Efficient separation of human T lymphocytes from venous blood using PVP-coated colloidal silica particles (percoll)

Cell separation using cryogel-based affinity chromatography

In cell affinity chromatography, type-specific cell separation is based on the interaction between cell-surface receptors and an immobilized ligand on a stationary matrix. This protocol describes the preparation of monolithic polyacrylamide and polydimethylacrylamide cryogel affinity matrices that can be used as a generic type-specific cell separation approach. The supermacroporous monolithic cryogel has highly interconnected large pores (up to 100 μm) for convective migration of large particles such as mammalian cells. In this protocol, they are functionalized to immobilize a protein A ligand by a two-step derivatization of epoxy-containing cryogel monolith (reaction with ethylenediamine and glutaraldehyde). Target cells were labeled with specific antibodies and then they were captured in the cryogel through affinity with protein A. These specifically captured cells were recovered in high yields while retaining their viability by mechanical squeezing of the spongy and elastic cryogel matrices. The suggested cell separation protocol takes < 30 min for complete separation on a preprepared protein A-immobilized cryogel column.

Mammalian plasma membrane proteomics

Plasma membrane proteins serve essential functions for cells, interacting with both cellular and extracellular components, structures and signaling molecules. Additionally, plasma membrane proteins comprise more than two-thirds of the known protein targets for existing drugs. Consequently, defining membrane proteomes is crucial to understanding the role of plasma membranes in fundamental biological processes and for finding new targets for action in drug development. MS-based identification methods combined with chromatographic and traditional cell-biology techniques are powerful tools for proteomic mapping of proteins from organelles. However, the separation and identification of plasma membrane proteins remains a challenge for proteomic technology because of their hydrophobicity and microheterogeneity. Creative approaches to solve these problems and potential pitfalls will be discussed. Finally, a representative overview of the impressive achievements in this field will also be given.

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.

Analysis of high and low responses to Staphylococcus aureus and interleukin 2 in human B lymphocytes

Fixed protein A-bearing staphylococci (SAC) stimulate human B cells via surface Ig, whereas IL-2 has been reported to provide a sufficient second signal for proliferation and differentiation. Using an ELISPOT assay to count cells secreting IgM, IgA, and IgG and flow cytometry with acridine orange to assess cell cycle progress, we have found that the purified B lymphocytes of a substantial minority (5/13) of healthy volunteers with normal serum Ig levels failed to differentiate to Ig secreting cells (ISC) in response to SAC + IL-2 (IgM, IgA, or IgG secreting cells, < 5% of input B cells). High-responders generally formed 10-35% ISC. The proportions of B cells expressing IgG, IgA, IgM, or IgD were not different in the two groups. By average linkage cluster analysis, SAC/IL-2 high- and low-responders were shown to fall into two separate populations with respect to ISC. High- and low-responders tended to remain in the same group with repeated testing over several months, although some convergence was seen. The low-responders also showed significantly less advancement to late G1 and S phase than the high-responders, in the presence of SAC +/- IL-2. Induction of IL-2 receptors on B cells by SAC + IL-2 was much greater in high-responders than in low-responders, as shown by flow cytometry with phycoerythrin-conjugated IL-2. However, SAC + IL-2 induced transferrin receptors normally in low-responders, showing that some early activation steps occur in these cells. Low-responder B cells often improved their responses in the presence of macrophages and T cell supernatants. Finally, bypassing the surface Ig pathway using anti-CD3-activated T cells to stimulate B cells produced normal differentiation in low-responder B cells. Thus a subset of clinically normal individuals possesses B cells which fail to express IL-2 receptors, proliferate, and differentiate normally in vitro in response to SAC + IL-2 yet can respond well to alternative activation pathways via T cells, monocytes, and their products.

