bluuebunny/crossref_metadata_2025_split huggingface dataset:
Variations in the number of peptide-MHC class I complexes required to activate cytotoxic T cell responses.
Authors: Kageyama S , Tsomides T J , Sykulev Y , Eisen H N 
Published: December 2022

Abstract
We determined equilibrium constants for the binding of 16 peptides (based on four T cell epitopes) to three MHC class I proteins (A2, Kb, and Ld) on intact cells and estimated the number of accessible peptide-binding sites on these cells. From these results, and the concentrations of peptides required to sensitize target cells for lysis by CD8+ CTL, we conclude that the critical number of peptide-MHC complexes required per target cell for the activation of CTL responses varies with different combinations of peptide-MHC complexes and CTL clones from several thousand complexes to fewer than ten per target cell.
Oligomeric IgD augments and monomeric IgD inhibits the generation of IgG memory antibody responses in normal, but not in IgD-deficient, mice.
Authors: Swenson C D , Rizinashvili E , Amin A R , Thorbecke G J 
Published: December 2022

Abstract
Dimeric or aggregated IgD causes augmentation of primary and secondary Ab responses in mice when injected a few days before or together with the primary dose of Ag. This effect is mediated by Th cells and seems to be linked to the up-regulation of receptors for IgD on CD4+ T cells. IgD-R cross-linking is needed for receptor up-regulation. Here we show that addition of monomeric IgD to dimeric or aggregated IgD blocks IgD-R up-regulation on T cells in vitro and in vivo, as well as their immunoaugmenting effect in vivo. More importantly, monomeric IgD injected 6 to 24 h before a primary Ag injection also inhibits 1) the up-regulation of IgD-R on T cells induced by Ag injection alone, and 2) the generation of IgG memory, as shown in the response to a second dose of Ag injected on day 10. These results suggest that IgD-R on T cells contribute to the T-B cell interaction involved in the priming for a secondary response. The augmenting effect of oligomeric IgD and the inhibiting effect of monomeric IgD on secondary Ab responses are not observed in IgD-/- (IgD-deficient) mice, although injection of oligomeric IgD leads to IgD-R up-regulation on T cells in these mice. These results indicate that IgD presented in the form of immune complexes, most likely on the surface of B cells, is a prerequisite for the immunoaugmenting effects exerted by IgD-R+ T cells. Thus, IgD is the only physiologic ligand for IgD-R on T cells.
Apoptosis abnormalities of splenic lymphocytes in autoimmune lpr and gld mice.
Authors: Reap E A , Leslie D , Abrahams M , Eisenberg R A , Cohen P L 
Published: December 2022

Abstract
The murine gene lpr encodes an aberrant form of the apoptosis-inducing receptor Fas. The gene gld, which causes an autoimmune syndrome phenotypically identical to that caused by lpr, encodes a mutant Fas ligand. Because the lpr gene must be expressed in both T and B cells to produce autoimmune disease, it might be anticipated that apoptosis abnormalities would be present in both. Therefore, we quantitated apoptosis in T and B cells from lpr, gld, and normal mice in a short-term in vitro culture system. Freshly isolated spleen cells from normal, lpr, or gld mice showed little or no apoptosis as assessed by quantitative DNA flow cytometry. However, after overnight culture, both T and B cells showed substantial spontaneous apoptosis. Such apoptosis increased strikingly with age in normal but not in autoimmune B cells. CD23low B cells, which are prominent in lpr and gld mice, were particularly notable for high levels of programmed cell death in normal mice. The apoptosis caused by the gld defect could not be corrected by coculture with normal spleen cells. The persistence with age of low levels of B cell apoptosis in lpr and gld mice presumably reflects deficient Fas/Fas ligand interactions. The further localization of the B cell apoptosis defect to the unusual CD23low B cells, which accumulate in lpr and gld mice, adds to the evidence that these cells may be of critical importance to autoimmunity.
"Anticardiolipin" autoantibodies recognize beta 2-glycoprotein I in the absence of phospholipid. Importance of Ag density and bivalent binding.
Authors: Roubey R A , Eisenberg R A , Harper M F , Winfield J B 
Published: December 2022

