Comparison of four lymphocyte isolation methods applied to rodent T cell subpopulations and B cells

Fully-automated and field-deployable blood leukocyte separation platform using multi-dimensional double spiral (MDDS) inertial microfluidics

A fully-automated and portable leukocyte separation platform was developed based on a new type of inertial microfluidic device, multi-dimensional double spiral (MDDS) device, as an alternative to centrifugation. By combining key innovations in inertial microfluidic device designs and check-valve-based recirculation processes, highly purified and concentrated WBCs (up to >99.99% RBC removal, ∼80% WBC recovery, >85% WBC purity, and ∼12-fold concentrated WBCs compared to the input sample) were achieved in less than 5 minutes, with high reliability and repeatability (coefficient of variation, CV < 5%). Using this, one can harvest up to 0.4 million of intact WBCs from 50 μL of human peripheral blood (50 μL), without any cell damage or phenotypic changes in a fully-automated operation. Alternatively, hand-powered operation is demonstrated with comparable separation efficiency and speed, which eliminates the need for electricity altogether for truly field-friendly sample preparation. The proposed platform is therefore highly deployable for various point-of-care applications, including bedside assessment of the host immune response and blood sample processing in resource-limited environments.

Immune cell subsets and their gene expression profiles from human PBMC isolated by Vacutainer Cell Preparation Tube (CPT™) and standard density gradient

Background

High quality genetic material is an essential pre-requisite when analyzing gene expression using microarray technology. Peripheral blood mononuclear cells (PBMC) are frequently used for genomic analyses, but several factors can affect the integrity of nucleic acids prior to their extraction, including the methods of PBMC collection and isolation. Due to the lack of the relevant data published, we compared the Ficoll-Paque density gradient centrifugation and BD Vacutainer cell preparation tube (CPT) protocols to determine if either method offered a distinct advantage in preparation of PBMC-derived immune cell subsets for their use in gene expression analysis. We evaluated the yield and purity of immune cell subpopulations isolated from PBMC derived by both methods, the quantity and quality of extracted nucleic acids, and compared gene expression in PBMC and individual immune cell types from Ficoll and CPT isolation protocols using Affymetrix microarrays.

Results

The mean yield and viability of fresh PBMC acquired by the CPT method (1.16 × 10⁶ cells/ml, 93.3 %) were compatible to those obtained with Ficoll (1.34 × 10⁶ cells/ml, 97.2 %). No differences in the mean purity, recovery, and viability of CD19+ (B cells), CD8+ (cytotoxic T cells), CD4+ (helper T cell) and CD14+ (monocytes) positively selected from CPT- or Ficoll-isolated PBMC were found. Similar quantities of high quality RNA and DNA were extracted from PBMC and immune cells obtained by both methods. Finally, the PBMC isolation methods tested did not impact subsequent recovery and purity of individual immune cell subsets and, importantly, their gene expression profiles.

Conclusions

Our findings demonstrate that the CPT and Ficoll PBMC isolation protocols do not differ in their ability to purify high quality immune cell subpopulations. Since there was no difference in the gene expression profiles between immune cells obtained by these two methods, the Ficoll isolation can be substituted by the CPT protocol without conceding phenotypic changes of immune cells and compromising the gene expression studies. Given that the CPT protocol is less elaborate, minimizes cells’ handling and processing time, this method offers a significant operating advantage, especially in large-scale clinical studies aiming at dissecting gene expression in PBMC and PBMC-derived immune cell subpopulations.

Electronic supplementary material

The online version of this article (doi:10.1186/s12865-015-0113-0) contains supplementary material, which is available to authorized users.