Cell-mediated cytotoxicity in hepatitis A virus infection

We studied cell-mediated cytotoxicity to hepatitis A virus-infected cells in seven patients with acute type A hepatitis and two controls. Skin fibroblast cultures obtained from the skin biopsies of seven patients after acute hepatitis A virus infection and from two persons without history of current or past hepatitis A virus infection were inoculated with hepatitis A virus. Infection of fibroblast cultures always resulted in an inapparent, persistent infection with production and release of infectious hepatitis A virus. Peripheral blood lymphocytes were collected from the same patients at different times after onset of icterus and were stored in liquid nitrogen. Cytolytic activity of peripheral blood lymphocytes was determined by a microcytotoxicity assay using autologous 51Cr-labeled hepatitis A virus-infected and uninfected target cells. Cytotoxic peripheral blood lymphocytes capable of lysing autologous hepatitis A virus-infected skin fibroblasts were detected in all patients with hepatitis A but were not demonstrable in the controls without antibodies against hepatitis A virus. The clinical course of the hepatitis A virus infection was normal in five patients; and in these patients, cytolytic activity of peripheral blood lymphocytes against hepatitis A virus-infected autologous targets peaked 2 to 3 weeks after onset of icterus. A clinically protracted form of the disease with persistent elevation of aminotransferases for at least 5 months after onset was present in two patients. In these cases, the highest cytolytic activity was demonstrated in peripheral blood lymphocytes collected 8 to 12 weeks after onset of icterus.(ABSTRACT TRUNCATED AT 250 WORDS)

Different baseline sister chromatid exchange levels in density fractionated human lymphocytes

Different activation states of B and T lymphocytes, as manifested by differences in cell density, were obtained by Percoll density centrifugation of unstimulated human lymphocytes. Four different density fractions were defined: B cells with low (1.043 g/ml) and high (1.056) density, and T cells with low (1.067) and high (1.077) density, respectively. Sister chromatid exchange (SCE) conditions and proliferation rates were determined. Total B cells, stimulated by the bacterial mitogen Branhamella, had 4.6 SCE per cell, the lowest mean baseline SCE level recorded among lymphocytes. The growth rate was intermediate between that of low and high density T cells. The two T cell fractions stimulated by phytohemagglutinin (PHA) had different baseline SCE frequencies and different growth characteristics: the low density cells had 5.7 SCEs per cell and a short cell cycle, whereas high density cells had 12.5 SCEs per cell and a longer cell cycle. The differences in baseline SCE frequency and growth characteristics between the two T cell fractions seem to be correlated with the differences in the activation state as reflected by the cell density. Both high and low density T cells are G0 populations which supposedly differ with respect to previous history in vivo such as age and contact with antigens. The reason why these cells react differently to bromodeoxyuridine (BrdU) is unknown, but differences in intracellular DNA precursor pools and enzyme activities might play a role.

Modulation of in vitro myelopoiesis by alloreactive T cell clones

Regulatory effects of mixed lymphocyte culture (MLC)-derived CD4+ human T cell clones on granulocyte-macrophage colony (CFU-GM) formation by normal bone marrow (BM) were studied in an initial attempt to establish an in vitro model for the negative feedback control of myelopoiesis by alloactivated T cells. This is likely to be of clinical significance in the aberrant control of haematopoiesis during some cases of graft-versus-host disease (GVHD) after allogeneic BM transplantation. Whilst 5 such alloproliferative clones generally failed to suppress CFU-GM, the majority of clones with natural killer (NK)-like activity, or those with suppressive activity in MLC, regularly and strongly suppressed in this system, reinforcing the view that certain T cells may have potent negative regulatory effects on haematopoiesis.

A procedure for the isolation of highly purified populations of B cells, T cells and monocytes from human peripheral and umbilical cord blood

A sequential separation protocol is described which reproducibly yields biologically active populations of B cells, T cells and monocytes from human peripheral and umbilical cord blood. The purification protocol employed T lymphocyte rosetting with unmodified sheep red blood cells, monocyte adherence to microexudate-coated flasks and anti-immunoglobulin panning of B cells. Population purity was determined by cytofluorographic light scatter analysis, expression of cell surface markers, esterase activity and mitogen responsiveness. The sequential protocol reproducibly yielded viable and functionally active cell populations of greater than 95% purity from a single starting population of mononuclear cells.

