45 (P=0.502). Forward scatter was the highest in NKT cells (P<0.05), whereas side scatter differed significantly between each of the lymphocyte subsets (P<0.05). CD3 expression was highest in the Th and NKT cells.

Conclusions

NKT cells express the highest levels of CD45 antigen. Therefore, this lymphocyte subset would be most profoundly affected by RIT or pretargeted RIT. The monitoring of this lymphocyte subset during and after RIT should prove helpful.

Quantitative flow cytometric analysis of membrane antigen expression

Immunological analysis for cell antigens has been performed by flow cytometry in a qualitative fashion for over thirty years. During that time it has become increasingly apparent that quantitative measurements such as number of antigens per cell provide unique and useful information. This unit on quantitative flow cytometry (QFCM) describes the most commonly used protocols, both direct and indirect, and the major methods of analysis for the number of antibody binding sites on a cell or particle. Practical applications include detection of antigen under- or overexpression in hematological malignancies, distinguishing between B cell lymphoproliferative disorders, and precise diagnosis of certain rare diseases.

Optimization of antibody binding to FcgammaRIIa enhances macrophage phagocytosis of tumor cells

The contribution of Fc-mediated effector functions to the therapeutic efficacy of some monoclonal antibodies has motivated efforts to enhance interactions with Fcgamma receptors (FcgammaR). Although an early goal has been enhanced FcgammaRIIIa binding and natural killer (NK) cell antibody-dependent cell-mediated cytotoxicity (ADCC), other relevant cell types such as macrophages are dependent on additional activating receptors such as FcgammaRIIa. Here, we describe a set of engineered Fc variants with diverse FcgammaR affinities, including a novel substitution G236A that provides selectively enhanced binding to FcgammaRIIa relative to FcgammaRIIb. Variants containing this substitution have up to 70-fold greater FcgammaRIIa affinity and 15-fold improvement in FcgammaRIIa/FcgammaRIIb ratio and mediate enhanced phagocytosis of antibody-coated target cells by macrophages. Specific double and triple combination variants with this substitution are simultaneously capable of exhibiting high NK-mediated ADCC and high macrophage phagocytosis. In addition, we have used this unique set of variants to quantitatively probe the relative contributions of individual FcgammaR to effector functions mediated by NK cells and macrophages. These experiments show that FcgammaRIIa plays the most influential role for macrophages and, surprisingly, that the inhibitory receptor FcgammaRIIb has little effect on effector function. The enhancements in phagocytosis described here provide the potential to improve the performance of therapeutic antibodies targeting cancers.

Quantification of the CBD-FITC conjugates surface coating on cellulose fibres

Background

Cellulose Binding Domains (CBD) were conjugated with fluorescein isothiocyanate (FITC). The surface concentration of the Binding Domains adsorbed on cellulose fibres was determined by fluorescence image analysis.

Results

For a CBD-FITC concentration of 60 mg/L, a coating fraction of 78% and 110% was estimated for Portucel and Whatman fibres, respectively. For a saturating CBD concentration, using Whatman CF11 fibres, a surface concentration of 25.2 × 10^-13 mol/mm² was estimated, the equivalent to 4 protein monolayers. This result does not imply the existence of several adsorbed protein layers.

Conclusion

It was verified that CBDs were able to penetrate the fibres, according to confocal microscopy and TEM-immunolabelling analysis. The surface concentration of adsorbed CBDs was greater on amorphous fibres (phosphoric acid swollen) than on more crystalline ones (Whatman CF11 and Sigmacell 20).

Discrepancy in measuring CD4 expression on T-lymphocytes using fluorescein conjugates in comparison with unimolar CD4-phycoerythrin conjugates

BACKGROUND

Numerous methods for quantitative fluorescence calibration (QFC) have been developed to quantify receptor expression on lymphocytes. However, the results from the use of these different QFC methods vary considerably in the literature. To better identify the causes of these discrepancies, we measured CD4 expression using FITC and phycoerythrin (PE) conjugates to stain CYTO-TROL Control Cells and T-lymphocytes in whole blood and isolated cell preparations. We further examined pH of the cellular microenvironment as a cause of discordant results obtained with the FITC conjugate.

METHODS

Calibration with Quantibrite PE-labeled microspheres and the use of unimolar CD4-PE conjugates provided direct measurement of the antibody bound per cell value (ABC) for CD4 expression on normal T-lymphocytes. Calibration for CD4-FITC monoclonal antibody (Mab) labeled CYTO-TROL Control Cells and normal T-lymphocytes was based on molecules of equivalent soluble fluorochrome (MESF) as determined by FITC-labeled microspheres traceable to NIST RM 8640. The MESF value for CD4-FITC Mab was determined that enabled the conversion of the MESF values obtained for CYTO-TROL cells to ABC. We investigated the likely pH change in the fluorescein microenvironments within FITC-labeled Mab and cells stained with FITC-labeled Mab using a pH sensitive indicator.

RESULTS

The mean ABC value for T-lymphocytes prepared from fresh whole blood using CD4-PE conjugate (48,321) was consistent with previous results, and it was much higher than the mean ABC using CD4-FITC Mab (22,156). The mean ABC value for CYTO-TROL cells using CD4-PE conjugate (43,090) was also higher than that using CD4-FITC conjugate (34,734), although the discrepancy was not as great. Further studies suggested the discrepancy in CYTO-TROL results may be accounted for by the low pH of the membrane microenvironment, but the greater discrepancy in T-lymphocytes could not be fully explained.