Abstract
"Anticardiolipin" autoantibodies (aCL) bind to anionic phospholipids only in the presence of beta 2-glycoprotein I (beta 2GPI), a phospholipid-binding plasma protein. The exact role of beta 2GPI in the antigenic specificity of these autoantibodies is unclear, however. Experiments were performed to determine whether aCL recognize beta 2GPI in the absence of phospholipid or neo-Ags formed as a consequence of the beta 2GPI-phospholipid interaction. Although aCL+ IgG fractions did not bind to beta 2GPI alone in ELISAs that used standard polystyrene immunoassay plates, significant specific binding was detected when beta 2GPI was coated on gamma-irradiated ("high binding") polystyrene plates. This difference was associated with the greater density of beta 2GPI immobilized on the gamma-irradiated plates. Fab' fragments of patient IgG demonstrated little or no binding to immobilized beta 2GPI in ELISA, indicating a critical role for Ab bivalency. Inhibition studies of three aCL+ IgG fractions confirmed their specificity for beta 2GPI and demonstrated low affinity binding to fluid-phase beta 2GPI (Kd values of approximately 10(-5) M). aCL binding to beta 2GPI was not a result of phospholipid contamination of the assays, as determined by microphosphate assay and by lipid extraction of IgG and beta 2GPI preparations. In summary, these experiments indicate that IgG aCL are intrinsically low affinity Abs to beta 2GPI. Ab binding to beta 2GPI on a microtiter plate or anionic phospholipid membrane is dependent upon the marked increase in avidity provided by engagement of both Ag binding sites of a given IgG molecule. The data support the hypothesis that phospholipid-bound beta 2GPI is the physiologic target of aCL.
Migration of skin-homing T cells across cytokine-activated human endothelial cell layers involves interaction of the cutaneous lymphocyte-associated antigen (CLA), the very late antigen-4 (VLA-4), and the lymphocyte function-associated antigen-1 (LFA-1).
Authors: Santamaria Babi L F , Moser R , Perez Soler M T , Picker L J , Blaser K , Hauser C 
Published: December 2022

Abstract
The cutaneous lymphocyte-associated Ag (CLA) is expressed by a subset of circulating memory/effector T cells and by the vast majority of skin-infiltrating T cells. CLA is thought to target skin-associated T cells to inflammatory skin sites by interacting with endothelial cell ligand E-selectin (CD62E). We have examined adhesion molecules involved in the migration of human CLA+ and CLA- memory/effector T lymphocytes through IL-1- and TNF-alpha-activated and nonactivated HUVEC layers under static (nonflow) conditions. CLA-enriched memory/effector T lymphocytes migrated more actively across cytokine-activated HUVEC than CLA-depleted memory/effector T cells. This enhanced migration is dependent on the CLA/E-selectin interaction. mAb to very late Ag-4 (VLA-4) and vascular cell adhesion molecule-1 (VCAM-1) blocked the migration of CLA-enriched, but not of CLA-depleted, T cells across activated HUVEC. The observation that anti-VLA-4 and anti-CLA mAb did not show additional inhibition supports the concept that CLA and VLA-4 are sequentially involved in the extravasation. The fact that only CLA+ T cells were inhibited by the anti-VLA-4 mAb suggests that, in this system, CLA engagement is required for using the VLA-4/VCAM-1 pathway. Our studies demonstrate that CLA+ T cells use LFA-1/intercellular leukocyte adhesion molecule-1 (ICAM-1) for transmigration but that CLA expression is not required for the LFA-1/ICAM-1-dependent transmigration because anti-CD18/CD11a mAbs and anti-ICAM-1 mAbs were able to block T cell migration regardless of the activation state of HUVEC or the CLA expression by T cells. Taken together, our results suggest that CLA has a homing function in conducting the T cell to interact with LFA-1/ICAM-1 and/or VLA-4/VCAM-1; this results in enhanced adhesion and migration across cytokine-activated endothelial cells.
Undetectable CD40 ligand expression on T cells and low B cell responses to CD40 binding agonists in human newborns.
Authors: Durandy A , De Saint Basile G , Lisowska-Grospierre B , Gauchat J F , Forveille M , Kroczek R A , Bonnefoy J Y , Fischer A 
Published: December 2022

