Concurrent zero-dimensional and one-dimensional biomineralization of gold from a solution of Au3+ and bovine serum albumin

A technique was developed for preparing a novel material that consists of gold nanoparticles trapped within a fiber of unfolded proteins. These fibers are made in an aqueous solution that contains HAuCl4 and the protein, bovine serum albumin (BSA). By changing the ratio of gold to BSA in solution, two different types of outcomes are observed. At lower gold to BSA ratios (30-120), a purple solution results after heating the mixture at 80 °C for 4 h. At higher gold to BSA ratios (130-170), a clear solution containing purple fibers results after heating the mixture at 80 °C for 4 h. UV-Vis spectroscopy and light scattering techniques show growth in nanocolloid size as gold to BSA ratio rises above 100. Data indicate that, for the higher gold to BSA ratios, the gold is sequestered within the solid material. The material mass, visible by eye, appears to be an aggregation of smaller individual fibers. Scanning electron microscopy and transmission electron microscopy indicate that these fibers are primarily one-dimensional aggregates, which can display some branching, and can be as narrow as 400 nm in size. The likely mechanism for the synthesis of the novel material is discussed.

In situ leukemic plasmacytoid dendritic cells pattern of chemokine receptors expression and in vitro migratory response

Plasmacytoid dendritic cell (PDC) leukemia/lymphoma is a rare neoplasm presenting cutaneous lesions at the time of diagnosis, followed by dissemination to bone marrow, lymph nodes, and other lymphoid and nonlymphoid organs. Since these leukemic counterparts of human PDC are similar to normal PDC, we studied their chemokine receptor equipment and their migratory capacities. We found both in skin lesions and in invaded lymph nodes an expression by tumor cells of CXCR3, CXCR4, and CCR7, and the concomitant expression by cells in the microenvironment of their respective ligands CXCL9, CXCL12, and CCL19. Moreover, flow cytometry phenotype of leukemic PDC (LPDC) revealed an unexpected expression of CCR6. We show that fresh tumor cells are able to migrate in response to CXCR4, CCR2, CCR5, CCR6, and CCR7 ligands, and the ability of CXCR3 ligands to increase the responsiveness to CXCL12. IL-3- or virus-induced activation of LPDC leads to downregulation of CXCR3 and CXCR4, and upregulation of CCR7, associated with the loss of response to CXCL12, and the acquisition of sensitivity to CCL19. Altogether, these results suggest that the preferential accumulation of LPDC in the skin or lymph nodes could be orchestrated by CXCR3, CXCR4, CCR6, and CCR7 ligands, found in nontumoral structures of invaded organs.

Immunobiology of dendritic cells

Dendritic cells (DCs) are antigen-presenting cells with a unique ability to induce primary immune responses. DCs capture and transfer information from the outside world to the cells of the adaptive immune system. DCs are not only critical for the induction of primary immune responses, but may also be important for the induction of immunological tolerance, as well as for the regulation of the type of T cell-mediated immune response. Although our understanding of DC biology is still in its infancy, we are now beginning to use DC-based immunotherapy protocols to elicit immunity against cancer and infectious diseases.

CD40 expression by human bronchial epithelial cells

CD40 is a 50-kDa protein expressed on B cells, dendritic cells, monocytes and epithelial cells, but the distribution of CD40 expression in humans is not completely known. It binds to a ligand (CD40L) which is expressed essentially on activated T cells. The interaction between CD40 and CD40L plays important roles in immune responses. CD40 expression was investigated on bronchial tissues and human bronchial cell lines using immunohistochemistry, immunofluorescence staining and analysis with a cytometer, respectively. Constitutive CD40 expression, but not that of CD40L, was slightly detectable on normal human bronchial epithelial cells (HBEC) in situ and on an adult lung adenocarcinoma (SKLU1) cell line, while another cell line, a bronchial transformed SV40 cell line (WI26VA4), was negative for CD40. Among the various cytokines tested, only interferon (IFN)-gamma was found to induce CD40 expression on WI26VA4. Tumour necrosis factor (TNF)-alpha was the best cytokine able to up-regulate CD40 in SKLU1 cells. A combination of IFN-gamma and TNF-alpha was slightly more effective than the cytokine alone at up-regulating CD40 expression on both cell lines. We further investigated the functional consequences of CD40 ligation on both cell lines. These bronchial cells expressed CD40, HLADR and CD54 under basal conditions or when stimulated by cytokines. Stimulation through CD40 did not affect cell-surface-antigen expression on either cell line. The production of cytokines such as interleukin (IL)-6 and granulocyte macrophage-colony stimulating factor (GM-CSF) by HBEC has been described. SKLU1 and WI26VA4 cells released IL-6 and GM-CSF spontaneously. Whatever the case, CD40 engagement did not modulate spontaneous or TNF-alpha-induced production of these two cytokines. These data indicate for the first time that normal HBEC express CD40 in situ. Further investigations are required in order to determine the role of CD40 on normal HBEC.