CONCLUSION

CD4 expression on fresh normal whole blood samples and CYTO-TROL cells can be consistently quantified in ABC units using Quantibrite PE quantification beads and unimolar CD4-PE conjugates. Quantification with CD4-FITC conjugate is not as consistent, but may be improved by the use of CD4 T-cells as biological calibrators. This approximation is valid only for surface receptors with consensus ABC values measured by different QFC methods serving as biological standards.

Quantitative analysis of the expression of glycosylphosphatidylinositol-anchored proteins during the maturation of different hematopoietic cell compartments of normal bone marrow

BACKGROUND

Glycosylphosphatidylinositol-anchored proteins (GPI-AP) are a heterogeneous group of proteins deficiently expressed in patients with paroxysmal nocturnal hemoglobinuria. Up till now, no study has been reported in which the exact patterns of expression of a large number of GPI-AP are quantitatively evaluated in normal bone marrow (BM) cells classified according to their lineage and maturation stage.

METHODS

In the present study, we have quantitatively analyzed the expression of eleven different GPI-AP (CD14, CD16, CD24, CD48, CD52, CD58, CD59, CD66b, CD87, CD109 and CD157) during maturation of the neutrophil, monocytic, erythroid, lymphoid, basophil and plasmacytoid dendritic cells (DC) lineages in normal BM as a frame of reference for the understanding of the abnormal patterns of expression of GPI-AP observed in the BM of PNH patients.

RESULTS

Our results show that expression of most GPI-AP varies during normal BM maturation, different profiles being frequently observed depending on the cell lineage or the GPI-AP analyzed.

CONCLUSION

Overall, these results provide a detailed map GPI-AP expression during normal hematopoietic differentiation, which could serve as a basis for the identification and characterization of changes occurring in PNH.

Performance of calibration standards for antigen quantitation with flow cytometry in chronic lymphocytic leukemia

BACKGROUND

The fluorescence intensities of CD3, CD4 on T cells and CD20, CD22 molecules on B cells were quantitatively measured on lymphocytes from chronic lymphocytic leukemia (CLL) patients and healthy donors.

METHODS

The performance of three different types of microbeads was compared, i.e. Quantum molecules of equivalent soluble fluorochrome (Q-MESF), Quantum simply cellular (QSC), and QuantiBRITE (QB). As all PE-conjugates had a F/P ratio of 1:1, the MESF units represented also the antibody binding capacity (ABC).

RESULTS

The ABCs of CD4 and CD20 antigens estimated with QSC (ABC(QSC)) were higher than those assigned with QB (ABC(QB)) with an average difference 49%. Higher numbers of antigenic sites were obtained with Q-MESF than with QSC for CD20 antigen. On the contrary, CD4 antigenic sites numbers estimated with QSC were higher than those estimated with Q-MESF. ABC values estimated with Quantum MESF PE (ABC(Q-MESF)) were approximately 15% higher than ABC(QSC), whereas ABC(Q-MESF) was approximately 49% higher than ABC(QB). Statistically significant correlations were found between the values obtained using various standards. The present study is the first to report down-regulation of CD3 antigen on T cells from patients with CLL.

CONCLUSIONS

This study emphasizes the relevance of quantitative measurement of fluorescence intensity by flow cytometry as a standardized approach to measure and interpret the expression of some CLL markers and reduce variability of results obtained at different sites in multi-center clinical studies.

Normal patterns of expression of glycosylphosphatidylinositol-anchored proteins on different subsets of peripheral blood cells: A frame of reference for the diagnosis of paroxysmal nocturnal hemoglobinuria

BACKGROUND

Evaluation of the expression of glycosylphosphatidylinositol-anchored membrane proteins (GPI-AP) is currently used for the diagnosis of paroxysmal nocturnal hemoglobinuria (PNH). In this study, we analyzed the amount of expression of a wide variety of GPI-AP in different subsets of hematopoietic cells present in normal peripheral blood (PB), to establish their normal patterns of expression and provide a frame of reference for the definition of the best combination of GPI-AP and PB cell subsets to be applied in the diagnosis and monitoring of PNH.

RESULTS

Our results show variable patterns of expression of different GPI-AP in distinct subsets of normal PB cells. Combined use of CD55 and CD59 represented the most useful dual-marker combination; however, its utility remained suboptimal for several subsets of leukocytes and for platelets.

CONCLUSIONS

For some cell subsets such as the neutrophils additional useful markers could be selected from a relatively broad panel (CD16/CD24/CD55/CD59/CD66b/CD157), whereas for other cell subsets the number of useful antigens was either restricted (monocytes: CD14/CD55/CD157; B cells: CD24/CD48/CD52/CD55; CD4+ T cells: CD48/CD52/CD55; eosinophils: CD55/CD59; CD8+ T cells: CD48/CD55) or limited to a single marker (CD48 on CD56low NK cells, CD55 on BDCA3- dendritic cells and CD56high NK cells, and CD59 for red cells), from all antigens analyzed.

