bluuebunny/crossref_metadata_2025_split huggingface dataset:
B7.2 expressed by T cells does not induce CD28-mediated costimulatory activity but retains CTLA4 binding: implications for induction of antitumor immunity to T cell tumors.
Authors: Greenfield E A , Howard E , Paradis T , Nguyen K , Benazzo F , McLean P , Höllsberg P , Davis G , Hafler D A , Sharpe A H , Freeman G J , Kuchroo V K 
Published: December 2022

Abstract
The B7 family of costimulatory molecules provides the second signal necessary for activation of T cells. In the absence of the second signal, responding T cells become anergic. Although predominantly expressed on professional APCs, recent evidence shows that the B7 molecules are also expressed on T cells. To study the functions of B7 molecules on T cells, we transfected murine B7.1 (CD80) and B7.2 (CD86) cDNAs into the EL4 T cell thymoma cell line and examined the transfectants for their ability to costimulate T cell proliferation in vitro and to induce antitumor immunity in vivo. Here we show that although EL4-B7.1 cells costimulate T cells and induce tumor regression, EL4-B7.2 transfectants failed to costimulate T cell proliferation or induce tumor regression. To understand the cellular basis for this difference, we examined the binding of EL4-B7.1 and EL4-B7.2 to CTLA4 and CD28. Whereas EL4-B7.1 cells bound both CTLA4-Ig and CD28-Ig, EL4-B7.2 transfectants preferentially bound CTLA4-Ig, but not CD28-Ig. Similar binding data were obtained with freshly isolated murine T cells, which have been shown to constitutively express B7.2. Our data suggest, therefore, that B7.2 expressed on T cells may not costimulate but instead inhibit the T cell response by preferential binding to CTLA4.
Phosphorylation of the NC-1.1 receptor and regulation of natural cytotoxicity by protein kinase C and cyclic GMP-dependent protein kinase.
Authors: Holmgreen S P , Wang X , Clarke G R , Noltorp R S , Roberts T K , Burton R C , Robinson P J , Smart Y C 
Published: December 2022

Abstract
Natural cytotoxicity (NC) against cancer involves receptor-ligand interactions between lymphohemopoietic cells that mediate NC against tumor cells. The only candidate for a receptor on cells mediating NC is NC-1.1, identified using mAb 1C4. In this study we showed that mAb 1C4 blocked NC-1.1+ cell conjugation to WEHI-164 tumor cells, indicating that NC-1.1 is a surface protein required for cell-cell interaction. Affinity-purified NC-1.1 was a 45-kDa monomeric protein. It was a good in vitro substrate for cyclic GMP (cGMP)-dependent protein kinase (PKG) and protein kinase C (PKC) and a relatively poor substrate for cAMP-dependent protein kinase (PKA). Phosphopeptide mapping revealed one phosphopeptide phosphorylated by PKG and PKA, and two additional peptides phosphorylated by PKC. Phosphorylation by PKG or PKA abolished phosphorylation at the PKC sites, while coincubation of NC-1.1 with both PKG and PKC reduced phosphorylation of all sites. NC-1.1 was also a phosphoprotein after immunoprecipitation from intact spleen cells and its phosphorylation was increased after cell stimulation with PKC or PKG activators (phorbol esters or 8-bromo-cGMP). The possible consequences of intracellular signaling were tested in functional assays for NC. Phorbol ester activation of spleen cells increased NC, while 8-bromo-cGMP and 8-bromo-cAMP had little effect. However, coincubation with both phorbol ester and either 8-bromo-cGMP or 8-bromo-cAMP virtually abolished NC without affecting cell conjugation. These results suggest that NC-1.1 is a receptor for a ligand on certain tumor cells and reveal that key intracellular signaling pathways involving PKC, PKG, and PKA interact to effect a coordinated control of NC.
Overexpression of c-fos inhibits down-regulation of a cyclin-dependent kinase-2 inhibitor p27Kip1 in splenic B cells activated by surface Ig cross-linking.
Authors: Kobayashi K , Phuchareon J , Inada K , Tomita Y , Koizumi T , Hatano M , Miyatake S , Tokuhisa T 
Published: December 2022