Reciprocal control of T helper cell and dendritic cell differentiation

It is not known whether subsets of dendritic cells provide different cytokine microenvironments that determine the differentiation of either type-1 T helper (TH1) or TH2 cells. Human monocyte (pDC1)-derived dendritic cells (DC1) were found to induce TH1 differentiation, whereas dendritic cells (DC2) derived from CD4+CD3-CD11c- plasmacytoid cells (pDC2) induced TH2 differentiation by use of a mechanism unaffected by interleukin-4 (IL-4) or IL-12. The TH2 cytokine IL-4 enhanced DC1 maturation and killed pDC2, an effect potentiated by IL-10 but blocked by CD40 ligand and interferon-gamma. Thus, a negative feedback loop from the mature T helper cells may selectively inhibit prolonged TH1 or TH2 responses by regulating survival of the appropriate dendritic cell subset.

Efficient recombination of a switch substrate retrovector in CD40-activated B lymphocytes: implications for the control of CH gene switch recombination

Maturing B lymphocytes possess a recombination activity that switches the class of heavy chain Ig. The nature of the recombination activity, its molecular requirements and regulation remain elusive questions about B lymphocyte biology and development. Class switch recombination is controlled by cytokine response elements that are required to differentially activate CH gene transcription before their subsequent recombination. Here, we show that cultures of purified murine and human B cells, stimulated only by CD40 receptor engagement, possess a potent switch recombination activity. CD40 ligand-stimulated murine and human B lymphocytes were infected with recombinant retroviruses containing Smu and S gamma 2b sequences. Chromosomally integrated switch substrate retrovectors (SSRs), harboring constitutively transcribed S sequences, underwent extensive recombinations restricted to their S sequences with structural features akin to endogenous switching. SSR recombination commenced 4 days postinfection (5 days poststimulation) with extensive switch sequence recombination over the next 2 to 3 days. In contrast, endogenous S gamma 2b and S gamma 1 sequences did not undergo appreciable switch recombination upon CD40 signaling alone. As expected, IL-4 induced endogenous Smu to S gamma 1 switching, while endogenous Smu to S gamma 2b fusions remained undetectable. Surprisingly, IL-4 enhanced the onset of SSR recombination in CD40-stimulated murine B cells, with S-S products appearing only 2 days postinfection and reaching a maximum within 2 to 3 days. The efficiency of switch recombination with SSRs resembles that seen for endogenous C(H) class switching.

Polymerase chain reaction selects a novel disintegrin proteinase from CD40-activated germinal center dendritic cells

To identify genes expressed by a specific subset of dendritic cells found in vivo a polymerase chain reaction-based cDNA subtraction technique was applied to the recently described germinal center dendritic cells. A novel member of the disintegrin metalloproteinase family was cloned which comprises a not typical zinc-chelating catalytic site most similar to a bacterial metalloproteinase. Dendritic cell precursors or immature dendritic cells express no or low levels of the message. It is induced to high levels upon spontaneous or CD40-dependent maturation and in a mixed lymphocyte reaction. In situ hybridization showed distinct expression of this gene in the germinal center. This, together with the findings that certain disintegrin metalloproteinases regulate the activity of tumor necrosis factor alpha and that metalloproteinases have also been implicated in FasL processing, suggest that this novel molecule may play an important role in dendritic cell function and their interactions with germinal center T cells.

The EBV IL-10 homologue is a selective agonist with impaired binding to the IL-10 receptor

BCRF1 is an EBV homologue of human IL-10 (hIL-10) and is known as viral IL-10 (vIL-10). As found earlier for the effects of vIL-10 on mouse mast cells and CD4+ T cells, the efficiency of inhibition by vIL-10 of IL-2 production by human CD4+ T cell clones is approximately 1000-fold diminished compared with hIL-10. We studied the interaction of vIL-10 and an epitope-tagged homologue, vIL-10His6, with recombinant mouse and human IL-10 receptors (mIL-10R, hIL-10R). vIL-10His6 has approximately 1000-fold lower affinity for recombinant IL-10R than does hIL-10, yet stimulates proliferation of mouse Ba/F3 (BaF)-mIL-10R- and human TF1-hIL-10R-transfected cells with a sp. act. comparable to or greater than that of the cellular cytokine. In contrast, BaF-hIL-10R cells are approximately 1000-fold less sensitive to vIL-10His6 than are BaF-mIL-10R cells. An anti-hIL-10R mAb (3F9) blocks responses to both hIL-10 and vIL-10His6, while a soluble form of hIL-10R effectively neutralizes biologic responses only to hIL-10 by both BaF-IL-10R transfectants and normal human peripheral blood cells. The results indicate that biologic responses to both hIL-10 and vIL-10 require the known IL-10R, and suggest the existence of at least one additional IL-10R subunit. We suggest that vIL-10 is a selective agonist that is impaired in its ability to bind the defined IL-10R, which we now designate as IL-10R alpha.