Role of low CD4 levels in the influence of human immunodeficiency virus type 1 envelope V1 and V2 regions on entry and spread in macrophages

Human immunodeficiency virus type 1 (HIV-1) isolates vary in their ability to infect macrophages. Previous experiments have mapped viral determinants of macrophage infectivity to the V3 hypervariable region of the HIV-1 envelope glycoprotein. In our earlier studies, V1 and V2 sequences of HIV-1 were also shown to alter the ability of virus to spread in macrophage cultures, whereas no effect was seen in lymphocyte cultures. In the present study, determinants that allowed certain HIV-1 clones to infect and spread in macrophages were primarily mapped to the V2 region and were found to act by influencing early events of viral infection. By an assay of viral entry into macrophages, it was shown that viruses with the V2 region from the Ba-L strain of HIV-1 had >10-fold-higher entry efficiency than viruses with the V2 region derived from the NL4-3 strain. V1 region differences between these groups caused a twofold difference in entry. The known low expression of CD4 on macrophages appeared to be important in this process. In entry assays conducted with HeLa cell lines expressing various levels of CD4 and CCR5, low levels of CD4 influenced the efficiency of entry and fusion which were dependent on viral V1 and V2 envelope sequences. In contrast, no effect of V1 or V2 was seen in HeLa cells expressing high levels of CD4. Thus, the limited expression of CD4 on macrophages or other cell types could serve as a selective factor for V1 and V2 envelope sequences, and this selection could in turn influence many aspects of AIDS pathogenesis in vivo.

Mechanisms of nonrandom human immunodeficiency virus type 1 infection and double infection: preference in virus entry is important but is not the sole factor

We previously demonstrated that human immunodeficiency virus type 1 (HIV-1) infection is nonrandom and that double infection occurs more frequently than predicted from random events. To probe the possible mechanisms for nonrandom infection, we examined the role of HIV-1 entry pathways by using viruses pseudotyped with either CCR5-tropic HIV-1 Env or vesicular stomatitis virus G protein (VSV G). These two proteins use different receptors and entry pathways. We found that regardless of the protein used, double infection occurred more frequently than random events, indicating nonrandom HIV-1 infection in both entry pathways. However, the frequency of double infection differed significantly, depending on the envelope protein. In primary CD4(+) T cells, double infection occurred most frequently when both viruses had CCR5-tropic HIV-1 Env and least frequently when the two viruses had different envelopes. These results indicated that the preference in virus entry was a significant but not the only factor contributing to nonrandom double infection. Furthermore, we demonstrated that the CD4 expression level in primary T cells affects their susceptibility to CCR5-tropic HIV-1 infection but not VSV G-pseudotyped HIV-1 infection. We have also examined infection with two viruses pseudotyped with CCR5- or CXCR4-tropic HIV-1 Env and have found that double infection occurred more frequently than random events. These results indicate that coreceptor usage is not a barrier to recombination between the two virus populations. In our previous study, we also demonstrated nonrandom double infection via dendritic cell (DC)-mediated HIV-1 transmission. To test our hypothesis that multiple HIV-1 virions are transmitted during DC-T-cell contact, we used two populations of DCs, each capturing one vector virus, and added both DC populations to T cells. We observed a decreased frequency of double infection compared with experiments in which DCs captured both viruses simultaneously. Therefore, these results support our hypothesis that multiple virions are transmitted from DCs to T cells during cell-mediated HIV-1 transmission.

Expression profiling by high-throughput immunohistochemistry

Immunohistochemistry (IHC) provides valuable information on expression of proteins within tissues at a cellular and subcellular level. Recent developments in the practice of IHC now make it possible to contemplate using this technique as a high-throughput expression profiling system. Advances have been made in creation and use of tissue microarrays, in automated IHC and in image capture/analysis. Each of these technologies are reviewed and issues surrounding their use considered. The success of high-throughput IHC is also dependent on both generation and screening of appropriate antibodies. Antibody-related issues which are likely to affect the success of high-throughput IHC, such as specificity, sensitivity, fixation choice, etc., are also considered.

DNA immunization with HIV early genes in HIV type 1-infected patients on highly active antiretroviral therapy

The aim of this study was to evaluate the immunological responses induced by DNA plasmids containing HIV regulatory genes administered in combination in HIV-1-infected patients with pretreatment with highly active antiretroviral treatment (HAART). The study is a double-blind, randomized, and placebo-controlled study, including 15 asymptomatic HIV-1-infected patients on stable HAART for at least 6 months and with plasma HIV RNA levels below 50 copies/ml. Ten patients received a combination of rev, tat, and nef intramuscularly (im) at weeks 0, 4, and 16 at increasing doses giving totals of 300 (100 x 3), 900 (300 x 3), and 1800 (600 x 3) micrograms DNA. Five patients received saline in the same amounts im. Antigen-specific cytotoxic T lymphocyte (CTL) levels were preserved or increased and new T lymphocyte proliferative responses were induced in the group immunized with the HIV DNA genes. No increase in antibody levels was noted. Despite a 10-fold higher vaccine dose, patients on HAART did not respond better to vaccination compared to non-HAART patients included in a previous study where the genes were administered separately. Combining the regulatory genes rev, tat, and nef in increasing doses may reduce the anticipated augmentation of HIV-specific T cell proliferative and CTL responses. Viral suppression did not seem to further improve the initial vaccine responses of patients with comparable CD4 levels.

