Annalisa Kunkl

Cytofluorometric methods for assessing absolute numbers of cell subsets in blood

The enumeration of absolute levels of cells and their subsets in clinical samples is of primary importance in human immunodeficiency virus (HIV)+ individuals (CD4+ T- lymphocyte enumeration), in patients who are candidates for autotransplantation (CD34+ hematopoietic progenitor cells), and in evaluating leukoreduced blood products (residual white blood cells). These measurements share a number of technical options, namely, single- or multiple-color cell staining and logical gating strategies. These can be accomplished using single- or dual-platform counting technologies employing cytometric methods. Dual-platform counting technologies couple the percentage of positive cell subsets obtained by cytometry and the absolute cell count obtained by automated hematology analyzers to derive the absolute value of such subsets. Despite having many conceptual and technical limitations, this approach is traditionally considered as the reference method for absolute cell count enumeration. As a result, the development of single-platform technologies has recently attracted attention with several different technical approaches now being readily available. These single-platform approaches have less sources of variability. A number of reports clearly demonstrate that they provide better coefficients of variation (CVs) in multicenter studies and a lower chance to generate aberrant results. These methods are therefore candidates for the new gold standard for absolute cell assessments. The currently available technical options are discussed in this review together with the results of some cross-comparative studies. Each analytical system has its own specific requirements as far as the dispensing precision steps are concerned. The importance of precision reverse pipetting is emphasized. Issues still under development include the establishment of the critical error ranges, which are different in each test setting, and the applicability of simplified low-cost techniques to be used in countries with limited resources.

CD8+CD28− T Regulatory Lymphocytes Inhibiting T Cell Proliferative and Cytotoxic Functions Infiltrate Human Cancers

Tumor growth is allowed by its ability to escape immune system surveillance. An important role in determining tumor evasion from immune control might be played by tumor-infiltrating regulatory lymphocytes. This study was aimed at characterizing phenotype and function of CD8+CD28− T regulatory cells infiltrating human cancer. Lymphocytes infiltrating primitive tumor lesion and/or satellite lymph node from a series of 42 human cancers were phenotypically studied and functionally analyzed by suppressor assays. The unprecedented observation was made that CD8+CD28− T regulatory lymphocytes are almost constantly present and functional in human tumors, being able to inhibit both T cell proliferation and cytotoxicity. CD4+CD25+ T regulatory lymphocytes associate with CD8+CD28− T regulatory cells so that the immunosuppressive activity of tumor-infiltrating regulatory T cell subsets, altogether considered, may become predominant. The infiltration of regulatory T cells seems tumor related, being present in metastatic but not in metastasis-free satellite lymph nodes; it likely depends on both in situ generation (via cytokine production) and recruitment from the periphery (via chemokine secretion). Collectively, these results have pathogenic relevance and implication for immunotherapy of cancer.

Multipotent mesenchymal stromal cells from amniotic fluid: solid perspectives for clinical application

Mesenchymal stromal cells are multipotent cells potentially useful in regenerative medicine. These cells are usually obtained from the bone marrow; however, the cell dose may be a critical factor, and alternative sources need to be explored. This study suggests that amniotic fluid represents a rich source of mesenchymal stromal cells. Background Mesenchymal stromal cells are multipotent cells considered to be of great promise for use in regenerative medicine. However, the cell dose may be a critical factor in many clinical conditions and the yield resulting from the ex vivo expansion of mesenchymal stromal cells derived from bone marrow may be insufficient. Thus, alternative sources of mesenchymal stromal cells need to be explored. In this study, mesenchymal stromal cells were successfully isolated from second trimester amniotic fluid and analyzed for chromosomal stability to validate their safety for potential utilization as a cell therapy product. Design and Methods Mesenchymal stromal cells were expanded up to the sixth passage starting from amniotic fluid using different culture conditions to optimize large-scale production. Results The highest number of mesenchymal stromal cells derived from amniotic fluid was reached at a low plating density; in these conditions the expansion of mesenchymal stromal cells from amniotic fluid was significantly greater than that of adult bone marrow-derived mesenchymal stromal cells. Mesenchymal stromal cells from amniotic fluid represent a relatively homogeneous population of immature cells with immunosuppressive properties and extensive proliferative potential. Despite their high proliferative capacity in culture, we did not observe any karyotypic abnormalities or transformation potential in vitro nor any tumorigenic effect in vivo. Conclusions Fetal mesenchymal stromal cells can be extensively expanded from amniotic fluid, showing no karyotypic abnormalities or transformation potential in vitro and no tumorigenic effect in vivo. They represent a relatively homogeneous population of immature mesenchymal stromal cells with long telomeres, immunosuppressive properties and extensive proliferative potential. Our results indicate that amniotic fluid represents a rich source of mesenchymal stromal cells suitable for banking to be used when large amounts of cells are required.

