Separation of T and B lymphocytes from human peripheral blood mononuclear cells using density perturbation methods

Interaction of Cholera Toxin B-subunit with Human T-lymphocytes

In this work, ¹²⁵I-labeled cholera toxin B-subunit (CT-B) (specific activity 98 Ci/mmol) was prepared, and its high-affinity binding to human blood T-lymphocytes (K_d = 3.3 nM) was determined. The binding of the ¹²⁵I-labeled CT-B was inhibited by unlabeled interferon-α₂ (IFN-α₂), thymosin-α₁ (TM-α₁), and by the synthetic peptide LKEKK, which corresponds to sequences 16-20 of human TM-α₁ and 131-135 of IFN-α₂ (K_i 0.8, 1.2, and 1.6 nM, respectively), but was not inhibited by the unlabeled synthetic peptide KKEKL with inverted sequence (K_i > 1 µM). In the concentration range of 10-1000 nM, both CT-B and peptide LKEKK dose-dependently increased the activity of soluble guanylate cyclase (sGC) but did not affect the activity of membrane-bound guanylate cyclase. The KKEKL peptide tested in parallel did not affect sGC activity. Thus, the CT-B and peptide LKEKK binding to a common receptor on the surface of T-lymphocytes leads to an increase in sGC activity.

Interaction of cholera toxin B subunit with T and B lymphocytes

We have prepared ¹²⁵I-labeled cholera toxin B subunit (¹²⁵I-labeled CT-B, a specific activity of 98Ci/mmol) and found that its binding to T and B lymphocytes from the blood of healthy donors was high-affinity (K_d 2.8 and 3.0nM, respectively). The binding of labeled protein was completely inhibited by unlabeled thymosin-α₁ (TM-α₁), interferon-α₂ (IFN-α₂), and the synthetic peptide LKEKK that corresponds to residues 16-20 in TM-α₁ and 131-135 in IFN-α₂, but was not inhibited by the synthetic peptide KKEKL with inverted amino acid sequence (K_i>10μM). Thus, TM-α₁, IFN-α₂, and the peptide: LKEKK bind with high affinity and specificity to CT-B receptor on donor blood T and B lymphocytes. It was found that CT-B and the peptide: LKEKK at concentrations of 10-1000nM increased in a dose-dependent manner the soluble guanylate cyclase activity in T and B lymphocytes.

Binding of Synthetic LKEKK Peptide to Human T-Lymphocytes

The synthetic peptide LKEKK corresponding to sequence 16-20 of human thymosin-α1 and 131-135 of human interferon-α2 was labeled with tritium to specific activity 28 Ci/mol. The [3H]LKEKK bound with high affinity (Kd = 3.7 ± 0.3 nM) to donor blood T-lymphocytes. Treatment of cells with trypsin or proteinase K did not abolish [3H]LKEKK binding, suggesting the non-protein nature of the peptide receptor. The binding was inhibited by thymosin-α1, interferon-α2, and cholera toxin B subunit (Ki = 2.0 ± 0.3, 2.2 ± 0.2, and 3.6 ± 0.3 nM, respectively). Using [3H]LKEKK, we demonstrated the existence of a non-protein receptor common for thymosin-α1, interferon-α2, and cholera toxin B-subunit on donor blood T-lymphocytes.

Influence of the programmed cell death of lymphocytes on the immunity of patients with atopic bronchial asthma

BACKGROUND

Fairly recent data highlight the role of programmed cell death and autoimmunity, as potentially important factors in the pathogenesis of chronic obstructive airway diseases. The purpose of our research was to determine the influence of apoptotic factors on the immunity of patients with atopic bronchial asthma according to the degree of severity.

METHOD

The study was performed on the peripheral blood of patients with atopic bronchial asthma with different severity. The Immunological aspects were determined with ELISA, the fluorimetric method and the method of precipitation with polyethylene glycol. And the quantification of the parameters of the programmed cell death was performed by the method of flow cytometry and electron microscopy method.

RESULTS

The data obtained from morphological and biochemical parameters show the deregulation of Programmed Death of lymphocytes of patients with atopic bronchial asthma but individual for each group of patients. This dysfunction might induce the secretion of autoantibodies against DNA. This could explain the accumulation of circulating immune complex with average size considered as the most pathogenic in patients with bronchial asthma especially in the patients of serious severity. It should be noted that Patients with bronchial asthma of mild and severe severity had different way and did not have the same degree of deficiency of the immune system.

CONCLUSION

These data suggested that apoptotic factor of lymphocytes may play an important role in controlling immunity of patients with atopic bronchial asthma.

Chromatography of living cells using supermacroporous hydrogels, cryogels

The preparative cell separation is an intrinsic requirement of various diagnostic, biotechnological and biomedical applications. Affinity chromatography is a promising technique for cell separation and is based on the interaction between a cell surface receptor and an immobilised ligand. Most of the currently available matrices have pore size smaller than the size of the cells and are not suitable for cell chromatography due to column clogging. Another problem encountered in chromatographic separation of cells is a difficulty to elute bound cells from affinity surfaces. Application of novel adsorbents, supermacroporous monolithic cryogels, allows overcoming these problems. Cryogels are characterised by highly interconnected large (10-100 microm) pores, sponge-like morphology and high elasticity. They are easily derivatised with any ligand of choice. Convective migration can be used to transport the cells through the matrix. Target cells bind to affinity ligands, while other cells pass through the cryogel column non-retained and are removed during a washing step. Because of the spongy and elastic nature of the cryogel matrices, the cells are efficiently desorbed by mechanical compression of cryogels, which provides high cell viability and yields. The release of affinity bound cells by mechanical compression of a cryogel monolithic adsorbent is a unique and efficient way of cell detachment. This detachment strategy and the continuous macroporous structure make cryogels very attractive for application in cell separation chromatography.