A standardized procedure for quantitation of CD11b on polymorphonuclear neutrophil by flow cytometry: potential application in infectious diseases

An up-regulation of the surface marker CD11b has been demonstrated during polymorphonuclear (PMN) cell activation. CD11b over-expression is often associated with inflammation and is considered as an early marker of infection. However, the absence of standardized assay and the variability of preanalytical settings leading to PMN artifactual activation have compromised the interest of this marker. In the present study a standardized quantitative flow cytometry assay directly performed in whole blood has been used to determine CD11b expression on PMN cells. The results indicate that quantitative flow cytometry can provide consistent CD11b density values between laboratories provided that a calibration system is used including specific calibrators, reagents and protocols. This method allowed us to evidence an up-regulation of CD11b expression for infected patients. This quantitation is a standardized and potentially useful method in clinical situations implying quantitative CD11b expression variations.

Leukocytes, cytokines, growth factors and hormones in human skeletal muscle and blood after uphill or downhill running

Muscular adaptation to physical exercise has previously been described as a repair process following tissue damage. Recently, evidence has been published to question this hypothesis. The purpose of this study was to investigate inflammatory processes in human skeletal muscle and epimysium after acute physical exercise with large eccentric components. Three groups of subjects (n= 19) performed 45 min treadmill running at either 4 deg (n= 5) or 8 deg (n= 9) downhill or 4 deg uphill (n= 5) and one group served as control (n= 9). One biopsy was taken from each subject 48 h post exercise. Blood samples were taken up to 7 days post exercise. Compared to the control group, none of the markers of inflammation in muscle and epimysium samples was different in any exercised group. Only subjects in the Downhill groups experienced delayed onset of muscle soreness (DOMS) and increased serum creatine kinase activity (CK). The detected levels of immunohistochemical markers for T cells (CD3), granulocytes (CD11b), leukaemia inhibitory factor (LIF) and hypoxia-inducible factor 1beta (HIF-1beta) were greater in epimysium from exercised subjects with DOMS ratings >3 (0-10 scale) compared to exercised subjects without DOMS but not higher than controls. Eccentric physical exercise (downhill running) did not result in skeletal muscle inflammation 48 h post exercise, despite DOMS and increased CK. It is suggested that exercise can induce DOMS by activating inflammatory factors present in the epimysium before exercise. Repeated physical training may alter the content of inflammatory factors in the epimysium and thus reduce DOMS.

Immune system alteration in response to two consecutive soccer games

AIM

Changes in leucocyte and monocyte subpopulations were investigated in 10 elite male soccer players aged 16-19 years. The purpose was to perform a descriptive study of immunological alterations in elite soccer players in response to two consecutive games separated by 20 h. It was hypothesized that in response to two games the players would show signs of short-term immunosuppression.

METHODS

Blood samples were taken before the first soccer game, immediately after the second game and after 6, 24, 48 and 72 h. Cell surface antigens, testosterone and cortisol were investigated.

RESULTS

During the first 6 h after the second game there was a significant increase in number of circulating neutrophils, mature (CD20+ CD5+) B cells and CD4/CD8 ratio. A significant decrease was observed in the number of natural killer (NK) cells, monocytes and adhesion on lymphocytes and monocytes. In a delayed phase, 48 h after the second game the expression of both adhesion and signalling molecules increased on lymphocytes and monocytes. Changes in adhesion and signalling molecules at 48 h correlated negatively to the subjects VO2max, suggesting larger immunological response to similar exercise in subjects with lower aerobic exercise capacity.

CONCLUSION

In response to competitive soccer exercise some immunological variables are enhanced while others are depressed. Observed changes may serve a purpose in adaptation to exercise by signalling via adhesion.

Performance evaluation of QuantiBRITE phycoerythrin beads

BACKGROUND

The performance of QuantiBRITE phycoerythrin (PE) beads to standardize quantitation in terms of antibodies bound per cell (ABC) was evaluated by measuring precision, variation across multiple instruments, and variation across time.

METHODS

For CD4 quantitation, whole blood was stained with a two-color CD4 reagent using a no-wash/no-lyse format. For CD69 quantitation, whole blood was activated with either phorbol myristate acetate (PMA) or CD3 beads and then stained with a three-color CD69 reagent using a lyse-no-wash format.

RESULTS

Across 20 normal donors, the mean CD4 ABC was 51,000. Within-assay precision on quantitation of CD4 ABC on T cells had a coefficient of variance (CV) of <1.0%. Across multiple flow cytometers, quantitation of CD4 ABC had a CV of <5.0%. Within-donor CV on CD4 ABC on 20 donors across 2 months ranged from 1.3% to 3.2%. Within-assay precision on quantitation of CD69 on T cells activated with either PMA or CD3 beads had a CV of <3.0%. Within-donor CV of CD69 ABC across 1 month ranged from 2% to 18% on PMA-activated samples and from 7% to 24% on CD3 bead-activated samples.

CONCLUSIONS

Our results indicate that the QuantiBRITE PE beads provide a useful tool for standardized analysis across labs. When used in conjunction with 1:1 conjugates of PE-to-monoclonal antibody, the QuantiBRITE PE beads provide a simple yet robust means of quantitating expression levels in terms of ABC.