Human T-helper cell recognition of an immunodominant epitope of HIV-1 gp120 expressed on the surface of Streptococcus gordonii

Our genetic system for expression of heterologous proteins on the surface of the Gram-positive bacterium Streptococcus gordonii was used to express a human T-helper epitope of HIV-1 envelope glycoprotein gp120. In previous work on the naive repertoire of human T-helper cells, it was shown that a 15-amino acid synthetic peptide of the HIV-1 gp120 sequence contained an immunodominant T-helper epitope. Synthetic DNA coding for this peptide was cloned in frame within the gene for the streptococcal surface protein M6, and the gene fusion was integrated by transformation into the chromosome of S. gordonii. The expected M6-gp120 fusion protein was found to be expressed on the surface of the recombinant streptococci. To test whether the T epitope could be recognized by T cells when expressed on the bacterial surface within the context of M6, recombinant bacteria were used as antigen in proliferation assays to stimulate the 15-amino acid-specific human T-helper clone, in the presence of autologous antigen-presenting cells. Bacteria expressing the T epitope were efficiently recognized by the T cells in culture. In proliferation assays, 10(6)-10(7) bacteria induced responses comparable to those obtained by standard amounts of synthetic peptide (0.02-0.2 micrograms). Recombinant S. gordonii, a candidate for a live vaccine vector, appeared suitable for delivering T epitopes to the immune system.

High ERp5/ADAM10 expression in lymph node microenvironment and impaired NKG2D ligands recognition in Hodgkin lymphomas

Herein we describe that in classic Hodgkin lymphomas (cHL, n = 25) the lymph node (LN) stroma displayed in situ high levels of transcription and expression of the disulfide-isomerase ERp5 and of the disintegrin-metalloproteinase ADAM10, able to shed the ligands for NKG2D (NKG2D-L) from the cell membrane. These enzymes were detected both in LN mesenchymal stromal cells (MSCs) and in Reed-Sternberg (RS) cells; in addition, MIC-A and ULBP3 were present in culture supernatants of LN MSCs or RS cells. NKG2D-L-negative RS cells could not be killed by CD8(+)αβT or γδT cells; tumor cell killing was partially restored by treating RS cells with valproic acid, which enhanced NKG2D-L surface expression. Upon coculture with LN MSCs, CD8(+)αβT and γδT cells strongly reduced their cytolytic activity against NKG2D-L(+) targets; this seems to be the result of TGF-β, present at the tumor site, produced in vitro by LN MSCs and able to down-regulate the expression of NKG2D on T lymphocytes. In addition, CD8(+)αβT and γδT cells from the lymph nodes of cHL patients, cocultured in vitro with LN MSCs, underwent TGF-β-mediated down regulation of NKG2D. Thus, in cHL the tumor microenvironment is prone to inhibit the development of an efficient antitumor response.

Antigen‐presenting function of human peritoneum mesothelial cells

Mesothelial cells (MC) from human peritoneal omentum fragments obtained during surgical insertion of peritoneal catheters for continuous peritoneal dialysis in end stage renal failure (ESRF) patients were cultured in vitro. MC exhibited a phenotype different from macrophages, but MHC class II molecules were well expressed. Therefore MC lines were tested for antigen‐presenting capacity by pulsing with soluble antigens (tetanus toxoid and purified protein derivative (PPD)) or with a corpusculate antigen (Candida albicans bodies). Autologous peripheral blood mononuclear cells (PBMC) depleted of adherent monocytes and cloned T cells generated from an individual matched for the MHC class II antigen DR2 were used to test antigen‐presenting function. MC effectively presented the soluble and corpusculate antigens to autologous and MHC‐compatible allogeneic lymphocytes, indicating that they are endowed with both endocytic/phagocytic activity and with processing/presenting capacity. Preincubation of MC with human recombinant interferon‐gamma (IFN‐γ) up‐regulated MHC class II and intercellular adhesion molecule‐I (ICAM‐I) expression, but the effect on antigen‐presenting function was not consistent. Since MC are an important component of the peritoneal environment, they may participate, along with macrophages, in activation of specific T cells and in the generation of local cell‐mediated immunity to various pathogens.

