118,023 research outputs found
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Down-regulation of IL-2 production by activation of T cells through Ly-6A/E
No full textLy-6A/E molecules are expressed on the surface of T cells and have been shown to function in activation by the capacity of anti-Ly-6A/E mAb to induce T cell hybridomas or normal T cells to produce IL-2. Recent evidence suggests that activation through Ly-6A/E may be linked to the TCR signaling pathway. To further investigate the relationship between Ly-6- and TCR-induced T cell activation, we have examined whether an anti-Ly-6A/E mAb (D7) modulates TCR signaling in vitro. We now report that mAb D7 specifically inhibited IL-2 production by T cells also activated through TCR. Such inhibition was noted for normal T cells stimulated by soluble anti-CD3 or alloantigen and for T hybridomas stimulated by soluble anti-CD3. The ability of D7 to inhibit IL-2 production by T hybridomas was dependent on the nature of the TCR activating signal because IL-2 production was not inhibited when T hybridomas were stimulated with Ag or immobilized anti-CD3. Inhibition of IL-2 production by D7 apparently required cross-linking of the mAb because D7 F(ab')2 fragments were not effective for inhibition of IL-2 production. Similar to its ability to enhance anti-Ly-6A/E-induced activation of T and B cells, IFN-gamma enhanced the D7-induced inhibition of IL-2 production by alloantigen-activated normal T cells. These data further support the notion that Ly-6 and TCR signaling pathways are interrelated
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Activation of T lymphocytes through the Ly-6 pathway is defective in A strain mice
No full textThe Ly-6 alloantigens have been shown to participate in the process of T cell activation based on the ability of anti-Ly-6 mAb to induce IL-2 production and proliferation of T lymphocytes. In the present investigation we have demonstrated that peripheral T lymphocytes from A strain mice exhibited abnormally low proliferative responses after stimulation through Ly-6A/E and Ly-6C molecules when compared to responses of T cells from numerous other mouse strains. The abnormal activation of the Ly-6 pathway of A strain T cells was not due to ineffective FcR cross-linking of the anti-Ly-6 mAb, to inappropriate cellular expression of the Ly-6A/E alloantigen in A strain T cells, or to an active suppressive phenomenon. T lymphocytes from A strain mice proliferated normally when the cells were activated by mAb to Thy-1 or the CD3/TCR complex suggesting that A strain mice did not exhibit a generalized T cell activation defect. Cell separation studies of T cells and accessory cells demonstrated that this defect was quantitative, rather than qualitative, and that it was complex, residing at both the T cell and accessory cell levels. These results suggest that activation of T lymphocytes via the Ly-6 molecule may involve a signaling pathway and/or cell-cell interactions distinct from those required for optimal activation via CD3/TCR
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Distribution of Ly-6C on lymphocyte subsets: I. Influence of allotype on T lymphocyte expression
No full textThe expression patterns of the Ly-6C Ag were examined on splenic and thymic lymphocyte subsets of Ly-6.1 and Ly-6.2 strains of mice using the rat mAb 15.1. Ly-6C is expressed on subsets of CD4+ and CD8+ splenocytes, and a portion of NK cells. Within the splenic and lymph node CD4+ T cell compartment, Ly-6C expression is restricted to Ly-6.2 strains of mice, and is present on a subset of naive cells. Ly-6C is expressed on the majority of peripheral CD8+ T cells in both Ly-6.1 and Ly-6.2 strains, and is found primarily on the Ag-experienced subset. In the thymus, Ly-6C is present on subpopulations of CD4- CD8+, CD4- CD8-, and CD4+ CD8- cells. Ly-6C+ CD4- CD8+ thymocytes show a mature phenotype, while Ly-6C+ CD4- CD8- and Ly-6C+ CD4+ CD8- thymocytes appear to be part of the recently described NK1.1+ alphabeta TCR+ population. On account of the marked differences in Ly-6C expression on peripheral CD4+ T cells from Ly-6.1 and Ly-6.2 strains of mice, additional experiments were undertaken to assess Ly-6C expression in parental and Ly-6.1 x Ly-6.2 F1 mice. Neither phenotype dominated in the F1 offspring, with frequencies of Ly-6C+ CD4+ splenocytes falling in the intermediate range. Further experiments compared the staining patterns of the rat anti-pan Ly-6C (Ly-6.1 and Ly-6.2) Ab with a mouse anti-Ly-6.2 allotype specific Ab, with emphasis on both Ly-6.2 and Ly-6.1 x Ly-6.2 F1 mice. The results demonstrate the presence of lymphocytes that express the pan form of Ly-6C but not the form recognized by the alloantibody. This latter finding suggests the presence of more than one form of the Ly-6C Ag