CCR5 and CXCR4 expression correlated with X4 and R5 HIV-1 infection yet not sustained replication in Th1 and Th2 cells

OBJECTIVE

To investigate the infectivity of T-helper (Th)1 and Th2 cells (derived from ccr5 wild-type and homozygous ccr5 Delta 32) to R5 and X4 HIV-1.

DESIGN

It remains unclear whether infection of Th1 and Th2 CD4 cells by R5 and X4 viruses mirrors their co-receptor expression profile as no direct quantitation of coreceptor levels and infection has been performed. In addition, it is unknown whether the lack of CCR5 expression affects the degree of Th1/Th2 polarization.

METHODS

Surface expression of CCR5 and CXCR4 was determined by quantitative fluorescence activated cell sorter analysis on in vitro differentiated Th1 and Th2 cells. R5 (Ba-L) and X4 (IIIB) HIV-1 isolates were used for infection studies and the efficiency of viral entry was determined by quantitative real time polymerase chain reaction detection of reverse transcribed proviral DNA.

RESULTS

Cell surface density of CCR5 molecules was eight-fold higher in Th1 versus Th2 subsets (P = 0.005) whereas CXCR4 surface density was four-fold higher in Th2 versus Th1 subsets (P = 0.006). Preferential infection and entry of Th1 cells by R5 HIV-1 was not associated with preferential replication, as eventually the R5-virus replicated to a higher level in Th2 cells in spite of lower initial viral infection/entry. By contrast, Th2 cells preferentially supported X4-virus infection and replication. High beta chemokine secretion by Th1 cells was associated with a lower R5 replication rate.

CONCLUSIONS

Th1 and Th2 cells differ in their infection efficiency for R5 and X4 HIV-1. ccr5 Delta 32-homozygous individuals maintain the ability for Th1/Th2 polarization, i.e., the expression of CCR5 is not required for Th1/Th2 polarization.

Inhibition of activated/memory (CD45RO(+)) T cells by oxidative stress associated with block of NF-kappaB activation

Impaired immune responses in cancer patients have been associated with oxidative stress. Increased levels of reactive oxygen species released from activated, tumor-infiltrating macrophages or granulocytes may therefore constitute a hurdle for effective immunotherapy against cancer. In this study, we investigated functional consequences and molecular events in T cells exposed to low levels of oxidative stress. We observed that cytokine production of human PBMC, upon stimulation with an HLA-A*0201-restricted influenza peptide and nonspecific receptor cross-linking, was reduced after exposure to micromolar levels of H2O2. Functional impairment as measured by IFN-gamma release occurred earlier and at lower doses of exogenously added H2O2 than required to induce apoptosis. This suggests that there is a dose window of oxidative stress leading to T cell unresponsiveness in the absence of apoptosis. The reduction of Th1 cytokines, induced by H2O2, was predominantly observed in memory/effector (CD45RO(+)) T cells and correlated with a block in NF-kappaB activation. IL-10 production was more profoundly influenced by low doses of H2O2 than IFN-gamma, TNF-alpha, and IL-2. The influence of H2O2 on production of IL-10 was not significantly different between memory/activated and naive T cells. These observations suggest that Th1 and Th2 cytokines are differently regulated under conditions of oxidative stress. Taken together, these findings may explain why Ag-experienced, CD45RO(+), T cells found in the tumor milieu are functionally suppressed.

Assay of spherical cell surface molecules by thermal lens microscopy and its application to blood cell substances

To detect and quantitate uneven cell surface molecules, such as blood group antigens on a blood cell and immunoglobulin molecules on a mast cell, an improved method of thermal lens microscopy was employed. The antigen molecules were immunologically stained with their antibodies, which were labeled with colloidal gold. Since the surface of the biological cells was not flat but spherical, the focal point of the probe laser beam inevitably deviated from the sample surface on the moving stage. Therefore, the deviation of the focal point of the probe beam was corrected by adjusting the phase of the signal. Using this technique, a three-dimensional antigen distribution on each cell surface was imaged. Despite the convex surface of cells, labeled colloidal gold was correctly quantified. In the measurement of erythrocyte antigens, a small quantity of Lewis antigens was successfully detected on the umbilical cord erythrocytes. Immunoglobulin E on a mast cell, derived from the allergic human mucosa fungus, was also observed by this method, and the distribution of IgE molecules on the cell surface was quantitatively imaged. A thermal lens microscope, which measures spherical samples correcting the deviation, made it possible for us to observe and assay the substances on biological specimens that have complicated forms, such as living cells in vivo or in situ.

Clinical and immunological benefits from highly active antiretroviral therapy in spite of limited viral load reduction in HIV type 1 infection

Both naive and memory T lymphocyte responses are lost during advanced HIV infection. Treatment with highly active antiretroviral therapy (HAART) is associated with an increase in T lymphocytes and a reduction in viral load. However, the viral response to HAART in patients with low levels of helper T lymphocytes and a high viral load is often not satisfactory. We investigated the capacity of long-term HAART to reconstitute the immune system in severely ill patients. A nonselected longitudinal patient population with high baseline viral levels and CD4(+) cells below 100 x 10(6)/liter were monitored for 2 years during HAART. Markers to estimate the therapeutic effects included viral levels and cell surface markers representing naive and memory T lymphocytes as well as activation markers, B cells, NK cells, and clinical events. After 2 years of treatment, viral load was reduced to undetectable levels in 55% (viral responders, vRs) and less than 1 log (median value) from baseline in 45% (viral low responders, vLRs). Elevated numbers of memory and naive CD4(+) and CD8(+) cells as well as a decrease in activation markers were seen in both vRs and vLRs. However, the magnitude was greater in vRs. No differences in the clinical outcome were observed between vRs and vLRs. We conclude that most patients, even in advanced stages of HIV disease, benefited from HAART. The magnitude of the response was related to good viral reduction, but even patients with poor viral reduction had a recovery of naive and memory CD4(+) and CD8(+) cells. Even a small reduction in viral load is thus of importance for health and potentially also for years of survival.

