bluuebunny/crossref_metadata_2025 huggingface dataset:
Activated human NK cells can stimulate resting B cells to secrete immunoglobulin.
Authors: Gray J D , Horwitz D A
Published: December 2022

In addition to their cytotoxic function, NK cells can either suppress or enhance Ab production. Upon activation, NK cells generally amplify Ig secretion by activated B cells. We now report that activated NK cells prepared from human peripheral blood can induce resting B cells to produce IgM and IgG. This was demonstrated by adding IL-2 or pokeweed mitogen to purified NK cells and B cells. The addition of IL-2-activated NK cells to B cells also had this effect. The responding B cells did not require activation. Moreover, following fractionation of B cells on Percoll gradients, responsive B cells were found in the high density as well as the low density fractions. The NK cell stimulatory effect was a two-step process. The first step induced B cells to respond to soluble mediators and was mediated by unstimulated NK cells, but not CD4 nor CD8 T cells. Physical contact between NK cells and B cells was required, and mAbs to CD11a and CD54 blocked this interaction. The second step was the production of as yet unidentified cytokine(s) by activated NK cells. These direct T cell-independent stimulatory effects of NK cells on B cells may be important in autoimmune and other chronic inflammatory diseases in which the suppressive effects of NK cells may be blocked.
Up-regulation of inducible cyclooxygenase gene expression by platelet-activating factor in activated rat alveolar macrophages.
Authors: Thivierge M , Rola-Pleszczynski M
Published: December 2022

Platelet-activating factor (PAF) can stimulate alveolar macrophages (AM) to produce IL-6 through a PG-dependent process. In this study, the modulation by PAF of the expression of COX-2, the inducible isoform of PG synthase, was investigated. Expression of COX-2 mRNA was increased in rat AM within 2 h after treatment with either of the bacterial products LPS or muramyl dipeptide (MDP) alone. Although PAF had no effect by itself, stimulation of AM with a combination of PAF (10(-10) to 10(-8) M) and LPS or MDP resulted in a synergistic, three- to fivefold increase in levels of COX-2 mRNA. No significant change was observed in the mRNA expression of the constitutive isoform, COX-1. The antagonist WEB 2170 blocked the action of PAF, whereas lyso-PAF was inactive on the COX-2 gene expression. The effect of PAF was rapid, being evident by 30 to 60 min of stimulation and was accompanied by enhanced production of PGE2. Two relatively selective inhibitors of COX-2 abolished the PAF-dependent increase in PGE2 production. Moreover, inhibition of transcription with actinomycin D completely abrogated the effect of PAF on both COX-2 mRNA and PGE2 production. These results suggest that COX-2 expression can be regulated at the transcriptional level by PAF, in synergy with bacterial products. PAF-dependent up-regulation of COX-2 expression may constitute a novel element in the interrelationship between PAF and prostanoids in the context of allergic, inflammatory, and immune processes.
Neutralizing recombinant human antibodies to a conformational V2- and CD4-binding site-sensitive epitope of HIV-1 gp120 isolated by using an epitope-masking procedure.
Authors: Ditzel H J , Binley J M , Moore J P , Sodroski J , Sullivan N , Sawyer L S , Hendry R M , Yang W P , Barbas C F , Burton D R
Published: December 2022