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Multiple glycosylphosphatidylinositol-anchored Ly-6 molecules and transmembrane Ly-6E mediate inhibition of IL-2 production
No full textCross-linking of Ly-6 molecules on T lymphocytes leads to IL-2 production, whereas costimulation of T cells via Ly-6A/E and the TCR inhibits IL-2 secretion. This study was initiated to determine whether there are unique structural requirements at the level of the Ly-6 molecule for its capacity to activate or block IL-2 production. Functional studies in which transfected EL-4J cells that expressed various Ly-6 proteins or chimeric Ly-6 molecules were used have demonstrated that direct activation of IL-2 secretion or inhibition of anti-CD3-induced IL-2 production occurred after mAb binding to Ly-6A/E, Ly-6C, and Ly-6G and was independent of whether the mAbs bound to amino- or carboxyl-terminal epitopes of Ly-6. The blockade of IL-2 production by costimulation with anti-CD3 and anti-Ly-6 was detected even when the addition of either mAb was temporally delayed for up to 17 h in a reciprocal fashion. Stimulation of mouse Ly-6 proteins expressed in Jurkat cells antagonized PMA/OKT3-induced IL-2 production, thus revealing that the Ly-6 inhibitory pathway is operative in human cells. EL-4J cells were also transfected with a chimeric construct in which the glycosylphosphatidylinositol anchor of Ly-6E was replaced by the transmembrane and a portion of the intracytoplasmic tail of H-2Db. Anti-Ly-6A/E also blocked anti-CD3-induced IL-2 production for these cells, although anti-Ly-6A/E failed to directly induce IL-2 secretion. Thus, anti-Ly-6A/E blockade of IL-2 production is independent of the glycosylphosphatidylinositol anchor of Ly-6E. This finding suggests that there may be aspects of signaling via Ly-6 that are solely dependent on the extracellular amino acid sequence of this protein
Inhibition of Ly-6A antigen expression prevents T cell activation
No full textAntisense oligonucleotides complementary to the 5' end of the mRNA encoding the Ly-6A protein were used to block the expression of that protein. Using this approach we could inhibit the expression of Ly-6A by 60-80% in antigen-primed lymph node (LN) T cells as well as in the D10 T cell clone. Inhibition of Ly-6 expression resulted in the inability to restimulate in vitro, antigen-primed T cells. It also blocked the activation of normal spleen cells by Con A, monoclonal antibody (mAb) to CD3, and mAb to Ly-6. In contrast, stimulation of normal spleen cells with the pharmacological agents PMA + ionomycin were unaffected by the inhibition of Ly-6 expression. Similar results were obtained with the D10 T cell clone; stimulation with Con A + interleukin 1 (IL-1), antigen-presenting cells (APC), or the clonotypic antibody + IL-1 was greatly reduced in the presence of antisense oligonucleotides to Ly-6. Stimulation with PMA + ionomycin was again unaffected. We also studied the effect of antisense oligonucleotides on stimulation of preactivated D10 cells. Preactivation of D10 cells with Con A + IL-1 renders them receptive to secondary stimulation by other lymphokines. In this case, antisense oligonucleotides to Ly-6 had no effect on secondary activation with IL-2, IL-4 + IL-1, or PMA + ionomycin. We conclude from these studies that Ly-6 expression is required for T cell receptor (TCR)-mediated T cell activation
Plasticity of Ly-6Chi Myeloid Cells in T Cell Regulation
No full textAbstract
CD11b+Ly-6Chi cells, including inflammatory monocytes (IMCs) and inflammatory dendritic cells (IDCs), are important in infectious, autoimmune, and tumor models. However, their role in T cell regulation is controversial. In this article, we show that T cell regulation by IMCs and IDCs is determined by their activation state and is plastic during an immune response. Nonactivated IMCs and IDCs function as APCs, but activated IMCs and IDCs suppress T cells through NO production. Suppressive IMCs are induced by IFN-γ, GM-CSF, TNF-α, and CD154 derived from activated T cells during their interaction. In experimental autoimmune encephalomyelitis, CD11b+Ly-6Chi cells in the CNS are increasingly activated from disease onset to peak and switch their function from Ag presentation to T cell suppression. Furthermore, transfer of activated IMCs or IDCs enhances T cell apoptosis in the CNS and suppresses experimental autoimmune encephalomyelitis. These data highlight the interplay between innate and adaptive immunity: immunization leads to the expansion of Ly-6Chi myeloid cells initially promoting T cell function. As T cells become highly activated in the target tissue, they induce activation and NO production in Ly-6Chi myeloid cells, which in turn suppress T cells and lead to the contraction of local immune response.</jats:p
Ly-6C is a marker of memory CD8+ T cells.