A microfluidic chip for direct and rapid trapping of white blood cells from whole blood

Blood analysis plays a major role in medical and science applications and white blood cells (WBCs) are an important target of analysis. We proposed an integrated microfluidic chip for direct and rapid trapping WBCs from whole blood. The microfluidic chip consists of two basic functional units: a winding channel to mix and arrays of two-layer trapping structures to trap WBCs. Red blood cells (RBCs) were eliminated through moving the winding channel and then WBCs were trapped by the arrays of trapping structures. We fabricated the PDMS (polydimethylsiloxane) chip using soft lithography and determined the critical flow velocities of tartrazine and brilliant blue water mixing and whole blood and red blood cell lysis buffer mixing in the winding channel. They are 0.25 μl/min and 0.05 μl/min, respectively. The critical flow velocity of the whole blood and red blood cell lysis buffer is lower due to larger volume of the RBCs and higher kinematic viscosity of the whole blood. The time taken for complete lysis of whole blood was about 85 s under the flow velocity 0.05 μl/min. The RBCs were lysed completely by mixing and the WBCs were trapped by the trapping structures. The chip trapped about 2.0 × 10(3) from 3.3 × 10(3) WBCs.

Microfluidic inertia enhanced phase partitioning for enriching nucleated cell populations in blood

Nucleated cells in blood like white blood cells (WBCs) and other rare cells including peripheral blood stem cells (PBSCs) and circulating tumor cells (CTCs) possess significant value for patient monitoring and clinical diagnosis. Enrichment of nucleated cells from contaminating red blood cells (RBCs) using label-free techniques without the use of antibodies or centrifugation is highly desirable to ensure minimal cell loss and activation. To accomplish this, we demonstrate proof-of-concept of a new microfluidic technique that combines aqueous phase partitioning with inertial focusing to accomplish enrichment of nucleated cells in blood. This technique exploits selective affinity of RBCs to the dextran phase (DEX) to accomplish initial separation which is amplified by inertial forces that develop in high-aspect-ratio channels. In our experiments, we spiked RBC samples with representative nucleated cells, MOLT-3 cells (human, peripheral blood, T lymphoblast cell line) and MCF-7 cells (human breast cancer cell line) in a ratio of 500 : 1 (RBCs : nucleated cells) and accomplished depletion of ~96% of RBCs while retaining ~98% of nucleated cells. Higher purity can be accomplished by subjecting the enriched nucleated cell mixture to a second pass via the same process. The second pass further enhances RBC depletion (>99% of initial concentration) whereas nucleated cells were recovered without any further loss. This technique therefore has the potential to be utilized either alone or as a sample preparation tool in the clinical and research setting for various clinical and research applications.

Mitochondrial dysfunction in Trypanosoma cruzi: the role of Serratia marcescens prodigiosin in the alternative treatment of Chagas disease

BACKGROUND

Chagas disease is a health threat for many people, mostly those living in Latin America. One of the most important problems in treatment is the limitation of existing drugs. Prodigiosin, produced by Serratia marcescens (Rhodnius prolixus endosymbiont), belongs to the red-pigmented bacterial prodiginine family, which displays numerous biological activities, including antibacterial, antifungal, antiprotozoal, antimalarial, immunosuppressive, and anticancer properties. Here we describe its effects on Trypanosoma cruzi mitochondria belonging to Tc I and Tc II.

RESULTS

Parasites exposed to prodigiosin altered the mitochondrial function and oxidative phosphorylation could not have a normal course, probably by inhibition of complex III. Prodigiosin did not produce cytotoxic effects in lymphocytes and Vero cells and has better effects than benznidazole. Our data suggest that the action of prodigiosin on the parasites is mediated by mitochondrial structural and functional disruptions that could lead the parasites to an apoptotic-like cell death process.

CONCLUSIONS

Here, we propose a potentially useful trypanocidal agent derived from knowledge of an important aspect of the natural life cycle of the parasite: the vector-parasite interaction. Our results indicate that prodigiosin could be a good candidate for the treatment of Chagas disease.