As part of the goal of assembling a mixture of neutralizing human mAbs for possible prophylaxis and therapy of HIV-1 disease, we describe a strategy by which neutralizing human Abs to a weakly immunogenic epitope can be accessed. From a phage display library derived from an asymptomatic HIV-1 seropositive donor, a panel of recombinant Fabs against the CD4 binding site (CD4bs) of gp120 was retrieved by affinity selection using recombinant gp120 (strain LAI). Two Fabs corresponding to the dominant clones were used to mask the CD4bs epitope(s) before repeating the selection procedure. Four Fabs were then retrieved that had novel heavy chain sequences. Three recognized a novel epitope distinct from that recognized by conventional CD4bs Abs and were defined by the following criteria: 1) second V region (V2 region) dependence indicated by sensitivity to amino acid changes in the V2 loop and by competition with murine anti-V2 mAbs; 2) CD4bs dependence indicated by sensitivity to amino acid changes usually associated with CD4 binding and by inhibition of Fab binding to gp120 by soluble CD4; this dependence seemed to arise via conformational changes rather than by direct binding, as CD4bs Abs enhanced binding of two of the novel Fabs and, in a reversal of the competition format, the novel Fabs did not inhibit soluble CD4 binding to gp120; and 3) equivalent binding to glycosylated and deglycosylated gp120 and significant, although much reduced, binding to denatured gp120 in contrast with CD4bs Abs, which do not bind to deglycosylated or denatured gp120. One of the novel Fabs efficiently neutralized the MN and LAI strains of HIV-1. These results indicate the presence of a novel neutralizing conformational epitope on gp120 sensitive to the V2 loop and the CD4bs and further highlight the conformational flexibility of gp120. The strategy of masking highly immunogenic epitopes with Abs to rescue a broader range of specific Abs from combinatorial libraries should be widely applicable.
Growth hormone is a human macrophage activating factor. Priming of human monocytes for enhanced release of H2O2.
Authors: Warwick-Davies J , Lowrie D B , Cole P J
Published: December 2022

Although many effects of growth hormone (GH) and related factors upon the immune system have been demonstrated, few studies have examined the capacity of these factors to modulate human monocyte function in vitro. Assaying a range of mediators, only GH and prolactin (PRL), at 0.3 to 1.0 micrograms/ml, and growth hormone-releasing hormone (GRH) at very high doses, primed monocytes for enhanced hydrogen-peroxide production (H2O2) in response to PMA. GH-induced priming was not caused by endotoxin, nor by production of lymphokines such as IFN-gamma. Exogenous insulin-like growth factor-I (IGF-I), alone or in combination with GH, was without effect, making it unlikely that GH mediates its effects on monocytes via an autocrine/paracrine action of IGF-I. Monocytes specifically bound radiolabeled GH and contained mRNA for the GH receptor and, in some donors, the PRL receptor. Therefore, GH probably exerts its effects as a human macrophage-activating factor through either GH or PRL receptors, without requiring production of IGF-I.
Engagement of the vitronectin receptor (alpha V beta 3) on murine T cells stimulates tyrosine phosphorylation of a 115-kDa protein.
Authors: Brando C , Shevach E M
Published: December 2022

The murine vitronectin receptor (VNR, alpha V beta 3) is expressed on T cell hybridomas expressing both the alpha beta and the gamma delta TCR as well as on TCR-alpha beta cells activated for prolonged periods of time by mitogens or alloantigens. The VNR functions as a costimulatory molecule for the activation of a subset of gamma delta T cells that express the V gamma 1.1 C gamma 4 V delta 6 TCR and that may recognize a ubiquitously expressed autoantigen. To characterize further some of the signal transduction parameters observed after engagement of the VNR in stimulated T lymphocytes, we have examined the effect of ligation of the VNR by RGDS-containing proteins on the pattern of protein phosphorylation. We demonstrate the appearance of a 115-kDa, tyrosine-phosphorylated protein (pp115) after engagement of the VNR with its ligand, RGDS. pp115 was shown to be immunologically distinct from focal adhesion kinase, did not possess inherent kinase activity, and may represent an as yet unidentified substrate in the integrin signal transduction pathway. Although induction of pp115 was independent of TCR expression, because it was seen in the TG40 hybridoma, which expresses neither the alpha beta nor the gamma delta TCR, pp115 could also be induced by cross-linking of the TCR in a murine TCR gamma delta hybridoma in the absence of any extracellular matrix proteins. This result raises the possibility that induction of pp115 is a common biochemical step in signal transduction by both the TCR and the VNR.
A monoclonal autoantibody that promotes central nervous system remyelination in a model of multiple sclerosis is a natural autoantibody encoded by germline immunoglobulin genes.
Authors: Miller D J , Rodriguez M
Published: December 2022