Immunological changes in human skeletal muscle and blood after eccentric exercise and multiple biopsies

1. A role of the immune system in muscular adaptation to physical exercise has been suggested but data from controlled human studies are scarce. The present study investigated immunological events in human blood and skeletal muscle by immunohistochemistry and flow cytometry after eccentric cycling exercise and multiple biopsies. 2. Immunohistochemical detection of neutrophil- (CD11b, CD15), macrophage- (CD163), satellite cell- (CD56) and IL-1beta-specific antigens increased similarly in human skeletal muscle after eccentric cycling exercise together with multiple muscle biopsies, or multiple biopsies only. 3. Changes in immunological variables in blood and muscle were related, and monocytes and natural killer (NK) cells appeared to have governing functions over immunological events in human skeletal muscle. 4. Delayed onset muscle soreness, serum creatine kinase activity and C-reactive protein concentration were not related to leukocyte infiltration in human skeletal muscle. 5. Eccentric cycling and/or muscle biopsies did not result in T cell infiltration in human skeletal muscle. Modes of stress other than eccentric cycling should therefore be evaluated as a myositis model in human. 6. Based on results from the present study, and in the light of previously published data, it appears plausible that muscular adaptation to physical exercise occurs without preceding muscle inflammation. Nevertheless, leukocytes seem important for repair, regeneration and adaptation of human skeletal muscle.

Changes in antigen expression on B lymphocytes during HIV infection

Involvement of the B cell compartment during HIV infection plays an important role in the development of immune deficiency. The aim of this study was the identification of specific antigen expression changes on B lymphocytes in HIV infection as surrogate markers in this cell population of certain functional aspects that could be easily measured. We investigated the level of expression of a series of constitutive surface markers in B lymphocytes (HLA-DR, CD19, CD20, CD21, CD22) from 30 HIV-seropositive adult patients and 20 normal controls. By means of quantitative flow cytometry, we assessed the number of antigen molecules per cell using standard beads to convert fluorescence intensity into antibody-binding capacity (ABC). We correlated these results with disease stage and cellular markers of immune activation. The expression of CD20 was significantly increased when B cells from HIV-infected individuals were compared with those from uninfected subjects. No differences were found in the density expression of HLA-DR on activated CD3+ T cells between HIV+ and HIV- subjects. In contrast, B cells from HIV+ patients showed a significantly lower number of HLA-DR molecules per cell compared to normal controls. A significantly lower number of CD21 molecules per cell was also found on B lymphocytes from HIV+ patients compared to normal controls. No differences in CD19 and CD22 expression levels on B cells between HIV-infected patients and controls were detected. No differences between HIV disease stages were detected for CD19, HLA-DR, CD21 and CD22. In contrast, differences between stages were found for CD20 expression, which showed significant changes in individuals with less than 200 CD4 T cells/microl. The data presented here demonstrate that B lymphocytes of HIV-infected individuals exhibit specific changes in receptor density expression during HIV infection and that these changes are often correlated with progression of disease, as measured by CD4 counts. No correlations were found between the percentages of HLA-DR+ T cells and the ABC values of the B cell markers studied. These antigen expression modulations may contribute to the humoral abnormalities during HIV infection and to the development of severe, recurrent or multiple bacterial infections. Therefore, quantitative flow cytometry may be of value in HIV infection both for clinical and biological studies. The study of antigen density changes on B cells in HIV infection may allow a better understanding of the humoral immune defects observed in these patients and provide insights into the functional defects of B cell compartment in HIV-infected individuals.

Detection and measurement of a single blood cell surface antigen by thermal lens microscopy

A highly sensitive method for detection of antigens on the surface of a single blood cell using thermal lens microscopy is described. Colloidal gold, coated with antibody, was used to stain membrane antigens of leukocytes. Human leukocyte antigens on the lymphocytes and mononuclear leukocytes were observed by new thermal lens microscopy, which involves spectrometry using a laser-induced thermal-lens effect. Antigens of HLA-A, -B, and -C loci on the lymphocytes were identified and quantitated using a single cell. The image of HLA-A, -B, and -C antigen distribution on a mononuclear leukocyte was obtained. Our laser microscope, newly devised for measuring convex surface cells, is a powerful analytical tool for detecting and quantitating localized antigens in a single cell and/or cell-surface-associated molecules.