Enrichment using antibody-coated microfluidic chambers in shear flow: model mixtures of human lymphocytes

Isolation of phenotypically-pure cell subpopulations from heterogeneous cell mixtures such as blood is a difficult yet fundamentally important task. Current techniques such as fluorescent activated cell sorting (FACS) and magnetic-activated cell sorting (MACS) require pre-incubation with antibodies which lead to processing times of at least 15-60 min. In this study, we explored the use of antibody-coated microfluidic chambers to negative deplete undesired cell types, thus obtaining an enriched cell subpopulation at the outlet. We used human lymphocyte cell lines, MOLT-3 and Raji, as a model system to examine the dynamic cell binding behavior on antibody coated surfaces under shear flow. Shear stress ranging between 0.75 and 1.0 dyn/cm2 was found to provide most efficient separation. Cell adhesion was shown to follow pseudo-first order kinetics, and an anti-CD19 coated (Raji-depletion) device with approximately 2.6 min residence time was demonstrated to produce 100% pure MOLT-3 cells from 50-50 MOLT-3/Raji mixture. We have developed a mathematical model of the separation device based on the experimentally determined kinetic parameters that can be extended to design future separation modules for other cell mixtures. We conclude that we can design microfluidic devices that exploits the kinetics of dynamic cell adhesion to antibody coated surfaces to provide enriched cell subpopulations within minutes of total processing time.

Affinity fractionation of lymphocytes using a monolithic cryogel

A new type of continuous, supermacroporous, monolithic, cryogel affinity adsorbent was developed, allowing specific fractionation and separation of human peripheral blood lymphocytes in a chromatographic format. The affinity adsorbent was used to design a novel cell separation strategy, which was based on the interaction of protein A from Staphylococcus aureus with cells bearing IgG antibodies on the surface. After treating lymphocytes with goat anti-human IgG(H+L), the IgG-positive B-lymphocytes were efficiently separated from T-lymphocytes. Protein A covalently coupled to epoxy activated dimethylacrylamide (DMAA) cryogel matrix specifically bound IgG-bearing B-lymphocytes through the Fc region, while non-bound T-lymphocytes passed through the column. More than 90% of the B-lymphocytes were retained in the column while the cells in the breakthrough fraction were enriched in T-lymphocytes (81%). The viability of the T-lymphocytes isolated was greater than 90%. The bound lymphocytes released by human or dog IgG recovered 60-70% of the B-cells without significantly impairing the cell viability. The technique can be applied in general to cell separation systems where IgG antibodies against specific cell surface markers are available.

An investigation into the suitability of silica beads for cell separations based on density perturbation

This study has investigated possible alternative types of beads for fractionating cells on the basis of density perturbation. It is well known that uniform magnetic beads can be extremely important tools for separating cells by both magnetic separation techniques and density perturbation. However, because of the inherent expense associated with the use of magnetic beads, it was decided to study the possible use of inexpensive silica beads for density perturbation in terms of their attachment and modification of density of cells and to compare them with uniform Dynabeads. Silica beads were analyzed to determine their size and effect on the density of cells. Differentiated HL60 cells were used as a model system. As differentiation occurs, different levels of antigens are expressed on the cell surface and this results in different numbers of beads binding to cells. DMSO-differentiated HL60 cells were mixed with anti-CD11b-coated beads at a ratio of 20:1 (beads/cell), and gentle mixing was carried out at 20 degrees C on the end-over-end mixer. The binding of antibody-coated silica beads and Dynabeads to partially differentiated HL60 cells were compared. The conclusions reached on the basis of these experiments are that antibody-coated silica beads (Ab-coated silica) can be used as alternative beads for some cell fractionations. However, compared with Dynabeads, there are more beads that are only transiently associated with cells, possibly indicating that higher levels of detachment of beads from cells occur when silica beads are used. In addition, silica beads are usually heterogeneous in size and this would make it difficult to use these beads for the isolation of purified subpopulations of differentiated cells.

Fractionation of differentiating cells using density perturbation

This paper describes the development of a new method for the fractionation of purified subpopulations of partially differentiated cells on continuous isopycnic gradients, using a density perturbation method based on the ability of cells to bind dense antibody-coated beads. Until now none of the available fractionation techniques, such as magnetic cell fractionation has been efficient for separating subpopulations of partially differentiated cells. The fractionation experiments described in this report used promyelocytic HL-60 and DMSO-induced granulocytic HL-60 cells as a model system. Populations of cells, modified by the binding of dense beads were fractionated on isotonic, isopycnic Optiprep gradients by centrifugation at 220xg for 90 min at 20 degrees C. Examination of the different gradient fractions showed that, as cells bind increasing numbers of beads, they are found in the denser regions of the isopycnic gradients. Indirect immunofluorescence was combined with flow cytometric techniques to characterise the fractionation of partially differentiated cells. Flow cytometric results confirmed that as antigenic determinants appear on the surface at higher levels of expression, the number of beads binding to each cell increased. Furthermore, after fractionation, when the bead-bound and non-bead-bound cells were cultured in the presence of DMSO, those cells that had bound more beads targeted to differentiated cells were found to achieve terminal differentiation faster than those cells that had not been associated with any beads.