Antibodies directed against self-Ags are frequently considered detrimental, and have been shown to play a pathogenic role in certain autoimmune diseases. However, the presence of autoreactive Abs in normal individuals suggests that some autoantibodies could participate in normal physiology. Our previous studies demonstrated that monoclonal autoantibodies SCH94.03 and SCH94.32, generated from the splenocytes of uninfected SJL/J mice injected with normal homogenized spinal cord, promote central nervous system remyelination when passively transferred into syngeneic mice chronically infected with Theiler's murine encephalomyelitis virus, an established experimental model of multiple sclerosis. In this study we show that these two monoclonal autoantibodies are identical, and have phenotypic characteristics of natural autoantibodies. By using a solid phase assay system, SCH94.03 and SCH94.32 showed reactivity toward several protein Ags and chemical haptens, with prominent reactivity toward spectrin, (4-hydroxy-3-nitrophenyl)acetyl, and fluorescein. Sequence analysis showed that both SCH94.03 and SCH94.32 were encoded by identical germline Ig light chain V kappa 10/J kappa 1 and heavy chain V23/DFL16.1/JH2 genes, with no definitive somatic mutations. These results indicate that a natural autoantibody participates in a beneficial physiologic response to central nervous system injury.
Three functional soluble forms of the human apoptosis-inducing Fas molecule are produced by alternative splicing.
Authors: Cascino I , Fiucci G , Papoff G , Ruberti G
Published: December 2022

Fas/Apo-1 molecule is an apoptosis-signaling cell surface Ag belonging to the TNFR family. To investigate the possibility that soluble forms of the Fas receptor are expressed in human cells, we analyzed Fas mRNA transcripts obtained from activated peripheral mononuclear cells of healthy donors and from human tumor cell lines. We identified and characterized three human mRNA Fas variants: FasTMDel, FasDel2, and FasDel3. To determine whether the three transcripts were derived by alternative splicing, the Fas genomic intron/exon organization of the regions surrounding the deleted sequences was analyzed in Fas clones isolated from a human genomic library. Expression of the transcripts was studied in COS cells transiently transfected with the FasTMDel, FasDel2, and FasDel3 cDNAs. Immunocytochemical and in vitro apoptosis inhibition studies suggest that the transcripts are expressed as soluble Fas proteins that may play a functional role in the regulation of apoptosis.
Recall of long-lived immunity to Mycobacterium tuberculosis infection in mice.
Authors: Andersen P , Andersen A B , Sørensen A L , Nagai S
Published: December 2022

Our study investigates the recall of immunity in the mouse model of memory immunity to tuberculosis infection. The results provide evidence that recall of immunity is expressed as an accelerated accumulation of potent effector cells in the infected target organs. These effector cells were recruited from the resting pool of memory cells and were immediately triggered to exert their effector functions, leading to a massive release of Th1 cytokines detectable both in splenic extracts and in the serum within the first 24 h of infection. During a primary infection, in contrast, a 14-day delay was observed before significant cytokine levels were reached. After the initial effector phase, the cells blasted and entered into clonal expansion, resulting in a rapid increase in the total number of CD4 CD45RBlow cells in the spleen. The recall of memory immunity was highly efficient and controlled an infectious challenge within the first week. The molecules recognized by the memory effector subset were the proteins secreted from Mycobacterium tuberculosis during growth. By separating the CD4 population into CD45RBhigh and CD45RBlow subsets, the memory effector cells were demonstrated to reside predominantly in the activated population of CD45RBlow CD44high LFA-1high L-selectinlow cells. The key antigenic targets recognized by these cells were identified as Ag85B and a secreted 6-kDa protein (ESAT-6) that elicited the release of exceedingly high levels of IFN-gamma. ESAT-6 was biochemically purified, characterized, and the gene encoding the protein was cloned.
An adenovirus type 5 early region 1B-encoded CTL epitope-mediating tumor eradication by CTL clones is down-modulated by an activated ras oncogene.
Authors: Toes R E , Offringa R , Blom R J , Brandt R M , van der Eb A J , Melief C J , Kast W M
Published: December 2022