Phenotypic analysis using very small volumes of blood

Analysis of cell-surface phenotype of peripheral blood leukocytes is one of the most common applications of flow cytometry. In mouse research, the small size of the animal limits the amount of blood available. Standard staining methods using lysis of erythrocytes or gradient separation followed by repeated washing involve unavoidable losses of cells that generally limit analysis of blood to terminal methods. Time-course studies, therefore, require sacrifice of groups of mice at each time point. Thus, a method is needed that can be used with much smaller volumes of blood. This will allow serial sampling of the same animal over time, decreasing experimental variability and reducing animal use. The method described here is a no-lyse, no-wash method that uses triggering on a fluorescence parameter. The method allows routine analysis of the phenotype of peripheral blood leukocytes using whole-blood volumes of 20 µl per tube. The data are comparable with values from traditional methods requiring much higher volumes of blood. Due to interference by erythrocytes, light-scatter parameters are not usable with this method. This method has been used for time-course studies of peripheral blood populations in mice lasting as long as four weeks.

Identification of internal control genes for quantitative expression analysis by real-time PCR in bovine peripheral lymphocytes

Gene expression studies in blood cells, particularly lymphocytes, are useful for monitoring potential exposure to toxicants or environmental pollutants in humans and livestock species. Quantitative PCR is the method of choice for obtaining accurate quantification of mRNA transcripts although variations in the amount of starting material, enzymatic efficiency, and the presence of inhibitors can lead to evaluation errors. As a result, normalization of data is of crucial importance. The most common approach is the use of endogenous reference genes as an internal control, whose expression should ideally not vary among individuals and under different experimental conditions. The accurate selection of reference genes is therefore an important step in interpreting quantitative PCR studies. Since no systematic investigation in bovine lymphocytes has been performed, the aim of the present study was to assess the expression stability of seven candidate reference genes in circulating lymphocytes collected from 15 dairy cows. Following the characterization by flow cytometric analysis of the cell populations obtained from blood through a density gradient procedure, three popular softwares were used to evaluate the gene expression data. The results showed that two genes are sufficient for normalization of quantitative PCR studies in cattle lymphocytes and that YWAHZ, S24 and PPIA are the most stable genes.

Loss of negative feedback control of nuclear factor-kappaB2 activity in lymphocytes leads to fatal lung inflammation

Proteolytic processing of the nuclear factor (NF)-kappaB2 precursor protein p100 generates the active NF-kappaB2 subunit p52, which in turn transcriptionally up-regulates p100 expression. p100 also functions as an IkappaB molecule capable of repressing p52 activity. The biological significance of this negative feedback control loop has yet to be demonstrated in vivo. Here we show that mice deficient in p100 but with constitutive expression of p52 in lymphocytes developed fatal lung inflammation characterized by diffuse alveolar damage with marked peribronchial fibrosis. In contrast, their littermates with only p100 deficiency or constitutive expression of p52 in lymphocytes developed mild lung inflammation with perivascular lymphocyte infiltration and had a normal life span. The fatal lung inflammation is associated with high-level induction of interferon-gamma and its inducible inflammatory chemokines, suggesting the involvement of a T-helper-1 immune response. These findings demonstrate the physiological relevance of the NF-kappaB2 p100 precursor protein in limiting the potentially detrimental effects of constitutive NF-kappaB2 signaling in lymphocytes.

Neutrophil migration assay from a drop of blood

Neutrophil directional migration in response to chemical gradients, also known as chemotaxis, is one of the key phenomena in the immune responses against bacterial infection. To better study neutrophils chemotaxis, several in vitro assays have been developed that replicate chemotactic gradients around neutrophils isolated from whole blood. One drawback for most of these assays is the lengthy processing of blood required for neutrophils isolation, which can alter the responsiveness of neutrophils compared to the in vivo conditions. To address this limitation, we have designed a microfluidic chip for chemotaxis studies which can use neutrophils isolated on the chip, directly from whole blood. We have tested three different cell adhesion molecules as substrates for neutrophil isolation (P-selectin, E-selectin and fibronectin) and found average capture efficiencies of 20-40 neutrophils/mm2 at optimized concentrations. Subsequent analysis of neutrophil migration in chemoattractant gradients of N-formyl-methyl-leucyl-phenylalanine (fMLP) or Interleukin-8 (IL-8) shows higher average velocities over E-selectin as compared to the P-selectin. Our microfluidic assay uses just a drop of whole blood (<10 microL) for neutrophil isolation and provides a robust platform to perform chemotaxis assays in the competing environment of different chemokines.