Abstract
Splenic B cells activated by surface Ig (sIg) cross-linking transiently express the c-fos gene within 0.5 h and then enter into S phase of the cell cycle within 48 h. To investigate a role of c-fos in cell cycle progression, we used splenic B cells from IFN-alphabeta-inducible c-fos transgenic mice (Mx-c-fos). In the absence of IFN, the cell cycle progression of Mx-c-fos B cells stimulated with anti-IgM Ab was similar to that in control B cells. The cell cycle was arrested in G1 phase when we added IFN to the culture within 12 h after anti-IgM Ab stimulation, suggesting that overexpression of c-fos until mid-G1 phase perturbs activation of the cell cycle regulatory machinery. In control B cells, cyclin E and cdk2 were induced within 24 to 48 h after stimulation, and this induction was accompanied by down-regulation of a cdk2 inhibitor p27Kip1. As a consequence of these activation processes, cdk2 kinase activity was induced in B cells in the late G1 phase. However, kinase activity was not detected in Mx-c-fos B cells, presumably because the down-regulation of p27 was perturbed. These data suggest that c-Fos can negatively control cell cycle regulatory machinery in sIg-stimulated B cells.
Nonclassical behavior of the mouse CD1 class I-like molecule.
Authors: Teitell M , Holcombe H R , Brossay L , Hagenbaugh A , Jackson M J , Pond L , Balk S P , Terhorst C , Peterson P A , Kronenberg M 
Published: December 2022

Abstract
The mouse CD1 (mCD1) molecule is a class I-like molecule that is encoded outside of the MHC. We show here that mCD1 shares several properties with Ag-presenting class I molecules, including a requirement for beta2-microglobulin for stable cell-surface expression in T lymphocyte transfectants and thymocytes. mCD1 is also capable of binding to mouse CD8alphabeta heterodimers participating in the activation of CD8+ T cells in a manner similar to classical class I molecules. However, mCD1 surface expression is not decreased at high temperatures in cells that lack the transporter associated with Ag processing (TAP), including both RMA-S and Drosophila melanogaster cells. The data indicate that mCD1 does not require TAP to be expressed in a stable fashion at the cell surface. We speculate that the ability of mCD1 to reach the cell surface in transporter-deficient cells may reflect its ability to present a distinct set of ligands. The properties of mCD1 described here can account, in part, for the selection of the diverse populations of T cells that are known to be mCD1 reactive.
Anti-human class I MHC antibodies induce apoptosis by a pathway that is distinct from the Fas antigen-mediated pathway.
Authors: Woodle E S , Smith D M , Bluestone J A , Kirkman W M , Green D R , Skowronski E W 
Published: December 2022

Abstract
5H7, an anti-human class I MHC mAb that recognizes a monomorphic determinant of the alpha3 domain, profoundly inhibits T lymphocyte activation. The present study was designed to determine the role of programmed cell death in 5H7-mediated immune suppression. Incubation of PBMC with 5H7 mAb induced a marked reduction in viable cell recovery (VCR) of T cells (&lt;10% VCR), NK cells (&lt;1% VCR), and B cells (&lt;1% VCR). In addition, 5H7 inhibited proliferation and VCR of JY, DBS-521, and BevD tumor lines as well as cells transfected with HLA-B27. Morphologic changes characteristic of apoptosis were induced by 5H7, including cell membrane blebbing, cytoplasmic vacuolization, condensation of nuclear chromatin, and nuclear fragmentation. Furthermore, DNA fragmentation was demonstrated in 5H7-treated PBMC using a TdT-mediated end-labeling (TUNEL) technique. 5H7, but not anti-Fas mAb, induced apoptosis of cell lines derived from patients with Niemann-Pick disease that lack acidic sphingomyelinase activity. In addition, induction of cell death by 5H7 was not inhibited by IL-1beta-converting enzyme (ICE) inhibitors under conditions that fully suppressed Fas-mediated apoptosis. These findings suggest that signal transduction through "classical" human class I MHC molecules induces apoptosis by a Fas-independent pathway that does not require acidic sphingomyelinase, is independent of ICE protease, and may represent a unique pathway of cell death in human lymphocytes.
Structural consequences of humanizing an antibody.
Authors: Holmes M A , Foote J 
Published: December 2022