Mouse embryo cells (C57BL/6, H-2b) transformed by the E1A and E1B genes of adenovirus type 5 (Ad5E1 MEC) are highly immunogenic. Previously, CTL were cloned from mice immunized with Ad5E1 MEC. These CTL clones were capable of tumor eradication in nude mice, and were directed against the Ad5E1A-encoded decapeptide SGPSNTPPEI, presented by the H-2Db MHC molecule. We have now generated Ad5E1 MEC containing a mutated Ad5E1A-encoded epitope. The mutant Ad5E1 MEC induce a strong CTL response when injected into immunocompetent mice. CTL clones generated against mutant Ad5E1-transformed tumor cells recognize an Ad5E1B-encoded epitope (VNIRNCCYI) in the context of H-2Db. Because this epitope is also present on wild-type Ad5E1 MEC, it is concluded that Ad5E1-transformed tumor cells express at least two CTL epitopes. Interestingly, the lysis of Ad5E1 MEC by the Ad5E1B-specific, but not by the Ad5E1A-specific, CTL clones was strongly diminished by the action of the activated ras oncogene. CTL directed against the Ad5E1B-encoded epitope were, like Ad5E1A-specific CTL, able to eradicate large established Ad5E1-induced tumors in B6 nude mice, demonstrating that CTL activity directed against different CTL epitopes expressed by the same tumor can be exploited for immunotherapy of cancer.
Nonopsonic phagocytosis of Pseudomonas aeruginosa requires facilitated transport of D-glucose by macrophages.
Authors: Barghouthi S , Everett K D , Speert D P
Published: December 2022

Pseudomonas aeruginosa is the predominant respiratory tract pathogen in patients with cystic fibrosis (CF), and its resistance to phagocytosis may contribute to its virulence. P. aeruginosa ingestion by macrophages occurs only in the presence of D-glucose or D-mannose, sugars present in low concentrations in the endobronchial space. Here we show that only isolates of P. aeruginosa and not other bacterial species were ingested by murine macrophages in a glucose-dependent manner. Glucose transport inhibitors blocked both [3H]-2-deoxy-glucose (2dG) uptake and phagocytosis of P. aeruginosa. P. aeruginosa pretreated with 2dG or 5-thio-D-glucose (5TG) was efficiently ingested. Macrophages pretreated with 2dG or 5TG were able to bind but unable to ingest P. aeruginosa in the presence of glucose; however, they efficiently ingested zymosan or IgG-coated sheep erythrocytes. Macrophages produced lactate only from glucose or mannose. The facilitative glucose transporter GLUT1 mRNA transcript was detected by PCR in preparations from purified macrophages. The nucleotide sequence of the PCR product was identical to that published for murine GLUT1. GLUT1 protein was detected with anti-GLUT1-peptide polyclonal Abs. We conclude that glucose exerts its effect on the macrophage, not on the bacterium, in the glucose-dependent nonopsonic phagocytosis of P. aeruginosa and that glucose transport via GLUT1 by the macrophages is required to trigger ingestion. The unique glucose dependency for phagocytosis of P. aeruginosa by macrophages may contribute to the pathogenicity of this bacterial species in CF patients.
CD8 T lymphocytes specific for the secreted p60 antigen protect against Listeria monocytogenes infection.
Authors: Harty J T , Pamer E G
Published: December 2022

The ability of Listeria monocytogenes to gain access to the cytoplasm of infected cells results in the processing and presentation of bacterial Ags through the MHC class I pathway. As a result, CD8 T cells are the most effective mediators of acquired immunity in the mouse model of L. monocytogenes infection. CD8 T cells specific for a single nonamer epitope derived from the secreted virulence factor listeriolysin O (LLO) can protect H-2d mice against lethal infection. Bacteria lacking LLO are avirulent and do not elicit protective immunity in mice. Thus, the failure of LLO minus L. monocytogenes to elicit protective immunity could be caused either by their inability to enter the cytoplasm or to the lack of LLO-derived peptide epitopes. In this report we provide evidence that H-2d restricted CD8 T cells with specificity for another L. monocytogenes protein, the secreted p60 molecule, can protect against infection. Our studies further demonstrate that LLO-dependent induction of protective immunity results from access of the bacterium to the cytoplasm. In addition, these studies provide support for the hypothesis that secreted bacterial proteins are the most important targets for protective CD8 T cell-mediated immunity.
Suppression of TNF-alpha mRNA expression in LPS-primed macrophages occurs at the level of nuclear factor-kappa B activation, but not at the level of protein kinase C or CD14 expression.
Authors: Takasuka N , Matsuura K , Yamamoto S , Akagawa K S
Published: December 2022

