A Thy-1.1-specific monoclonal alloantibody activates both mouse and rat T cells

Bleomycin-Treated Chimeric Thy1-Deficient Mice with Thy1-Deficient Myofibroblasts and Thy-Positive Lymphocytes Resolve Inflammation without Affecting the Fibrotic Response

Lung fibrosis is characterized by abnormal accumulation of fibroblasts in the interstitium of the alveolar space. Two populations of myofibroblasts, distinguished by Thy1 expression, are detected in human and murine lungs. Accumulation of Thy1-negative (Thy1(-)) myofibroblasts was shown in the lungs of humans with idiopathic pulmonary fibrosis (IPF) and of bleomycin-treated mice. We aimed to identify genetic changes in lung myofibroblasts following Thy1 crosslinking and assess the impact of specific lung myofibroblast Thy1-deficiency, in vivo, in bleomycin-injured mouse lungs. Thy1 increased in mouse lung lymphocytes following bleomycin injury but decreased in myofibroblasts when fibrosis was at the highest point (14 days), as assessed by immunohistochemistry. Using gene chip analysis, we detected that myofibroblast Thy1 crosslinking mediates downregulation of genes promoting cell proliferation, survival, and differentiation, and reduces production of extracellular matrix (ECM) components, while concurrently mediating the upregulation of genes known to foster inflammation and immunological functions. Chimeric Thy1-deficient mice with Thy1(+) lymphocytes and Thy1(-) myofibroblasts showed fibrosis similar to wild-type mice and an increased number of CD4/CD25 regulatory T cells, with a concomitant decrease in inflammation. Lung myofibroblasts downregulate Thy1 expression to increase their proliferation but to diminish the in vivo inflammatory milieu. Inflammation is not essential for evolution of fibrosis as was previously stated.

Immune system cell markers in the northern brown bandicoot, Isoodon macrourus

This is the first study to report the presence of T and B lymphocyte markers and antigen presenting-like molecules in a marsupial bandicoot. Intra-cytoplasmic markers for CD3 and CD5, as well as surface Thy-1.1 and CD1a molecules were located in lymphocytes of T dependent regions of immuno-lymphoid tissue in the northern brown bandicoot using immunohistochemical techniques. Similarly, intra-cytoplasmic domains of CD79a, CD79b molecules and surface IgG molecules enabled characterisation of B lymphocytes and plasma cells. The phenotypic expression of these molecules parallels findings in eutherians, suggesting firstly the conservation of lineage epitopes for T and B subsets and secondly, the potential for similar functional properties of immune system cells between marsupials and eutherians. In addition, the presence of MHC class II and CD1a molecules on dendritic-like cells may indicate similar mechanisms for antigen processing and presentation as reported in eutherians. The use of such immune system cell markers will enable functional studies to characterise the marsupial immune system as well as ontogeny studies of immune competence.

An astrocytic binding site for neuronal Thy-1 and its effect on neurite outgrowth

Thy-1, a member of the immunoglobulin superfamily, is one of the most abundant glycoproteins on mammalian neurons. Nevertheless, its role in the peripheral or central nervous system is poorly understood. Certain monoclonal antibodies to Thy-1 promote neurite outgrowth by rodent central nervous system neurons in vitro, suggesting that Thy-1 functions, in part, by modulating neurite outgrowth. We describe a binding site for Thy-1 on astrocytes. This Thy-1-binding protein has been characterized by immunofluroesence with specific anti-idiotype monoclonal antibodies and by three competitive binding assays using (i) anti-idiotype antibodies, (ii) purified Thy-1, and (iii) Thy-1-transfected cells. The Thy-1-binding protein may participate in axonal or dendritic development in the nervous system.

Second messenger-induced modulation of Thy-1 antigen expression: an ELISA study using murine thymic and neuroblastoma cells

Freshly isolated cells of murine thymuses and in vitro cultured murine neuroblastoma cells were seeded into microplates, treated with either phorbol myristate acetate (PMA) or dibutyryl-cyclic adenosine monophosphate (DBcAMP), and then processed for enzyme immunoassay to analyze with G4 monoclonal antibody the expression of Thy-1.2 antigen epitope. Pretreatment of thymic cells with PMA resulted in little, if any, decrease of Thy-1 expression, while treatment of these cells with DBcAMP caused a significant down-modulation of the epitope. DBcAMP did not affect binding of another murine IgG antibody to the thymic cells. Modulation of the epitope on thymic cells caused by DBcAMP was dose-dependent with maximal effect seen at the drug concentration of 10(-4) M. However, at various doses of DBcAMP (10(-6) to 10(-3) M) we were unable to detect any significant shift of Thy-1 expression on neuroblastoma cells. Though mechanisms of the above phenomena need further elucidation, we conclude that cellular ELISA may provide a useful alternative to more commonly used cytofluorimetric studies for the analysis of immune cell-surface antigen expression and its pharmacological and physiological modulation.