Abstract
IgG, IgA, and IgE production by newborn B cells is limited both in vivo and in vitro in various activation conditions, whereas IgM production is readily detectable. It has been suggested that the Ig heavy chain switch inability could be the consequence of T and B cell immaturity. As the interaction between CD40 (expressed on B cells) and its ligand CD40-L (expressed on activated T cells) triggers a key signal required for isotype switching, we studied the expression and function of these two components in normal fetuses, newborns, and infants, compared with adults. CD40-L expression was not inducible in 28 of 30 specimens of newborn cord-blood T cells following incubation with PMA and ionomycin, whereas activation markers such as CD69 were inducible. CD40-L expression was triggered by activation of T cells from infants &gt; 3 wk of age. Surprisingly, T cells from 19- to 28-wk-old fetuses also expressed CD40-L following activation. CD40-L expression on newborn T lymphocytes was induced on T cell lines generated in the presence of PHA and maintained with IL-2 following further stimulation with PMA and ionomycin. CD40-L mRNA transcripts and intracytoplasmic protein expression following activation of newborn T cells were strongly decreased, leading to undetectable protein membrane detection. These results point to a possible transcriptional down-regulation of CD40-L expression by neonatal T lymphocytes. In addition, fetal and cord-blood B cells were poorly able to switch to IgG or IgA by stimulation with CD40 agonists (Ab or soluble CD40-L) in the presence of IL-4 or IL-10 as also detected with surface IgD+ adult B cells. Both phenomena could contribute to the neonatal Ig switch inability, although distinct underlying regulatory mechanisms are probably involved, as suggested by different in vivo time courses.
Specific unresponsiveness to a retrovirally-transferred class I antigen is controlled through the helper pathway.
Authors: Fraser C C , Sykes M , Lee R S , Sachs D H , LeGuern C 
Published: December 2022

Abstract
To investigate the potential role for gene therapy in induction of tolerance to solid organ grafts, we used a murine model based on the introduction of an allogeneic MHC class I gene (H-2Kb) into hematopoietic cells of congenic animals differing only at the class I locus. The H-2Kb gene was placed into a retroviral vector under the control of regulatory sequences of the myeloproliferative sarcoma virus long terminal repeat. Transplantation of H-2Kb retrovirus-transduced autologous bone marrow into B10.AKM (Kk Ik Dq) recipients resulted in detectable levels of H-2Kb RNA and cell surface protein in lymphoid and myeloid lineages. H-2Kb expression was significant, although variable, in bone marrow Mac1+ cells, in splenic B cells, and in CD4+/CD8+ thymocytes 8 wk post-bone marrow transplantation. The recipients of the H-2Kb-transduced bone marrow showed specifically delayed rejection of B10.MBR (Kb Ik Dq) skin grafts disparate only for Kb. However, B10.MBR skin grafts were rapidly rejected when grafted simultaneously with skin grafts from B10 (Kb Ib Db) mice, a strain bearing additional third party alloantigens in association with Kb. Our experiments suggest that the hyporesponsive state induced by using the retrovirally mediated gene transfer model is characterized by the persistence of H-2Kb-specific cytolytic T cell precursors, which may be inactive because of deficient T cell help. Tolerance to Kb induced by this approach may therefore be restricted to T helper cell lineages.
Expression and function of the gamma c subunit of the IL-2, IL-4, and IL-7 receptors. Distinct interaction of gamma c in the IL-4 receptor.
Authors: He Y W , Adkins B , Furse R K , Malek T R 
Published: December 2022

Abstract
IL-2R, IL-4R, and IL-7R share a common subunit referred to as gamma c and the IL-13R has been proposed to contain gamma c as a subunit. In this report we have used two novel mAbs (3E12 and 4G3) to distinct epitopes of mouse gamma c to determine its lymphoid cell distribution and to examine whether gamma c uses similar epitopes to interact with different cytokines and cytokine receptors. FACS analysis revealed that gamma c is expressed in most lymphocytes, myeloid cells, embryonic thymocytes, and lymphoid cell lines. Results from radiolabeled ligand binding studies, biochemical analysis of ligand-receptor cross-linked complexes, and cytokine bioassays indicate that the epitope defined by mAb 4G3 closely defines the IL-7 binding region of gamma c and overlaps the IL-2 binding region of gamma c. These studies also indicate that gamma c interacts with IL-4 in the context of the IL-4R in a manner that is distinct from its role in the IL-2R and IL-7R and suggest that the 3E12 epitope defines a region of gamma c that intimately interacts with the IL-4R. The B9 plasmacytoma, which proliferates in response to IL-4 and IL-13, was shown to not express gamma c. Thus, at least in some circumstances, gamma c is dispensable for signaling via the IL-4R and is not a required subunit of the IL-13R.
Gamma delta T cell recognition of tumor Ig peptide.
Authors: Kim H T , Nelson E L , Clayberger C , Sanjanwala M , Sklar J , Krensky A M 
Published: December 2022