Abstract
We have determined the crystal structure of the Fv fragment of a humanized anti-hen eggwhite lysozyme Ab (HuLys). This molecule is a composite of known structures: complementarity-determining regions (CDRs) were from the mouse anti-lysozyme Ab D1.3, heavy chain framework regions were from the human myeloma protein NEW, and the light chain framework regions were consensus sequences similar to the Bence Jones protein REI. HuLys crystallized in space group P4(3)2(1)2, with two Fv molecules in the crystallographic asymmetric unit. The structure was solved by molecular replacement, using a composite of the parent structures as a search model. The resolution of the structure was 2.87 A, with an R factor of 22%. There were several unanticipated structural similarities and differences between HuLys and the mouse and human structures. The framework regions of HuLys were as close or closer in conformation to D1.3 than to the NEW or REI protein, despite overwhelming sequence identity with the human framework regions. The effect was most pronounced at the CDR-framework junction, showing that the CDRs can induce structural changes in framework residues, having the net effect in HuLys of reconforming the framework into a conformation more like D1.3. In the combining site, the grafted CDRs retained conformational equilibria seen in D1.3, demonstrating that humanizing can be applied to Abs that bind Ags through isomeric equilibrium or induced fit mechanisms. In addition, HuLys showed systematic differences from D1.3 that resembled domain rotations reported for other Abs. However, the V(H)-V(L) interface itself was unaffected, and the apparent movement was actually caused by rearrangements distant from this surface.
Delineation of the amino acid residues involved in transcytosis and catabolism of mouse IgG1.
Authors: Medesan C , Matesoi D , Radu C , Ghetie V , Ward E S 
Published: December 2022

Abstract
The MHC class I-related receptor, FcRn, is involved in both the transcytosis of serum gamma-globulins (IgGs) and in regulating their serum persistence. The interaction site of FcRn on the Fc region of rodent IgG has been mapped to residues at the CH2-CH3 domain interface using site-directed mutagenesis and x-ray crystallographic analyses. In the current study, the role of individual residues (H310, H433, and N434) at this interface in mediating the Fc-FcRn interaction has been investigated using recombinant, mutated Fc hinge fragments derived from mouse IgG1. In addition, two highly conserved Fc histidines (H435 and H436) have been mutated to alanine, and the resulting mutated Fc hinge fragments were analyzed in both transcytosis and pharmacokinetic studies in mice and in competition binding assays using recombinant, soluble FcRn. The analyses indicate that mutation of H310, H435, and, to a lesser extent, H436 to alanine results in reduced activity of the Fc hinge fragments in both in vivo and in vitro assays. Thus, in addition to the previously defined role of 1253 in the FcRn-IgG interaction, these histidines play a key role in mediating the functions conducted by this Fc receptor. The effects of these mutations on binding of Fc hinge fragments to staphylococcal protein A have also been analyzed and demonstrate a partial, but not complete, overlap of the FcRn and staphylococcal protein A interaction sites on mouse IgG1.
Prominence of beta 2-microglobulin, class I heavy chain conformation, and tapasin in the interactions of class I heavy chain with calreticulin and the transporter associated with antigen processing.
Authors: Solheim J C , Harris M R , Kindle C S , Hansen T H 
Published: December 2022

Abstract
Newly synthesized class I heavy (H) chain/beta 2m heterodimers awaiting peptides in the endoplasmic reticulum are associated with the transporter associated with Ag processing (TAP). We present evidence here that calreticulin, but not calnexin, displays steady state association with class I/TAP complexes. To separate the ability of beta 2m to bind with TAP and calreticulin from that of H chain, we studied human cell lines that lack expression of beta 2m or H chain. Little if any H chain was detected in association with TAP and calreticulin in the beta 2m- cell line Daudi. By contrast, high levels of beta 2m are found with TAP and calreticulin in the H chain-deficient cell line LCL 721.221, even after preclearance of the trace amount of class IB protein expressed by this cell line. Thus, beta 2m appears to bind TAP in the absence of H chain, providing an elegant mechanism to retain beta 2m in the endoplasmic reticulum at the site of peptide loading. To investigate whether other molecules participate in the binding of beta 2m and H chain to TAP and calreticulin, we analyzed the deletion mutant cell line LCL 721.220, which lacks tapasin. In 721.220, TAP and calreticulin are not associated with each other. Also, in these cells, H chain/beta 2m are not associated with TAP, but H chain and a low level of beta 2m are associated with calreticulin. These results suggest that tapasin is an obligatory mediator of the assemblage of calreticulin/H chain/beta 2m with TAP.
Substance P-induced IL-12 production by murine macrophages.
Authors: Kincy-Cain T , Bost K L 
Published: December 2022