The EBV IL-10 homologue is a selective agonist with impaired binding to the IL-10 receptor

BCRF1 is an EBV homologue of human IL-10 (hIL-10) and is known as viral IL-10 (vIL-10). As found earlier for the effects of vIL-10 on mouse mast cells and CD4+ T cells, the efficiency of inhibition by vIL-10 of IL-2 production by human CD4+ T cell clones is approximately 1000-fold diminished compared with hIL-10. We studied the interaction of vIL-10 and an epitope-tagged homologue, vIL-10His6, with recombinant mouse and human IL-10 receptors (mIL-10R, hIL-10R). vIL-10His6 has approximately 1000-fold lower affinity for recombinant IL-10R than does hIL-10, yet stimulates proliferation of mouse Ba/F3 (BaF)-mIL-10R- and human TF1-hIL-10R-transfected cells with a sp. act. comparable to or greater than that of the cellular cytokine. In contrast, BaF-hIL-10R cells are approximately 1000-fold less sensitive to vIL-10His6 than are BaF-mIL-10R cells. An anti-hIL-10R mAb (3F9) blocks responses to both hIL-10 and vIL-10His6, while a soluble form of hIL-10R effectively neutralizes biologic responses only to hIL-10 by both BaF-IL-10R transfectants and normal human peripheral blood cells. The results indicate that biologic responses to both hIL-10 and vIL-10 require the known IL-10R, and suggest the existence of at least one additional IL-10R subunit. We suggest that vIL-10 is a selective agonist that is impaired in its ability to bind the defined IL-10R, which we now designate as IL-10R alpha.

Identification of human IgG autoantibodies specific for IL-10

Since autoantibodies to IL-1alpha, interferon-alpha (IFN-alpha) and IL-6 have been described, this study concentrated on the search for autoantibodies to hIL-10 using an assay based on the precipitation of 125I-hIL-10 autoantibody complexes using Protein G-Sepharose. Among 1860 tested sera, only seven were found to specifically precipitate IL-10, thus indicating the rare occurrence of such autoantibodies. Four of those seven anti-IL-10 autoantibody sera were specific for hIL-10, two recognized both human and viral IL-10, while the last one recognized human, viral and murine IL-10, thus suggesting the existence of at least three different epitopic specificities. The purification of anti-IL-10 autoantibody from one serum demonstrated the existence of a single (IgG1, lambda) autoantibody that neutralized IL-10 biological activity. Thus, autoantibodies to IL-10 may represent natural antagonists to IL-10.

Human interleukin-6 acts as a co-factor for the up-regulation of C3 production by rat liver epithelial cells

We investigated the role of human interleukin-6 (IL-6) in the regulation of the third component of complement (C3) biosynthesis by cultured rat liver epithelial cells. A natural human IL-6 (nh IL-6) preparation was shown to up-regulate C3 production, whereas an Escherichia coli-derived recombinant human IL-6 (rh IL-6) displayed no activity on C3 biosynthesis. However, the C3-stimulating activity of the nh IL-6 preparation was only partially reduced when treated with an antihuman IL-6 monoclonal antibody. Binding studies indicated that although it was devoid of any C3 stimulating activity, rh IL-6 specifically bound to hepatic cell receptors (Kd = 0.38 nM) and possessed the same binding affinity as nh IL-6. Furthermore, the substitution of natural IL-6 molecules for the recombinant IL-6 led to the recovery of the initial C3-stimulating activity. These studies demonstrated that human IL-6 alone does not stimulate rat liver epithelial cell C3 production but is able to accentuate the C3-stimulating activity of unrecognized components which are present in the nh IL-6 preparation. Human IL-6 thus appears to act as a co-factor for the up-regulation of hepatic C3 production.

Spontaneous expression of a low affinity Fc receptor for IgA (Fc alpha R) on human B cell lines

Expression of receptors for IgA (Fc alpha Rs) was investigated on a panel of 35 human B cell lines by labelling with human secretory IgA (0.5 mg/ml) and flow cytometry analysis after staining with fluoresceinated goat anti-human secretory component and/or anti-alpha chain F(ab')2 fragments. Receptors for IgA could be demonstrated on one out of nine Burkitt's lymphoma cell lines, three out of five myeloma cell lines and five out of 21 lymphoblastoid cell lines. The percentage of Fc alpha R-positive cells within the same B cell line varied upon repeated examination. Human dimeric IgA1 lambda myeloma protein revealed the same number of IgA receptor positive cells as did secretory IgA, whereas monomeric IgA did not bind to Fc alpha R. Detection of Fc alpha R was not inhibited when the tests were carried out in the presence of human dimeric IgG, IgM, asialo-orosomucoid, and secretory component but it was abrogated by pre-treatment of the cells with trypsin. The binding characteristics of Fc alpha Rs were studied on the myeloma cell line Esteve, using 125I-labelled human dimeric IgA and secretory IgA. The binding was dose-dependent with rapid kinetics and specific inhibition by unlabelled secretory IgA. Scatchard plot analysis resulted in an equilibrium constant K ranging from 3.2 to 4.7 x 10(6) M/l. No correlation was observed between Fc alpha R expression and differentiation stage, monoclonality, polyclonality of the cell lines, or Ig class produced by the B cells.