No full textThis study examined long-term phenotypic and functional effects of TCR ligation in vivo. Flow cytometric analysis of T cells from mice treated with anti-CD3 revealed an increase in CD44 expression in both the CD4+ and CD8+ populations. The phenotypic changes were a result of TCR engagement, because treatment with staphylococcal enterotoxin B (SEB) resulted in a preferential increase in CD44 expression on the SEB-reactive V beta 8 T cells. In addition, the percentage of cells expressing Ly-6C increased among the CD8+ subset after anti-CD3 treatment and in the V beta 8+ CD8+ subset after treatment with SEB. Finally, the TCR transgenic (Tg) mouse strain 2C was used to confirm that the phenotypic changes can be induced by exposure to a physiologic ligand (H-2Ld). Before treatment, nearly all of the Tg+CD8+ cells were CD44low/Ly-6C-. Tg+ peritoneal exudate T cells isolated from mice challenged with P815 cells (H-2Ld) up-regulated Ly-6C and secreted higher levels of IFN-gamma on a per Tg+ CD8+ T cell basis after treatment. Taken together, these data indicate that in vivo TCR/CD3 engagement results in phenotypic and functional changes in T cells. Furthermore, Ly-6C expression correlates with an increase in IFN-gamma production after antigenic stimulation of CD8+ T cells, suggesting that it is a "memory" marker that correlates with Ag-specific functional changes in CD8+ T cells
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Role of Ly-6A/E and T cell receptor-zeta for IL-2 production. Phosphatidylinositol-anchored Ly-6A/E antagonizes T cell receptor-mediated IL-2 production by a zeta-independent pathway
No full textLy-6A/E molecules were originally implicated in regulation of T cell activation because anti-Ly-6A/E mAb induce IL-2 production. More recently we have shown that anti-Ly-6A/E also inhibits IL-2 production induced by anti-CD3. In the present study we used mutant and transfected cell lines that varied in expression of Ly-6A/E or TCR-zeta to test whether the positive and negative modulations of IL-2 production by anti-Ly-6A/E occur by distinct mechanisms. Anti-Ly-6A/E inhibited anti-CD3-induced IL-2 production for Ly-6E.1-transfected EL4J cells, but did not affect IL-2 production of the parental Ly-6A/E-negative EL4J cells. These results indicate that TCR-mediated IL-2 production can occur in the absence of Ly-6A/E expression and establish that anti-Ly-6A/E-induced inhibition of IL-2 production was the result of antibody binding to Ly-6A/E. As expected, MA5.8 (zeta-negative) or CT108 (zeta-truncated) variants of the 2B4.11 T cell hybridoma did not produce IL-2 when stimulated with anti-Thy-1 or anti-Ly-6A/E mAb. In contrast, anti-Ly-6A/E inhibited anti-CD3-induced IL-2 production by MA5.8 and CT108. Furthermore, anti-Ly-6A/E-induced IL-2 production was restored for zeta-transfected MA5.8. Thus, although induction of IL-2 by anti-Ly-6A/E depends on zeta expression, inhibition of IL-2 by anti-Ly-6A/E occurs by a zeta-independent mechanism. Interestingly, anti-Ly-6A/E, but not anti-Thy-1, inhibited anti-CD3-induced IL-2 production by MA5.8 and Ly-6E.1-transfected EL4J. Therefore, inhibition of IL-2 production by anti-Ly-6A/E was not a general property of a mAb binding to a phosphatidylinositol-linked molecule, as has been suggested for induction of IL-2 production. Taken together these data suggest that the molecular mechanisms of induction and inhibition of IL-2 production by anti-Ly-6A/E are separable and expression of TCR-zeta is one variable that distinguishes these two pathways
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