Previously, we reported that preexposure of proteose peptone-elicited murine peritoneal exudate macrophages (P-PEM) to a low dose of LPS suppressed the expression of TNF-alpha mRNA, but not of IL-1 beta mRNA, induced by a second round of LPS exposure. To elucidate the mechanisms underlying this hyporesponsiveness to LPS, we focused on two molecules: nuclear factor (NF)-kappa B and CD14. Activation of NF-kappa B induced by a second round of LPS was suppressed in LPS-primed P-PEM much like the suppression of TNF-alpha mRNA expression. However, protein kinase C (PKC), a candidate as an activator of NF-kappa B, was not desensitized by LPS priming. LPS-induced TNF-alpha production was not affected by depletion of PKC, and LPS could not induce translocation of PKC. CD14 expression showed no significant difference between control and primed P-PEM. In contrast with J774.1 cells and thioglycolate medium-elicited macrophages (T-PEM), P-PEM exhibited serum-independent TNF-alpha production, and a polyclonal Ab to murine CD14 had no inhibitory effect on the LPS-induced TNF-alpha production by P-PEM. These results suggest that priming by LPS causes blockage at an early step, at least before the activation of NF-kappa B, in the LPS signal transduction pathway, but not at the expression of CD14. Our results also suggest that, in P-PEM, in contrast to J774.1 cells and T-PEM, neither PKC nor CD14 is involved in the LPS-induced activation and suppression of TNF-alpha gene expression.
Progesterone favors the development of human T helper cells producing Th2-type cytokines and promotes both IL-4 production and membrane CD30 expression in established Th1 cell clones.
Authors: Piccinni M P , Giudizi M G , Biagiotti R , Beloni L , Giannarini L , Sampognaro S , Parronchi P , Manetti R , Annunziato F , Livi C
Published: December 2022

The effect of progesterone (P) on the cytokine production profile of Ag-specific human CD4+ T cell lines and clones was investigated. T cell lines specific for purified protein derivative or streptokinase (SK) derived in the presence of P exhibited significant increased ability to produce IL-5 in comparison with T cell lines derived in the absence of P. Moreover, IL-4 was significantly increased in SK-specific T cell lines derived in the presence of P in comparison with SK-specific T cell lines derived in the absence of this hormone. In addition, SK-specific T cell lines generated in the presence of P developed into T cell clones showing a Th0-, instead of Th1-like, cytokine profile. Furthermore, SK-specific T cell clones with an established Th1 profile of cytokine secretion did express mRNA for, and produced detectable amounts of, IL-4 when stimulated with P in combination with insoluble anti-CD3 mAb. Combined stimulation with P and insoluble anti-CD3 mAb also enabled Th1 clones to express CD30 on their surface membrane. These results indicate that P can favor the development of Th cells producing Th2-type cytokines and is an inducer of both transient IL-4 production and CD30 expression in established Th1 cells. Thus, P production at the placental level may be responsible, at least in part, for increased production of Th2-type cytokines which have been implied in fetal allograft survival and maintenance of successful pregnancy.
Processing of exogenous heat-aggregated (denatured) and particulate (native) hepatitis B surface antigen for class I-restricted epitope presentation.
Authors: Schirmbeck R , Böhm W , Melber K , Reimann J
Published: December 2022