Critical role of enhanced CD4 affinity in laboratory adaptation of human immunodeficiency virus type 1

Strains of human immunodeficiency virus type 1 (HIV-1) that use the coreceptor CXCR4 (X4 strains) become laboratory adapted (LA) when selected for ability to replicate in leukemic T cell lines such as H9. Compared with patient X4 viruses, the gp120-gp41 complexes of LA viruses have a constellation of common properties including enhanced affinities for CD4, greater sensitivities to inactivations by diverse antibodies and by soluble CD4, increased shedding of gp120, and improved abilities to infect HeLa-CD4 cell clones that contain only trace quantities of CD4. These common characteristics, which may result from a concerted structural rearrangement of the gp120-gp41 complexes, have made it difficult to identify a specific feature that is critical for laboratory adaptation. To test the hypothesis that replication of patient X4 HIV-1 is limited by the low CD4 concentration in H9 cells (7.0 x 10(3) CD4/cell), we constructed H9 derivatives that express at least 10 times more of this receptor. Interestingly, most patient X4 isolates readily grew in these derivative cells, and the resulting virus preparations retained the characteristics of primary viruses throughout multiple passages. In contrast, selection of the same viruses in the parental H9 cells resulted in outgrowth of LA derivatives. We conclude that a weak interaction of patient X4 HIV-1 isolates with CD4 is the primary factor that limits their replication in leukemic T cell lines.

Standardization of lymphocyte antibody binding capacity - a multi-centre study

As quantitative flow cytometry is being increasingly used to characterize non-malignant and malignant disorders, interlaboratory standardization becomes an important issue. However, the lack of standardized methods and process controls with predefined antibody binding capacity values, limits direct interlaboratory comparison. The present study has addressed these issues using a stable whole blood product and a standardized antigen quantification protocol. It was demonstrated that: (i) a standard technical protocol can result in a high degree of interlaboratory concordance; (ii) interlaboratory variation of less than 12% can be achieved for CD4 antibody binding capacity values; and (iii) stable whole blood can be used as a process control with predefined antibody binding capacity values. Furthermore, using such an approach, a normal range was established for CD3, CD4 CD8 and CD19. These antigens appear to be expressed in a hierarchical manner, a factor that could be used as a procedural quality control measure.

Molecular quantification of cell cycle-related gene expression at the protein level

BACKGROUND

Immunofluorescence cytometry of antigen and DNA content provides relative measurements of the cell cycle phase distribution of a specific epitope. Measurement of correlated expression of epitopes on signaling and regulatory proteins will be useful in the study of the complex pathways involved in cell cycle regulation and carcinogenesis. However, to formulate regulatory pathway models, measurements of molecules per cell would be more useful than relative measurements of intensity. Here, we report on a system in which the relationship between molecules and fluorescence is determined for a reference set of cell lines that are then used to directly calculate the number of molecules for unknowns. To demonstrate the process, we calculated the cell cycle phase distribution of SV40 large T antigen (Tag) in the reference cells.

METHODS

A set of cell line clones expressing different levels of Tag were isolated. Quantitative Western blots of these cells and purified, recombinant Tag were performed. Cells from the same sample were stained and analyzed by flow cytometry for Tag and DNA. The relationship between molecules and fluorescence was established and calculations were performed for the phase distributions of Tag.

RESULTS

The five cell lines had 0.11, 0.27, 1.06, 2.44, and 2.63 x 10(6) molecules of Tag per cell, determined by Western blot. The average coefficient of variation was 10.6%. The relationship of molecules to fluorescence fit a linear equation (r(2) = 0.96) over the range, 0.11 - 2.63 x 10(6) molecules, however, the same equation did not fit the relationship between 0 molecules, defined by isotype staining controls, and the lowest expressing cell line. To calculate the phase distributions of molecules in the lowest cell line, a second linear equation from 0 to 110,000 molecules was used.

CONCLUSIONS

This work describes a system where fixed cells expressing various levels of a target antigen quantified by Western blots can be used to standardize flow cytometric measurements of gene expression in absolute terms.

Subsets of T-cells and in vitro cytokine production after measles and varicellae-zoster virus antigen stimulation in allogeneic BMT patients

This study was performed to analyse differences in T-cell proliferation induced by a latent virus, varicellae-zoster virus (VZV) and a non-latent virus, measles virus, in patients after allogeneic bone marrow transplantation (BMT). The lymphoproliferative response to measles antigen, VZV-antigen (VZV-ag), and phytohemagglutinin (PHA) was measured by 3H-thymidine incorporation, and interferon-gamma (IFN-gamma) and interleukin-10 (IL-10) analyses in supernatants after in vitro stimulation of peripheral blood mononuclear cells (PBMC) from 22 patients and 18 healthy controls. The cytokine levels were correlated with T-cell subsets by FACS analyses. At the antigen concentrations used, VZV-ag induced higher levels of IFN-gamma (p < 0.05) than did the measles antigen, whereas the levels of IL-10 were similar. Patients without a cell mediated immune (CMI) response to VZV-ag or measles antigen had lower CD4+ T-cell counts than did controls (p < 0.01 in both cases) and lower IFN-gamma production after non-specific PHA stimulation (p <0.01). The IFN-gamma and IL-10 levels after measles antigen stimulation correlated with the number of CD4+ T-cells (p < 0.01 and p < 0.05, respectively), and after VZV-ag mainly to the number of CD8+ T-cells (p < 0.01 and p < 0.05, respectively). These results suggest that there is a difference in the types of T-cells that respond to VZV-ag and measles antigen stimulation, respectively. The impaired CMI response to viral antigens seen in many patients may be explained both by a low number of CD4+ T-cells and by a cell dysfunction.