Winter day lengths enhance T lymphocyte phenotypes, inhibit cytokine responses, and attenuate behavioral symptoms of infection in laboratory rats

Annual variations in day length (photoperiod) trigger changes in the immune and reproductive system of seasonally-breeding animals. The purpose of this study was to determine whether photoperiodic changes in immunity depend on concurrent photoperiodic responses in the reproductive system, or whether immunological responses to photoperiod occur independent of reproductive responses. Here we report photoperiodic changes in enumerative, functional, and behavioral aspects of the immune system, and in immunomodulatory glucocorticoid secretion, in reproductively non-photoperiodic Wistar rats. T-cell numbers (CD3+, CD8+, CD8+CD25+, CD4+CD25+) were higher in the blood of rats housed in short as opposed to long-day lengths for 10 weeks. Following a simulated bacterial infection (Escherichia coli LPS; 125 microg/kg) the severity of several acute-phase sickness behaviors (anorexia, cachexia, neophobia, and social withdrawal) were attenuated in short days. LPS-stimulated IL-1beta and IL-6 production were comparable between photoperiods, but plasma TNFalpha was higher in long-day relative to short-day rats. In addition, corticosterone concentrations were higher in short-day relative to long-day rats. The data are consistent with the hypothesis that photoperiodic regulation of the immune system can occur entirely independently of photoperiodic regulation of the reproductive system. In the absence of concurrent reproductive responses, short days increase the numbers of leukocytes capable of immunosurveillance and inhibition of inflammatory responses, increase proinflammatory cytokine production, increase immunomodulatory glucocorticoid secretion, and ultimately attenuate behavioral responses to infection. Seasonal changes in the host immune system, endocrine system, and behavior may contribute to the seasonal variability in disease outcomes, even in reproductively non-photoperiodic mammals.

Continuous flow microfluidic device for rapid erythrocyte lysis

Leukocyte isolation from whole blood to study inflammation requires the removal of contaminating erythrocytes. Leukocytes, however, are sensitive to prolonged exposure to hyper/hypoosmotic solutions, temperature changes, mechanical manipulation, and gradient centrifugation. Even though care is taken to minimize leukocyte activation and cell loss during erythrocyte lysis, it is often not possible to completely avoid it. Most procedures for removal of contaminating erythrocytes from leukocyte preparations are designed for bulk processing of blood, where the sample is manipulated for longer periods of time than necessary at the single-cell level. Ammonium chloride-mediated lysis is the most commonly used method to obtain enriched leukocyte populations but has been shown to cause some activation and selective loss of certain cell types. The leukocyte yield and subsequent activation status of residual leukocytes after NH(4)Cl-mediated lysis have been shown to depend on the time of exposure to the lysis buffer. We have developed a microfluidic lysis device that deals with erythrocyte removal at nearly the single-cell level. We can achieve complete lysis of erythrocytes and approximately 100% recovery of leukocytes where the cells are exposed to an isotonic lysis buffer for less than 40 s, after which the leukocytes are immediately returned to physiological conditions. Theoretically, this process can be made massively parallel to process several milliliterss of whole blood to obtain a pure leukocyte population in less than 15 min.

Various adhesion molecules impair microvascular leukocyte kinetics in ventilator-induced lung injury

Although the endothelial expression of various adhesion molecules substantially differs between pulmonary microvessels, their importance for neutrophil and lymphocyte sequestration in ventilator-induced lung injury (VILI) has not been systematically analyzed. We investigated the kinetics of polymorphonuclear cells (PMN) and mononuclear cells (MN) in the acinar microcirculation of the isolated rat lung with VILI by real-time confocal laser fluorescence microscopy, with or without inhibition of ICAM-1, VCAM-1, or P-selectin by monoclonal antibodies (MAb). Adhesion molecules in each microvessel were estimated by intravital fluorescence microscopy or immunohistochemical staining. In high tidal volume-ventilated lungs, 1) ICAM-1, VCAM-1, and P-selectin were differently upregulated in venules, arterioles, and capillaries; 2) venular PMN rolling was improved by inhibition of ICAM-1, VCAM-1, or P-selectin, whereas arteriolar PMN rolling was improved by ICAM-1 or VCAM-1 inhibition; 3) capillary PMN entrapment was ameliorated only by anti-ICAM-1 MAb; and 4) MN rolling in venules and arterioles and MN entrapment in capillaries were improved by ICAM-1 and VCAM-1 inhibition. In conclusion, the contribution of endothelial adhesion molecules to abnormal leukocyte behavior in VILI-injured microcirculation is microvessel and leukocyte specific. ICAM-1- and VCAM-1-dependent, but P-selectin-independent, arteriolar PMN rolling, which is expected to reflect the initial stage of tissue injury, should be taken as a phenomenon unique to ventilator-associated lung injury.