Many cell types efficiently present an epitope of the hepatitis B surface Ag (HBsAg) to murine class I-restricted CTL following an in vitro pulse with native 22-nm HBsAg particles. Processing of exogenous HBsAg particles required its cytochalasin B-insensitive uptake and acid proteolysis in an endocytic compartment, was insensitive to brefeldin A and cycloheximide, and did not involve regurgitation of antigenic peptides. In contrast, after an in vitro pulse of cells with exogenous, heat-denatured 1-micron HBsAg aggregates, only macrophages (but not other cell types tested) presented the Ld-restricted HBsAg epitope efficiently to CTL. Processing of exogenous HBsAg aggregates required its cytochalasin B-sensitive uptake, was insensitive to brefeldin A, and involved regurgitation of antigenic peptides. Processing of the two different, exogenous HBsAg preparations for class I-restricted epitope presentation thus involved alternative pathways: an "endocytic pathway" for native 22-nm particles, and a "phagocytic pathway" for denatured 1-microns aggregates. Both HBsAg preparations displayed different immunogenicity for class I-restricted CTL in vivo when delivered without adjuvants: native HBsAg particles were of high immunogenicity, and denatured HBsAg aggregates were of low immunogenicity. Class I-restricted CTL are thus primed in vivo after "endocytic processing" of native HBsAg particles as well as "phagocytic processing" of denatured HBsAg aggregates.
Constitutive production of IL-2 by human carcinoma cells, expression of IL-2 receptor, and tumor cell growth.
Authors: Lin W C , Yasumura S , Suminami Y , Sung M W , Nagashima S , Stanson J , Whiteside T L
Published: December 2022

Human carcinomas spontaneously express abundant IL-2R beta but little IL-2R alpha on the cell surface, contain mRNA for IL-2R beta- and IL-2R alpha-chains, and may be inhibited in growth by exogenous IL-2. To study the relationship between IL-2R expression and growth inhibition by IL-2, carcinoma cells were transduced with IL-2R alpha and IL-2R gamma cDNAs or IL-2R beta antisense cDNA. Transfectants with the IL-2R alpha gene expressed high levels of the alpha- and beta-receptor chains and showed increased binding of [125I]IL-2. Exogenous IL-2 at the picometer concentrations inhibited their growth, and Abs to IL-2R alpha- or IL-2R beta-chains reversed the inhibition. After transduction of IL-2R beta antisense cDNA, gastric carcinoma (HR) cells no longer expressed IL-2R beta-chain, and their proliferation was depressed in the absence of exogenous IL-2. Transduction of IL-2R gamma-chain cDNA into tumor cells increased sensitivity to growth inhibition by exogenous IL-2 of a squamous cell carcinoma line, but not of HR or renal cell carcinoma lines. All of the parental and transduced tumor cell lines were found to constitutively express intracellular IL-2, detectable by immunostaining or flow cytometry of permeabilized cells. IL-2 was present on the surface of some tumor cells. Intracellular IL-2R beta and IL-2R gamma proteins were also detectable in tumor cells. Using reverse-transcription PCR combined with Southern blots or in situ hybridization, mRNA for IL-2 was found to be present in parental and transduced tumor cells. Expression on human carcinomas of IL-2R beta, inhibition of their growth by IL-2R beta antisense cDNA, and their ability to constitutively produce IL-2 and its presence on the cell surface, all suggest that endogenous IL-2 may play a role in tumor cell growth.
bcl-2 transgenic Lpr mice show profound enhancement of lymphadenopathy.
Authors: Reap E A , Felix N J , Wolthusen P A , Kotzin B L , Cohen P L , Eisenberg R A
Published: December 2022

The lpr gene encodes a defective form of the fas gene that mediates apoptosis, and its expression results in autoantibodies and massive lymphadenopathy. bcl-2, another gene locus that affects programmed cell death, acts to inhibit apoptosis. Since multiple mechanisms controlling programmed cell death may contribute to systemic autoimmunity, the effect of the bcl-2 transgene on the lpr model was examined by crossing bcl-2 transgenic and C57BL/6-lpr mice. Compared with bcl-2-/lpr mice, bcl-2+/lpr showed dramatic increases in lymphadenopathy and T cell accumulation, but not in autoantibodies or B cell numbers. Short term transfer studies demonstrated that double negative T cells normally have a limited lifespan, and their survival is enhanced by the bcl-2 transgene. Thus, defects in separate apoptosis mechanisms may combine to produce enhanced pathologic effects.
Treatment with okadaic acid reveals strong threonine phosphorylation of CD18 after activation of CD11/CD18 leukocyte integrins with phorbol esters or CD3 antibodies.
Authors: Valmu L , Gahmberg C G
Published: December 2022