Abstract
Although gamma delta T cells have been postulated to act as a surveillance mechanism that eliminates transformed or otherwise damaged cells, little is known about tumor recognition by gamma delta T cells, including the Ags that are recognized and the molecules that present them. Previously, we described human gamma delta CTL that recognize the autologous B cell lymphoma. Here we report that these gamma delta CTL lyse heterologous cells transfected with the tumor Ig lambda chain gene. Furthermore, the lambda chain is recognized as processed peptide in an Id-specific manner. T cell recognition does not involve classical MHC molecules, but it could be blocked by Abs directed against the heat shock protein grp75. These findings show a specific gamma delta T cell response to a highly polymorphic Ag such as tumor Id and implicate heat shock protein as a molecule required for recognition.
Transferrin receptor induces tyrosine phosphorylation in T cells and is physically associated with the TCR zeta-chain.
Authors: Salmerón A , Borroto A , Fresno M , Crumpton M J , Ley S C , Alarcón B 
Published: December 2022

Abstract
In addition to being an iron transporter, the transferrin receptor (TfR) has been shown to play a role in T cell activation. Stimulation of the TfR with specific Abs results in T cell proliferation, IL-2 secretion, and protein kinase C activation. In this paper we have analyzed early events caused by activation of the TfR. We have found several protein substrates to be tyrosine phosphorylated upon TfR stimulation in the human Jurkat T cell line. Interestingly, the TfR induced tyrosine phosphorylation in cell lines expressing TCR but not in TCR-negative mutants. Restoration of the TCR surface expression in these mutants reestablished the ability of the TfR to induce tyrosine phosphorylation. This result suggests that activation through the TfR is functionally dependent upon the expression of the TCR. Moreover, the functional relationship of the TfR with the TCR complex is also supported by data showing that TfR stimulation resulted in the tyrosine phosphorylation of the TCR zeta-chain; conversely, stimulation of the TCR complex resulted in an increased tyrosine phosphorylation of the TfR. More importantly, the TfR is shown to associate physically with the TCR zeta-chain as well as with the zeta-binding ZAP70 tyrosine kinase. The TfR/zeta complex is expressed on the cell surface independent of the expression of the other subunits of the TCR complex. We suggest that the TfR/zeta complex is responsible for transducing the TfR-induced signals, and that it could serve to amplify signals delivered by Ag binding to the TCR.
Protein kinase C mediates activation of nuclear cAMP response element-binding protein (CREB) in B lymphocytes stimulated through surface Ig.
Authors: Xie H , Rothstein T L 
Published: December 2022

Abstract
The cAMP response element-binding protein (CREB) is generally considered to be responsive to elevation of cAMP through the activity of protein kinase A (PKA). Although it is well known that cAMP-raising agents can strongly influence B cell stimulation, the regulation of CREB has been little studied. Recently, cross-linking of surface Ig (sIg) was shown to result in trans-activation of a cAMP response element (CRE)-dependent promoter to which bound B cell CREB. In this study, we explored the mechanism underlying this unexpected linkage between sIg and CREB. We found that sIg cross-linking results in phosphorylation of CREB at Ser133. Although this phosphorylation step is mediated by PKA in pheochromocytoma cells, it depends on protein kinase C (PKC) in B lymphocytes. This conclusion is based on abrogation of sIg-induced CREB Ser133 phosphorylation by long-term phorbol-ester treatment to deplete PKC, and mimicking of sIg-induced CREB phosphorylation and CRE-dependent gene expression by short-term PKC agonism. Furthermore, CD40 ligand (CD40L) and LPS, two PKC-independent forms of B cell stimulation, failed to induce phosphorylation of CREB Ser133. These results suggest that CREB responds to specific surface-receptor signals in B cells and that this response is mediated by PKC. Interestingly, forskolin failed to induce phosphorylation of CREB Ser133 in B cells, although it did so in PC12 pheochromocytoma cells. Taken together with PKC mediation of CREB Ser133 phosphorylation in B cells, these results suggest that the dominant mode of CREB regulation is cell-type specific.
T cell subset-dependent modulation of immunity to Borrelia burgdorferi in mice.
Authors: Keane-Myers A , Nickell S P 
Published: December 2022