Age-related alterations to immune parameters in Labrador retriever dogs

In order to assess age-related changes in the immune status of Labrador retriever dogs, leukocyte phenotypes, lymphocyte proliferative capacity, and serum antibody levels were measured in four cohorts of dogs, ranging from 2 to 10 years of age. Absolute numbers of white blood cells, lymphocytes, monocytes, granulocytes, and CD3+, CD4+, CD8+ and CD21+ lymphocytes significantly decreased with increasing age. Relative percentages of lymphocytes and CD4 cells were significantly decreased, and relative percentages of granulocytes and CD8 cells significantly increased, with age. The CD4:CD8 ratio showed a significant age-related decrease. Proliferative responses of T-cells to mitogens in whole-blood cultures either increased (Concanavalin A) or remained the same (phytohemagglutinin) with age when data was normalised to allow for differences in responding cell number. Similarly, normalised data of proliferative response to anti-CD3 stimulation together with phorbol 12-myristate 13-acetate showed an age-related increase. Serum levels of total IgA significantly increased with age whereas total IgG levels remained unchanged. These observations illustrate a significant change to a number of immune parameters with age. However, further work is required to determine whether the differences reported here are sufficient to cause overt or functional immune senescence in Labrador retriever dogs.

Circadian rhythms in surface molecules of rat blood lymphocytes

The present article examines whether the expression of certain surface molecules that trigger immune responses shows a circadian rhythm. We also analyzed the rhythms in the number and percentage of lymphocyte subpopulations, in the leukocyte differential counts, and in the total red and white blood cell counts. Blood samples obtained from rats at 2-h intervals for 24 h were stained with several mouse monoclonal antibodies directed against lymphocyte surface molecules and processed by flow cytometry. The number of B, total T, Tgammadelta, Th, and Ts/c cells followed a 24-h rhythm with a peak in the first half of the resting period. The expression of CD45, CD5, CD3, and CD4 followed a circadian rhythm. Their acrophases suggested temporal association between CD45 and CD5 at the end of the active phase and between CD4 and CD3 at the beginning of this phase. This temporal organization could have an important role for immune cell function.

A small-volume technique for simultaneous immunophenotyping and apoptosis detection in rat whole blood by four-color flow cytometry

BACKGROUND

Cell permeabilization for the detection of intracellular molecules by flow cytometry is usually incompatible with whole blood. This article describes a new technique for the simultaneous detection of surface antigens and DNA content in rat whole blood.

METHODS

In 20 microl of rat whole blood, DNA staining is obtained by permeabilization of cells using a standard red blood cell lysing reagent (Erythrolyse). Immunophenotyping and apoptosis detection by flow cytometry are achieved by using a combination of three surface markers (CD3, CD4, and CD8alpha) and a DNA binding dye (TO-PRO-3).

RESULTS

After a 24-h incubation of whole blood with 1 microM dexamethasone, apoptotic lymphocytes were clearly distinguishable from normal lymphocytes by their reduced size and DNA content. The dexamethasone-induced percentage of apoptotic cells was 58.9 +/- 4.6 for CD4+ and 77.4 +/- 2.9 for CD8+ T cells, compared with 12.6 +/- 2.7 for CD4+ and 17.2 +/- 3.5 for CD8+ T cells in the absence of dexamethasone (data from 10 animals with duplicate samples).