The CD11/CD18 leukocyte integrins comprise three heterodimers involved in leukocyte adhesion. CD11/CD18 avidity may be regulated intracellularly, and the CD18 polypeptide has previously been shown to become phosphorylated in leukocytes after phorbol ester stimulation. The importance of phosphorylation in the regulation of CD11/CD18 avidity has, however, remained unclear. We have now activated T cells using phorbol esters, CD3, and CD44 Abs. Both phorbol ester and CD3 treatment activated protein kinase C. CD18 was shown to become more stably phosphorylated after phorbol ester treatment and more transiently so after CD3 stimulation. The phosphorylation was strongly augmented by okadaic acid, a serine/threonine phosphatase inhibitor. While phorbol ester treatment caused phosphorylation mainly on serine, in okadaic acid-pretreated cells, both phorbol ester treatment as well as CD3 stimulation revealed strong threonine phosphorylation. Since earlier mutational studies have demonstrated the functional importance of cytoplasmic threonine residues in CD18, the threonine phosphorylation reported here indicates the role of threonine phosphorylation in the regulation of CD11/CD18 avidity.
Activation of src-related tyrosine kinases by IL-3.
Authors: Anderson S M , Jorgensen B
Published: December 2022

The activation of src-related tyrosine kinases following IL-3 stimulation was examined in 32Dcl3 cells. Three src-related tyrosine kinases were activated following IL-3 stimulation: fyn, hck, and lyn. 32Dcl3 cells were transfected with retroviral vectors expressing each of these kinases and independent clones overexpressing each kinase were isolated. In cells overexpressing either fyn or hck, IL-3 stimulated a rapid increase in catalytic activity, which remained elevated longer compared with the kinetics observed in parental 32Dcl3 cells. An increase in the number of tyrosine-phosphorylated proteins in the presence and absence of IL-3 stimulation was observed in cells overexpressing fyn or hck. Transfection of 32Dcl3 cells with a retroviral vector encoding lyn also resulted in an elevated level of kinase activity, although the increase was not as dramatic as that observed with fyn or hck. Consistent with observations in parental 32Dcl3 cells, a high basal level of lyn kinase activity was observed in unstimulated lyn-transfected cells and IL-3 stimulation resulted in an approximate threefold increase in kinase activity. Overexpression of c-src in 32Dcl3 did not result in IL-3-stimulated activation of c-src, indicating specificity for fyn, hck, and lyn. While the overexpression of fyn, hck, or lyn in 32Dcl3 cells resulted in increased kinase activity and IL-3 stimulated tyrosine phosphorylation, it did not render the cells more sensitive to IL-3. These results suggests that in addition to the JAK2 tyrosine kinase, src-related kinases may play a significant role in signal transduction by cytokine receptors.
TABS, a T cell activation antigen that induces LFA-1-dependent aggregation.
Authors: Andrew D P , Yoshino T , Guh L , Martin-Simonet M T , Butcher E C
Published: December 2022

We describe here a mAb, DATK44, which induces homotypic aggregation of TK1 cells (a CD8 lymphoma). The glycoprotein recognized by DATK44 is of approximate m.w. 50 kDa and is expressed by monocytes, neutrophils, and subsets of lymphocytes, as well as on the high endothelial venule in peripheral and mesenteric lymph nodes. We named this Ag TABS (T cell activation B cell subset Ag), as TABS appears on T lymphocyte activation and is expressed at low and high levels by B cells. TABS is differentially regulated during T lymphocyte development, CD4+veCD8+ve thymocytes being TABShigh, while single positive CD4+ve and CD8+ve thymocytes are TABSdull CD4-veCD8-ve thymocytes are clearly split into dull and bright populations by the mAb. On exit from the thymus, T lymphocytes cease to express TABS, but T lymphocyte activation results in re-expression of TABS. TABS also shows tight coregulation with heat stable Ag on resting lymphocytes, but coexpression of these two molecules is lost upon lymphocyte activation. DATK44-induced aggregation of TK1 cells is temperature sensitive and blocked by pretreatment of the cells with metabolic inhibitors, genestein, dibutyl cAMP or cytochalasin B, while colchicine, staurosporin, sphingosine, okadaic acid, and W7 are without effect. DATK44-induced TK1 cell aggregation appears to be mediated by the LFA-1 pathway, as aggregation is blocked by anti-LFA-1 and anti-ICAM-1 mAbs but not by Abs capable of blocking CD44 and alpha 4 beta 7-mediated adhesion. Thus, TABS appears to be an adhesion inducer that selectively activates LFA-1-mediated lymphocyte aggregation.
Chemokine binding and activities mediated by the mouse IL-8 receptor.
Authors: Lee J , Cacalano G , Camerato T , Toy K , Moore M W , Wood W I
Published: December 2022