Abstract
Previous investigations in our laboratory have suggested that substance P (NK-1) receptor expression by macrophages contributes to the resistance against the intracellular bacterial pathogen, Salmonella. To investigate possible mechanisms for such resistance, macrophages were cultured with varying concentrations of a substance P agonist to investigate the ability of this neuropeptide to augment IL-12 expression. The substance P agonist was a potent inducer of both IL-12p35 and IL-12p40 mRNA expression in cultured macrophages. The kinetics of this response were maximal within 6 h and could be observed with concentrations of substance P agonist as low as 0.1 nM. The nonpeptide, substance P receptor antagonist, CP96-345, significantly blocked agonist-induced IL-12 mRNA expression, further demonstrating that this effect was mediated through an NK-1 receptor. Substance P agonist alone could stimulate substantial secretion of IL-12p40, but not IL-12p70, by cultured macrophages. Thus, the substance P agonist had the ability to augment IL-12p35 and IL-12p40 mRNA expression, but not to increase IL-12p70 secretion. Like IFN-gamma, we found that substance P could combine with LPS to significantly augment the secretion of bioactive IL-12p70. The costimulatory effects of substance P agonist plus LPS on IL-12 mRNA expression were additive; however, this combination resulted in synergistic secretion of IL-12p70 by macrophages. Together, these results demonstrate the ability of NK-1 receptors to signal IL-12 production by macrophages and suggest mechanisms for substance P-induced modulation of cellular immunity.
IL-4 expression at the onset of islet inflammation predicts nondestructive insulitis in nonobese diabetic mice.
Authors: Fox C J , Danska J S 
Published: December 2022

Abstract
In nonobese diabetic mice, autoimmune diabetes progresses in an age-linked and gender-dependent manner. Insulitis begins in male and female mice at approximately 1 mo of age; however, 70 to 90% of females, but only 10 to 20% of males, become diabetic by 6 mo. Multiple studies propose that proinflammatory Th1 and immunomodulatory Th2 cytokines impact diabetes pathogenesis, but the role of these cytokines in spontaneous diabetes progression is not yet clear. We used quantitative reverse-transcriptase-coupled PCR to analyze expression of cytokines and APC costimulatory molecules in the islets of 20- to 180-day-old male and female nonobese diabetic littermates, and identified three stages in diabetes progression. At 1 to 2 mo of age, islet-infiltrating T cells displayed a Th1 cytokine bias in females, and a Th2 cytokine bias in males. In females, stage II (2-3 mo of age) was characterized by an increase in islet-infiltrating T cells, APC, and Th1 cytokines, whereas male infiltrates did not increase in size, and Th1 cytokine expression continued to decline during this interval. Islet infiltration reached a plateau (stage III) in 3- to 4-mo-old females, months before overt diabetes onset. Our data imply that Th cytokine expression in early insulitis exerts substantial impact on beta cell destruction and overt diabetes. A clinical implication of our results is that young individuals in the early stages of insulitis are ideal candidates for therapeutic intervention to minimize beta cell destruction and morbidity.
Modulation of the immune response in multiple sclerosis: production of monoclonal antibodies specific to HLA/myelin basic protein.
Authors: Puri J , Arnon R , Gurevich E , Teitelbaum D 
Published: December 2022

Abstract
Monoclonal Abs to the complex formed between human MHC class II molecules (DR7 and DRw11) and myelin basic protein (MBP) were produced. The specificity of these Abs was established by both FACS analysis and complement-mediated cytotoxicity of MBP- or OVA-pulsed human APC of the same or of different DR restriction. These Abs bound to and lysed only MBP-pulsed human APC of the same DR restriction (DR7 or DRw11) but not to APC of different DR restriction or pulsed with a different Ag (OVA). The physiologic role of these Abs was further investigated. They blocked the in vitro proliferative response to MBP-specific T cell clones isolated from multiple sclerosis patients in an antigen-specific and DR-restricted manner. However, the Abs did not affect the response of MBP-specific T cell clones of other DR restriction nor did they interfere with the response to other Ags (purified protein derivative or copolymer 1) presented on APC with the same DR restriction. These Abs may be useful for treating multiple sclerosis in which reactivity to MBP is implicated. Moreover, this approach may be extended to other autoantigens and their counterpart autoimmune diseases.
Membrane IgM-induced tyrosine phosphorylation of CD19 requires a CD19 domain that mediates association with components of the B cell antigen receptor complex.
Authors: Carter R H , Doody G M , Bolen J B , Fearon D T 
Published: December 2022