Effects of cyclosporine on the immune system of the mouse. II. Cyclosporine inhibits the effector function of primary T helper cells, but not helper cell priming.

This paper describes various effects of cyclosporine on T helper (TH) cells for antibody production in the mouse. Immunosuppressive doses of cyclosporine abolish the help provided by virgin (primary) TH cells, but allow the priming of normal (and under certain conditions supranormal) numbers of TH cells as assayed by adoptive transfer experiments. The helper function of primed (secondary) TH cells is normally resistant to cyclosporine. However, if T cells are exposed to cyclosporine during priming their helper function remains totally cyclosporine-sensitive as long as the drug therapy is continued. The mechanisms involved in these selective effects are unknown, but the results indicate that in vivo cyclosporine can dissociate effector function (primary help) from TH cell proliferation (priming).

Biosafety guidelines for sorting of unfixed cells

The International Society of Analytical Cytology (ISAC) Biohazard Working Group presents guidelines for sorting of unfixed cells, including known biohazardous samples, using jet-in-air, deflected-droplet cell sorters. There is a risk that personnel operating these instruments could become exposed to droplets and aerosols containing biological agents present in the samples. The following guidelines can aid in the prevention of exposures of laboratory personnel to pathogens contained in the sort samples. The document provides biosafety recommendations for sample handling, operator training and protection, laboratory facility design, and instrument setup and maintenance. In addition, it describes in detail methods for assessment of instrument aerosol containment. Recommendations provided here may also help laboratories to obtain institutional and/or regulatory agency approval for sorting of unfixed and known biohazardous samples.

Inhibition of the accessory function of murine macrophages in vitro by cyclosporine

The accessory function of macrophages, which is strictly related to the induction of T cell activation, has been studied to determine whether it is affected by cyclosporine (CsA). Irradiated spleen cells, used as a source of macrophages, were pulsed overnight with β-galactosidase (GZ) in the presence of CsA. After washing of the pulsed macrophages, cells from a GZ-specific T cell line were added to cultures and 3H-thymidine incorporation was measured 72 hr later. We found that 500 ng/ml CsA present during macrophage pulsing with GZ reduced T cell proliferation to 5%. On the other hand, 100 ng/ml CsA almost completely abrogated the proliferative response when present for the duration of the culture. Similar results were also obtained using antigen-pulsed peritoneal-adherent macrophages to stimulate the T cell line to proliferate, or a T hybridoma clone to produce interleukin-2 (IL-2). The possibility that CsA actually affects interleukin-1 (IL-1) production by macrophages by inhibiting uninvolved T cells could be ruled out. We conclude that CsA-induced inhibition of T cell functions (proliferation and IL-2 production) is partially due to the effect of the drug on the accessory function of macrophages. This immunosuppressive mechanism of action of CsA on macrophages has not been previously described.

Recognition of Antigenic Clusters of Candida albicans by T Lymphocytes from Human Immunodeficiency Virus-Infected Persons

The fine specificity of the cellular immune response to Candida albicans (i.e., recognition of different antigenic components) between normal controls and human immunodeficiency virus-infected patients in various stages of disease was compared. C. albicans-specific T cells, enriched by antigen stimulation and interleukin-2 expansion, were challenged with antigenic fractions of different molecular weight obtained by SDS-gel fractionation of C. albicans extracts in the presence of autologous mononuclear cells as antigen-presenting cells. Proliferative responses showed similar patterns of reactivity between controls and category A and B seropositive subjects. Category C patients with concurrent C. albicans infections did not give rise to C. albicans-specific T cell lines, confirming the T cell defect. Patients without clinically evident C. albicans infection had a low but broad reactivity pattern of C. albicans-specific T cells. These results suggest that depletion of C. albicans-specific T cells, independent of their fine specificity, occurs along with disease progression.