CONCLUSIONS

We have developed a new technique to permeabilize nucleated cells in microsamples of rat whole blood. The methodology allows simultaneous immunophenotyping and apoptosis detection in rat whole blood.

Roles of ICAM-1 for abnormal leukocyte recruitment in the microcirculation of bleomycin-induced fibrotic lung injury

To assess the importance of endothelial intercellular adhesion molecule-1 (ICAM-1) in microvascular leukocyte kinetics in diseased lungs, we investigated the transitional changes in ICAM-1 expression, vascular diameter, and leukocyte behavior in rat pulmonary microcirculation during the development of acute lung injury (ALI) and chronic fibrosis (FIB) evoked by bleomycin (BLM). Observations were made in the isolated perfused lung with a real-time confocal laser luminescence microscope. Microvascular cell kinetics were evaluated by measuring the behavior of fluorescence- labeled leukocytes and erythrocytes in the presence or absence of anti-ICAM-1 monoclonal antibody (1A29). Arteriolar ICAM-1 showed little change at any time after BLM treatment. Venular ICAM-1 was first enhanced at the initial phase of ALI followed by the second upregulation at the early phase of FIB. Capillary ICAM-1 showed a sustained increase at both ALI and FIB. Arteriolar and venular diameters were not altered but capillary diameter decreased during ALI and early FIB stages. Although firm adherence of leukocytes to arteriolar and venular walls was not observed, rolling leukocytes were increased in venules both at the initial phase of ALI and at the early phase of FIB. The leukocyte rolling in venules correlated well with transitional changes in ICAM-1 and was inhibited by 1A29. Sustained entrapment of leukocytes in capillaries was attributed to changes in vascular diameter as well as augmented ICAM-1. In conclusion, ICAM-1 plays an important role in microvascular leukocyte recruitment in both ALI and FIB in the BLM-injured lung.

Chronic marginal vitamin A status reduces natural killer cell number and function in aging Lewis rats

Natural killer (NK) cells function in the regulation of immune responses and in the surveillance of malignant or other abnormal cells. Little is known of the effects of chronic marginal vitamin A (VA) status or VA supplementation, or their interaction with age, on NK cell number and cytolytic activity. We have conducted a two-factor (diet, age) study in which male Lewis rats were fed AIN-93M diet, modified to contain either 0.3 (designated marginal), 4.0 (control) or 50 (supplemented) mg retinol equivalents (RE)/kg diet, from the time of weaning until the ages of 2.5 mo (young), 8-10 mo (middle-aged) or 18-20 mo (old). Natural killer cells were identified and quantified in peripheral blood mononuclear cells (PBMC) and spleen with the use of flow cytometry, and NK cell cytotoxicity was assayed. The number and percentage of PBMC NK cells increased with age (P < 0.0001 by two-way ANOVA). For all age groups, values were lowest in rats with marginal VA status (P < 0.0001 vs. controls). NK cell lytic activity also declined with age (P = 0. 0003). As a result, NK cell lytic efficiency (lytic activity per NK cell) decreased markedly with age (P < 0.0001). Regardless of the donor's age or VA status, PBMC NK cell cytotoxicity doubled (100 +/- 25% increase) after exposure to interferon-alpha (5 x 10(5) U/L for 1 h before assay), indicating that IFN-stimulated lytic activity was related directly to basal NK cell activity. If the relationships observed in this animal model can be applied to humans, these data suggest that elderly people consuming diets chronically low in VA may be at increased risk for infectious or neoplastic diseases.