Abstract
CD19 enhances membrane IgM (mIgM) signaling and is required for B lymphocyte responses to T-dependent Ags. CD19 is tyrosine phosphorylated when mIgM is ligated and binds SH2 domain-containing signaling proteins. We suggest that the basis for phosphorylation is the association of CD19 with Syk and other components of the mIgM complex. IgM, CD22, Ig-alpha, Ig-beta, and Syk were coimmunoprecipitated with CD19 from detergent lysates of B lymphocytes. The association was maintained with a chimeric form of CD19 containing only the transmembrane domain and the membrane proximal 17 amino acids of the cytoplasmic domain encoded by exon 6. This sequence is sufficient to mediate the association, as a synthetic peptide of the exon 6-encoded region adsorbs IgM and Syk. Deletion of the juxtamembrane 17 amino acids of the cytoplasmic domain encoded by CD19 exon 6 abolishes association of CD19 with the mIgM complex. Deletion of these amino acids, which contain no tyrosines, also reduces mIgM-induced tyrosine phosphorylation of the remainder of the CD19 cytoplasmic domain. Coligating this mutant CD19 to mIgM restores phosphorylation. Thus, a discrete region of the cytoplasmic domain regulates the tyrosine phosphorylation of CD19 in the activation of B cells by mIgM.
Altered expression of Ly49 inhibitory receptors on natural killer cells from MHC class I-deficient mice.
Authors: Salcedo M , Diehl A D , Olsson-Alheim M Y , Sundbäck J , Van Kaer L , Kärre K , Ljunggren H G 
Published: December 2022

Abstract
MHC class I molecules in the host affect the specificity of NK cells. Previous work has suggested that this specificity is conferred by the expression of products encoded by the Ly49 gene family. This gene family encodes receptors that upon specific recognition of MHC class I ligands mediate an inhibitory signal that prevents killing by NK cells. The pattern of expression of the Ly49 MHC class I binding inhibitory receptors on NK cells is thought to be adapted to the host to ensure the generation of a self-tolerant, yet functional, NK cell repertoire. In the present study we have examined the expression of inhibitory receptors (Ly49A, Ly49C, and Ly49G2) on NK1.1+ cells from B6 (H-2b) and D8 (B6 mice transgenic for H-2Dd) mice as well as corresponding TAP1 -/-, beta2m -/-, and TAP1/beta2m -/- mutants of these mice. We demonstrate that receptor expression on NK1.1+ cells can be specifically modulated by host MHC class I molecules in at least two different ways: alteration of numbers of cells expressing a given receptor and modulation of the levels of expression of a given receptor at the cell surface. The degree of this modulation varies significantly among the various receptors studied and may depend upon the nature of their MHC class I ligands. The results are discussed in relation to the influence of MHC class I molecules on the development of an NK cell repertoire.
Regulation of telomerase RNA template expression in human T lymphocyte development and activation.
Authors: Weng N , Levine B L , June C H , Hodes R J 
Published: December 2022

Abstract
Telomeres are unique DNA-protein complexes at the terminals of chromosomes that appear to play a critical role in protecting chromosomal integrity and in maintaining cellular replicative potential. Telomerase is a ribonuclear protein that is capable of elongating telomeres by the addition of telomeric hexanucleotide repeats and therefore contributing to the capacity for cell replication. Telomerase activity is expressed in human germline cells and malignant cells, and it has recently been demonstrated that telomerase activity is highly regulated in normal lymphocytes at specific stages of development and activation. However, these studies have not elucidated whether telomerase activity is regulated at the level of specific gene expression or whether the regulation of telomerase RNA template (hTR) and/or protein components contributes to the regulation of telomerase activity in normal somatic cells. To characterize at a molecular level the regulation of telomerase expression in human T lymphocytes, we analyzed the expression of hTR during lineage development and after in vitro activation. It was found that hTR is expressed in subsets of thymocytes with strong telomerase activity at levels that are consistently higher (1.5 times; p &lt; 0.01) than those found in peripheral blood resting T cells. In addition, hTR is up-regulated two- to fivefold in peripheral blood naive and memory CD4+ T cells after in vitro activation with anti-CD3 plus anti-CD28. These results establish that hTR expression is regulated in normal human T cells during lineage development and after activation, and indicate that regulation of hTR expression may contribute to the regulation of telomerase activity in normal lymphoid cells.