T cell activation: distinct pathways involve phosphorylation of different cellular proteins

The murine T cell clone D10.G4.1 can be induced to proliferate by monoclonal antibodies (mAb) to the T cell receptor (TcR) or to Thy-1 molecules. When cells were stimulated by anti-TcR mAb, a group of 4 proteins (19-25 kDa) was specifically phosphorylated. This effect was completely mimicked by the Ca2+ ionophore A23187, whereas only two of these proteins (19 kDa and 25 kDa) were phosphorylated after cell exposure to the phorbol ester 12-O-tetradecanoylphorbol 13-acetate. By contrast, anti-Thy-1 mAb had no effect on the phosphorylation of these proteins, but induced specifically the phosphorylation of a protein of 32 kDa. These results therefore demonstrate that distinct activating pathways in T cells involve the phosphorylation of different proteins, suggesting that the stimulation of protein kinases in T lymphocytes is an early event in cell activation.

Interactions between the Thy-1 and T-cell antigen receptor pathways in the activation of cytotoxic T cells: evidence from synergistic effects, loss variants, and anti-CD8 antibody-mediated inhibition

The relationship between activation of cytolytic T-lymphocyte (CTL) clones via the T-cell receptor (Ti) or the Thy-1 molecule was investigated. Anti-Ti and anti-Thy-1 monoclonal antibodies (mAb) can activate CTL clones to secrete interferon-gamma (IFN-gamma). Suboptimal doses of anti-Ti and anti-Thy-1 mAb, as well as suboptimal doses of two different anti-Thy-1 mAb, can synergize to activate T-cell clones. The addition of phorbol myristic acetate (PMA), which is not stimulatory by itself, can enhance the synergistic effect of mAb on IFN-gamma production. Although the Ti and Thy-1 molecules were not found associated at the cell surface, the results presented here indicate that these molecules are functionally associated. Use of Ti loss variants of a CTL clone confirms that Thy-1-mediated signaling is not an alternative to, but is dependent on the Ti-mediated activation pathway. Additionally, use of anti-Lyt-2/3 mAb, previously described as interfering with class I MHC-Ti binding and/or activation and, in some cases, with anti-Ti-mediated activation revealed that anti-Thy-1 mAb-mediated activation was also greatly reduced by the presence of Lyt-2/3-specific mAb. Thus the interaction between Thy-1 and Ti might also involve Lyt-2 (Lyt-3) molecules.

Evidence that murine hematopoietic cell subset marker J11d is attached to a glycosyl-phosphatidylinositol membrane anchor

Glycosyl-phosphatidylinositol (G-PI) has been shown to serve as membrane anchor for cell surface molecules such as Thy-1, Ly-6-controlled ThB and Qa antigens. Here, we present several lines of evidence indicating that the hematopoietic cell lineage (i.e. thymocytes, B cell subset and red blood cells) marker defined by the rat monoclonal antibody J11d is also a G-PI-linked structure. First, surface expression of the J11d-defined molecules, and that of the related antigen B2A2, was found to be specifically reduced by treatment of thymocytes and B lymphoma or hybridoma cells with excess of Staphylococcus aureus PI-specific phospholipase C; this enzyme also solubilizes a 35-40-kDa material from erythrocyte microsomal membranes corresponding to the predominant J11d-reactive red cell surface molecules. Second, Thy-1- mutants of the BW5147, T1M1, S1A or S49 murine T lymphoma cells of the complementary classes A, B, C and E (i.e. shown to be defective in the enzymatic machinery that posttranslationally modify Thy-1 molecules) also lack J11d, or express it at a very low level. Although directed at a G-PI-linked structure, the J11d monoclonal antibody, unlike other reagents to Thy-1 or Ly-6-controlled antigens, failed to induce thymocyte proliferation even in the presence of phorbol myristate acetate and cross-linker monoclonal antibody.

Thy-1 solubilization from mouse T cells by phosphatidylinositol-specific phospholipase C: biochemical and antigenic characterization

Membrane anchorage of mouse and rat Thy-1 antigens results from the post-translational attachment of a non-proteic tail terminated by a phosphatidylinositol group. In order to determine the biochemical and antigenic properties of the material released by phosphatidylinositol-specific phospholipase C (PI-PLC), we studied, by one-(1-D) and two-dimensional (2-D) gel electrophoresis and by immunoprecipitation, the supernatant of surface-labelled mouse T cells treated with purified Staphylococcus aureus PI-PLC. The major protein released by this enzymatic treatment showed an apparent molecular weight (MW) and an isoelectric focusing (IEF) pattern identical to those of detergent-solubilized, immunoprecipitated Thy-1. In addition, a sandwich radioimmunoassay (RIA) utilizing two Thy-1-specific monoclonal antibodies (mAb) was used to quantitate the amounts of PI-PLC-released and spontaneously shed Thy-1. Considerable differences in susceptibility to enzymatic cleavage and in spontaneous shedding were observed for a variety of mouse T-cell populations, including thymocytes and hybridoma, helper and cytotoxic cloned T cells, even though time-course experiments demonstrated that excess enzyme was used. It might be useful to consider these differences in the cell biology of Thy-1 and the occurrence of other PI-linked proteins of the lymphocyte surface in terms of their implications in the transduction of activation signals.