Abstract
The possible involvement of specific T cells in resolution of infections with Borrelia burgdorferi (Bb), the causative agent of human Lyme disease, has not been adequately studied. To investigate the potential role of T cell subsets in resistance, we have depleted mice of CD4+ and CD8+ T cell subsets in vivo by the administration of specific mAbs and have examined outcomes after infection with Bb. Our results indicate that CD4+ T cells are required for immunologic control of spirochete levels, because their depletion in both susceptible C3H/HeN and resistant BALB/c mice increased the severity of arthritis and the numbers of spirochetes found in joints and skin, as compared with Bb-infected mice treated with a control mAb. In contrast, the CD8+ T cell compartment, particularly in susceptible C3H/HeN mice, appears to promote the disease process, possibly by interfering with the generation of protective immunity, as abrogation of this subset in vivo led to a reduction in both arthritis and in spirochete levels found in joints and skin when compared with Bb-infected control mice. Our inability to establish a correlation between resistance and Bb-specific IgG Ab levels in these mice raises the possibility that Ab-independent mechanisms are important in protection. These findings suggest that the final outcome in Bb-infected hosts may be the net effect of antagonistic influences exerted by CD4+ and CD8+ T cell subsets.
Human urokinase-type plasminogen activator primes neutrophils for superoxide anion release. Possible roles of complement receptor type 3 and calcium.
Authors: Cao D , Mizukami I F , Garni-Wagner B A , Kindzelskii A L , Todd R F , Boxer L A , Petty H R 
Published: December 2022

Abstract
Urokinase-type plasminogen activator (uPA), which binds to cells via a specific receptor (uPAR), participates in pericellular proteolysis during leukocyte migration. Previous studies have indicated that uPAR is physically associated with CR3 (CD11b/CD18). To test the functional interactions of CR3 and uPAR, we have examined the ability of uPA to elicit changes in cytosolic calcium levels of normal neutrophils, neutrophils from a leukocyte adhesion deficiency (LAD) patient, and 3T3 transfectants expressing CR3, uPAR, or both. We found that calcium levels of neutrophils increased from 106 +/- 6 nM in untreated cells to 199 +/- 25 nM in the presence of uPA. In contrast, no significant change in calcium was observed when neutrophils from an leukocyte adhesion deficiency patient were examined. The uPA-dependent calcium rise was inhibited by mAb directed against either CR3 or uPAR and required intact uPA. To substantiate further these findings, we prepared transfectants expressing genes encoding uPAR, CR3, and both receptors; only cells expressing both receptors experienced a rise in intracellular calcium. Although uPA's calcium signal is insufficient to trigger superoxide production, FMLP dose-dependent superoxide production was greatly enhanced by incubating neutrophils with intact, but not fragmented, uPA. Flow cytometry experiments utilizing an FMLP analogue exclude the possibilities that urokinase binds to the FMLP receptor or up-regulates its expression. We suggest that calcium is a second messenger of uPA, that this message is mediated in a CR3-dependent fashion, and that this signal primes neutrophils for superoxide production.
The complex of FK506-binding protein 12 and FK506 inhibits calcineurin phosphatase activity and IgE activation-induced cytokine transcripts, but not exocytosis, in mouse mast cells.
Authors: Fruman D A , Bierer B E , Benes J E , Burakoff S J , Austen K F , Katz H R 
Published: December 2022

Abstract
FK506 and cyclosporin A (CsA) are immunosuppressive agents that inhibit IL-2 production by activated T cells, but only CsA inhibits IgE activation-induced cytokine transcripts in mouse IL-3-dependent, bone marrow-derived mast cells (BMMC). We previously associated the resistance of BMMC to FK506 with a deficiency in the expression of FK506 binding protein (FKBP) 12, a molecule that forms a complex with FK506 capable of inhibiting calcineurin phosphatase activity in vitro. In this report, we establish that FKBP12 mediates FK506 inhibition of both calcineurin phosphatase activity and IgE activation-induced cytokine transcripts in a Kirsten murine sarcoma virus-immortalized mast cell line that is FKBP12 deficient. Overexpression of FKBP12 by transfection enhanced the ability of FK506 to inhibit calcineurin phosphatase activity (IC50 = 2 nM), compared with cells transfected with the expression vector alone (IC50 &gt; 30 nM). The IC50 value for FK506 inhibition of IgE activation-induced transcripts for TNF-alpha decreased from 40 nM in vector control cells to 10 nM in FKBP12 transfectants. Similarly, the IC50 value for inhibition of IL-6 transcripts decreased from &gt; 1000 nM in vector control cells to 35 nM in FKBP12 transfectants. In contrast, activation-elicited release of the secretory granule mediator beta-hexosaminidase was only partially inhibited by FK506 at 1000 nM, regardless of the levels of FKBP12 expressed by the cells. Thus, FKBP12 is the dominant cytosolic protein that mediates FK506 inhibition of TNF-alpha and IL-6 transcripts.