Dipeptidylaminopeptidase IV (DAP IV) activity in normal and malignant T-cell subsets as defined by monoclonal antibodies

The activity of dipeptidylaminopeptidase IV (DAP IV) was investigated by a cytochemical method in isolated fractions of normal peripheral blood mononuclear cells and malignant cells from 9 patients with chronic T-cell leukaemia. A positive DAP IV reaction was observed in 52% of normal T cells, a consistent negative reaction in normal B cells and monocytes. 2 distinct T-cell subsets, helper/inducer cells (T4+/T8-) and cytotoxic/suppressor cells (T4-/T8+), were negatively selected by complement-mediated cytolysis utilizing the monoclonal antibodies OKT4 and OKT8. On examination of these T-cell subsets a positive DAP IV reaction was restricted to the majority of normal T4+/T8- cells. The malignant cells from 3 patients with T-chronic lymphocytic leukaemia, expressing the cytotoxic/suppressor phenotype (T4-/T8+) lacked DAP IV activities. In contrast, almost all leukaemic cells from 3 other cases, expressing the helper/inducer phenotype (T4+/T8-), were strongly positive. Despite their T4+/T8- phenotype, the malignant cells from 3 patients with Sézary syndrome were completely DAP IV negative. These findings suggest that the DAP IV reaction may be helpful in the further characterization of normal and malignant T-cell subsets.

Alpha naphthyl acetate esterase in human blood cells with different molecular weights

Normal human blood cells contain esterases which hydrolyze alpha-naphthyl acetate (alpha NA). Purified preparations of these cells were investigated by polyacrylamide gradient gel electrophoresis at pH 9.0 and subsequent staining of gels for esterase activity. Extractable alpha NA esterase was separated according to molecular weight. alpha NA esterase with molecular weight of 55 000 was observed only in lymphocytes and red cells. Lymphocytes from patients with B-cell chronic lymphocytic leukemia (B-CLL) showed alpha NA esterase with molecular weight of 45 000 instead of 55 000. Esterases with molecular weights of 60 000 and 70 000 were detected in granulocytes monocytes and red cells. Only platelets and red cells exhibited alpha NA esterase with molecular weight of 80 000. alpha NA esterases with molecular weight of 290 000 could be demonstrated in granulocytes and red cells. All blood cells contained esterase with molecular weight of 360 000. alpha NA esterase with molecular weight of 390 000 was detected only in red cells. In all blood cells (without lymphocytes) esterase with molecular weight of 500 000 was demonstrated. Only the enzyme in monocytes, granulocytes and red cells was sensitive to fluoride inhibition.

Two distinct Fc receptors for IgG on human peripheral T lymphocytes

The proportion of human peripheral T lymphocytes forming rosettes with IgG-coated ox erythrocytes (ORBC) is increased after controlled hypotonic treatment. This increment may be as high as 40% of total T cells, depending on the lymphocyte donor. Such treatment is shown not to result in selective cell loss. Induced rosetting is mediated by a receptor specific for the Fc portion of human IgG (Fc gamma R). Inhibition of induced Fc gamma R activity is equally well accomplished by monomeric and by aggregated IgG of defined size. This is in contrast to the Fc gamma R detected before hypotonic treatment, which is not significantly inhibited by monomeric IgG. Capping studies established the structural independence of these two types of Fc gamma R in the lymphocyte membrane by virtue of selective cross-linking of either receptor while leaving the respective counterpart unaffected. The biochemical basis of the hypotonic effect is not yet resolved. However, the data presented suggest that hypotonicity results in removal of Fc gamma R-bound cytophilic IgG. Operationally, we propose the term induced Fc gamma R (Fc gamma R-I) for the here-described new type of receptor with high affinity for monomeric IgG.Fc gamma R that are directly assayable without hypotonic induction and not inhibited by monomeric IgG are termed free Fc gamma R (Fc gamma R-F).

A two-step procedure for obtaining normal peripheral blood T-lymphocytes using continuous equilibrium density gradient centrifugation on percoll

Equilibrium centrifugation of either peripheral blood mononuclear cells or of pure lymphocytes (obtained by carbonyl iron or glass bead adherence removal of monocytes) on a continuous density gradient of Percoll yielded lymphocyte fractions containing between 92 and 99% T lymphocytes as shown by sheep red blood cell rosetting. B lymphocytes with surface immunoglobulin were found in the regions of low density (1.03-1.065 g/ml) and T lymphocytes in the regions of higher density (1.06-1.08 g/ml). TM lymphocytes with their characteristic positive 'dot' pattern of staining for non-specific esterase were also found mainly in regions of high density. It was concluded that Percoll continuous equilibrium density gradient centrifugation can be used to obtain T lymphocytes in high yield, with high viability and without metabolic changes which may occur after contact with sheep red blood cells. The esterase staining suggested that there was also some separation of T lymphocyte subsets.