Evaluation of a novel mononuclear cell isolation procedure for serological HLA typing

Despite recent advances in DNA-based genotyping, the microcytotoxicity test is still broadly used for the determination of human leukocyte class I antigens in patients as well as organ donors and also for the detection of HLA antibodies. Excellent purity and viability of peripheral blood mononuclear cells (PBMC) are essential for reliable HLA typing results. Background staining and cell loss can contribute to impaired typing results or even cause misinterpretations. A novel isolation procedure using cell preparation tubes (CPT) with prefilled Ficoll was compared with the standard Ficoll gradient. We determined the recovery, purity, and viability of the PBMC after several periods of storage. Finally, the isolated cells were used for HLA class I typing, and background reactivities were scored. By using the CPT method, the recovery of PBMC was significantly higher than recovery with the standard technique (P Collapse

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MESH Headings

• Cell Separation/methods
• Cell Survival
• Centrifugation, Density Gradient/methods
• Cytotoxicity, Immunologic
• Evaluation Studies as Topic
• Flow Cytometry
• Histocompatibility Testing
• Humans
• Leukocytes, Mononuclear/classification
• Leukocytes, Mononuclear/cytology
• Leukocytes, Mononuclear/physiology
• Specimen Handling
• Time Factors

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Affiliation(s)

P Schlenke Institute of Immunology and Transfusion Medicine, University of Luebeck School of Medicine, D23538 Luebeck, Germany.
H Klüter
M Müller-Steinhardt
H J Hammers
K Borchert
G Bein

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Kinetics of W3/25 anti-rat CD4 monoclonal antibody. Studies on optimal doses and time-related effects

Although anti-CD4 monoclonal antibodies (MoAb) have been proven successful in preventing or treating adjuvant arthritis, little is known about the duration of the effects of these MoAb and their pharmacokinetics. In this work, we report the effects of a mouse anti-rat CD4 MoAb, named W3/25, on peripheral blood lymphocytes from female Wistar rats. Animals received a single dose of W3/25, from 1 to 3 mg, and blood was sampled at different time points from 0 h to 15 days after MoAb administration. After erythrocyte lysis, samples were stained by indirect immunofluorescence and analyzed by flow cytometry. Pharmacokinetic data were studied by assessing plasma levels of mouse IgG1 by ELISA-sandwich. W3/25 produced the down-regulation of surface CD4 molecule as early as 20 min after its administration at doses of 2 and 3 mg. The same effect was seen 30 min after a dose of 1 mg. The recovery of lymphocytes with normal expression of CD4 also depended of the dose administered. Thus, CD4+ lymphocytes were recovered at 48, 72 and 96 h in rats treated with 1, 2 or 3 mg of W3/25, respectively. Plasma levels of free antibody were detectable from 20 min to 72 h, 60 min to 48 h and 60 min to 24 h after administration of 3, 2 and 1 mg, respectively, of W3/25. The mouse IgG1 MoAb used in this study followed a two-compartment model and its behavior was linear.

Immunophenotyping analysis of peripheral blood, splenic, and thymic lymphocytes in male and female rats

A flow cytometry method was used to characterize lymphoid tissue-associated lymphocyte subsets in the Sprague-Dawley rat. Mononuclear leukocytes from peripheral blood, spleen, and thymus of male and female rats were labeled with a panel of fluorescently tagged monoclonal and polyclonal antibodies directed against specific cell-surface proteins. The differential expression of these marker proteins was used to phenotypically distinguish one subpopulation of lymphocytes from another when analyzed via flow cytometry. This method was used to determine the relative percentages and absolute number of total B cells (CD45RA+; sIgM+), total T cells (CD3+; pan-T+), helper T cells (CD3 + CD4+), cytotoxic/ suppressor T cells (CD3 + CD8+), and the CD4:CD8 ratio in each of these lymphoid tissues. Additionally, all subsets of differentiating T cells in the thymus (i.e., CD4 + CD8-, CD4-CD8+, CD4 + CD8+, and CD4-CD8-cells) were distinguished using dual parameter analyses. Results of this study demonstrate that 1) the selected panel of antibodies used in this study can identify all lymphocyte subsets present in blood, spleen, and thymus of the rat and 2) male and female Sprague-Dawley rats show slight, but not statistically significant, differences in the proportions of some lymphocyte subsets present in select lymphoid tissues. This flow cytometry method can be used to accurately assess the potential immunotoxic or immunomodulatory effect of xenobiotic agents as characterized by changes in the phenotypic expression patterns or alterations in the quantity of lymphocyte subpopulations in the rat.