Quantification of CD4, CCR5, and CXCR4 levels on lymphocyte subsets, dendritic cells, and differentially conditioned monocyte-derived macrophages

CCR5 and CXCR4 are the major HIV-1 coreceptors for R5 and X4 HIV-1 strains, respectively, and a threshold number of CD4 and chemokine receptor molecules is required to support virus infection. Therefore, we used a quantitative fluorescence-activated cell sorting assay to determine the number of CD4, CCR5, and CXCR4 antibody-binding sites (ABS) on various T cell lines, T cell subsets, peripheral blood dendritic cells (PBDC), and monocyte-derived macrophages by using four-color fluorescence-activated cell sorting analysis on fresh whole blood. Receptor levels varied dramatically among the various subsets examined and typically varied from 2- to 5-fold between individuals. CCR5 was expressed at much higher levels in CD4+/CD45RO+/CD62L-true memory cells compared with CD4+/CD45RO+/CD62L+ cells. Fresh PBDC had the highest number of CCR5 ABS among the leukocyte subsets examined but had few CXCR4 ABS, affording a strategy for sort-purifying PBDC. In vitro maturation of PBDC resulted in median 3- and 41-fold increases in CCR5 and CXCR4 ABS, respectively. We found that macrophage colony-stimulating factor caused the greatest up-regulation of both CCR5 and CXCR4 on macrophage maturation (from approximately 5,000 to approximately 50, 000 ABS) whereas granulocyte-macrophage colony-stimulating factor caused a marked decrease of CXCR4 (from approximately 5,000 ABS to <500) while up-regulating CCR5 expression (from approximately 5,000 to approximately 20,000 ABS). Absolute ABS for CD4 and the major HIV-1 coreceptors serve as a more quantitative measure of cell surface expression, and we propose that this be used for future studies looking at the modulation of CD4 or chemokine receptor expression by cytokines, HIV-1 infection, or receptor polymorphisms.

Effects of eccentric exercise on the immune system in men

The effects of eccentric exercise on changes in numbers of circulating leukocytes, cell activation, cell adhesion, and cellular memory function were investigated in 12 men, aged 22-35 yr. The immunologic effects of postexercise epidermal treatment with monochromatic, infrared light were also evaluated. Blood was drawn before and 6, 24, and 48 h after exercise for phenotyping and analysis of creatine kinase activity. There was an increase in leukocyte, monocyte, and neutrophil number, no change in the number of basophils, eosinophils, B cells, and T cells, and a decrease in natural killer cell number postexercise. Some markers of lymphocyte and monocyte activation remained unchanged or decreased, whereas the expression of adhesion molecules 62L and 11b increased on monocytes. It is concluded that eccentric exercise induced decreased activation, and increased cell adhesion capacity, of monocytes. Altered trafficking of cells between lymphoid tissue and blood, selective apoptosis, or attachment/detachment from the endothelial wall can explain the observed phenotypic changes. Treatment with monochromatic, infrared light did not significantly affect any of the investigated variables. Correlations between immunologic and physiological parameters indicate a role of the immune system in adaptation to physical exercise.

Levels of expression of CD19 and CD20 in chronic B cell leukaemias

AIMS

To investigate whether the antigen levels of the B cell lineage markers CD19 and CD20 can distinguish between normal and neoplastic B cells or characterise distinct expression patterns among the chronic B cell leukaemias.

METHODS

Peripheral blood cells from 70 patients with B cell disorders and 17 healthy donors were analysed by quantitative flow cytometry. Direct immunofluorescence staining was performed with phycoerythrin conjugated CD19 and CD20 monoclonal antibodies. Standard microbeads with different capacities to bind mouse immunoglobulins were used to convert the mean fluorescence intensity (MFI) values into number of antigen molecules/cell, expressed as antibody binding capacity (ABC).

RESULTS

CD19 and CD20 ABC values in leukaemic B cells differed from those of normal blood B lymphocytes. The results identified distinct profiles of CD19 and CD20 expression in the various types of B cell leukaemias. In all leukaemias studied except hairy cell leukaemia (HCL), CD19 expression was significantly lower than the mean (SD) value in normal B cells (22 (7) x 10(3) molecules/cell), as follows: chronic lymphocytic leukaemia (CLL), 13 (7) x 10(3); B prolymphocytic leukaemia (B-PLL), 16 (9) x 10(3); splenic lymphoma with villous lymphocytes (SLVL), 15 (11) x 10(3); mantle cell lymphoma (MCL), 10 (7) x 10(3). In HCL there was strong CD19 expression (38 (16) x 10(3)). In contrast, the level of expression of membrane CD20 was higher than the mean (SD) value in normal B cells (94 (16) x 10(3) molecules/cell) in MCL (123 (51) x 10(3)); B-PLL (129 (47) x 10(3)); SLVL (167 (72) x 10(3)); and HCL (312 (110) x 10(3)); while it was significantly lower (65 (11) x 10(3)) in CLL compared with normal B cells and the other B cell leukaemias.

CONCLUSIONS

Quantitative determination of CD19 and CD20 may provide useful diagnostic information for the study of B lymphoproliferative disorders.