A subset of human cells isolated and characterized by monoclonal antibodies

Monoclonal antibodies were induced against leukemic T cells from a patient with chronic lymphocytic leukemia exhibiting natural killer (NK) activity. Two antibodies, termed T811 and M522, reacted by indirect immunofluorescence with distinct sub-populations of normal human mononuclear blood cells. The antibody T811 defines a surface antigen which is restricted to a subset of the T cell lineage. The antigen recognized by the second antibody, M522, is expressed on monocytes and polymorphonuclear leukocytes and, in addition, on 9-17% of nonadherent peripheral blood leukocytes (NAL). It is shown that the total NK activity of NAL is confined to the subset of cells expressing the M522-defined antigen. Moreover, the portion of NK cytotoxicity associated with T lymphocytes is mediated by a subpopulation which is characterized by the simultaneous expression of the T811- and the M522-defined antigens. This population comprises about 4% of NAL and could be isolated to a purity of greater than 85%.

Natural and antibody-dependent cellular cytotoxicity in tumour-adherent T lymphocytes: expression of Fc receptors and of a human T-subgroup-specific antigen

Adherence of human lymphocytes to allogeneic tumour cell monolayers was found to depend on the presence of monocytes. Adherent lymphocytes could be separated from tumour cells by treatment with lidocaine followed by nylon wool passage. Tumour-adherent cells (70% E-RFC, 45% Fc gamma-R, 23% Fc mu-R, 5% monocytes) exhibited enriched natural killer (NK) activity not only against the tumour cell line used for isolation but also against seven other targets. When T cells were isolated subsequently as E-rosettes by density gradient centrifugation through Percoll, the enrichment in cytotoxicity was even more pronounced. Tumour-adherent T cells were severalfold enriched in both NK and antibody-dependent cell-mediated cytotoxicity (ADCC) activity. However, this enrichment was not paralleled by a concomitant increase in the number of T gamma cells (tumour-adherent T cells: 17% T gamma, 40% T mu ; tumour-nonadherent T cells: 12% T gamma, 60% T mu). Marked differences could be observed by staining with a monoclonal antibody that was raised against human leukaemic T gamma cells of high NK and ADCC activity. This antibody (T 8-11) stained 60% of tumour-adherent T cells, 20% of nonadherent T cells and 29% of T-cell controls. These results indicate that the spontaneous cytotoxic activity of human T cells resides within a small population, most of which are characterized by a specific surface antigen but not by conventional Fc gamma receptors.

Human T cell differentiation antigens characterizing a cytotoxic/suppressor T cell subset

Monoclonal antibodies were raised against the leukemic T cells from a patient with chronic lymphocytic leukemia. Two antibodies, termed T411 and T811, were obtained which were reactive by indirect immunofluorescence only with cells of the T cell lineage. The T411 antibody recognized a polypeptide chain of 100,000 dalton apparent molecular weight which was present on the surface of 94 +/- 4% of peripheral blood T lymphocytes, but only on 20 +/- 8% of thymus cells. The antibody T811 reacted with a surface molecule composed of 2 poly-peptide chains of 32,000 and 34,000 dalton apparent molecular weight, which was expressed only on 25 +/- 10% of blood T lymphocytes and on 90 +/- 4% of thymus cells. Functional analysis of the T811+ and T811- T cell subsets isolated by rosetting with anti-mouse Ig coated ox erythrocytes revealed that both subpopulations were able to mount a proliferative response to allo-antigens, whereas allo-antigen induced cytotoxic cells and their precursors were only found in the T811+ subset. The pokeweed mitogen induced in vitro differentiation of B lymphocytes into immunoglobulin secreting cells was dependent on the presence of the T811- subset, whereas the T811+ T cells efficiently suppressed this differentiation.