In humans and rabbits two similar IL-8R mediate the chemotaxis and activation of neutrophils induced by alpha chemokines. We present data to suggest that there is only one such IL-8R gene in mice. We then use mice with a targeted deletion of this gene to characterize alpha chemokine ligands that signal via the mouse IL-8R. These experiments show that mouse macrophage inflammatory protein 2 binds the receptor with high affinity (Kd = approximately 1.5 nM) and potently activates both an intracellular Ca2+ flux and a chemotactic response, events absent in neutrophils from receptor-deleted mice. Mouse KC is approximately 10-fold less potent. These results show that macrophage inflammatory protein 2 and KC potently activate mouse neutrophils via a unique IL-8R, and these proteins may function as the major proinflammatory alpha chemokines in mice.
Complement membrane attack complex, perforin, and bacterial exotoxins induce in K562 cells calcium-dependent cross-protection from lysis.
Authors: Reiter Y , Ciobotariu A , Jones J , Morgan B P , Fishelson Z
Published: December 2022

The complement membrane attack complex (MAC), the cytolytic granule protein of cytotoxic lymphocytes perforin, the streptococcal exotoxin streptolysin O (SLO), and the bee venom polypeptide melittin utilize a similar mechanism to incorporate into cell membranes, induce a Ca2+ influx and a rise in intracellular Ca2+ concentration, and produce cell lysis. At sublytic concentrations, these proteins trigger several cellular activities, including protein phosphorylation and synthesis. We have recently demonstrated that human leukemic cells treated with sublytic doses of human complement become more resistant to lytic complement doses. The study has now been extended to include three other pore-formers: murine perforin, SLO and melittin. As shown here, sublytic MAC induces in the K562 human erythroleukemic cells protection from lytic perforin, and vice versa, sublytic perforin induces protection from complement. Also, sublytic SLO and melittin increase resistance of K562 cells to lytic complement and perforin doses. The capacity of Ca2+ ionophores to induce resistance to the lytic proteins has been examined. Exposure of K562 cells to sublytic concentrations of ionomycin or A23187 for 1 h at 37 degrees C confers on them resistance to complement- and perforin-mediated lysis. The protective effects of the ionophores can be abrogated by chelation of extracellular Ca2+ and by inhibition of RNA or protein synthesis in the cells. These results indicate the following: 1) nucleated cells exposed to sublytic complement MAC, perforin, SLO, or melittin may become resistant to the four pore-formers. Physiologically, this may be regarded as an immunologic tachyphylaxis. 2) Ca2+ influx induced by these pore-formers is an essential and sufficient factor to produce this tachyphylaxis.
Role of the hypothalamus-pituitary-adrenal axis in the regulation of TNF production in mice. Effect of stress and inhibition of endogenous glucocorticoids.
Authors: Fantuzzi G , Di Santo E , Sacco S , Benigni F , Ghezzi P
Published: December 2022

Glucocorticoids (GC) are known inhibitors of TNF production and are increased by endotoxin (LPS) through a stimulation of the hypothalamus-pituitary-adrenal axis (HPAA), suggesting a feedback mechanism. We tried different approaches to study the role of the HPAA and endogenous GC in the regulation of TNF production. Cyanoketone, a GC synthesis inhibitor, inhibited corticosterone (CS) induction by LPS and increased LPS-induced serum TNF levels. Similar results were obtained by pretreating mice with anticorticotropin-releasing hormone Abs. Administration of adrenocorticotropic hormone increased blood CS and inhibited LPS-induced serum TNF. TNF production by mouse blood stimulated in vitro with LPS was inhibited by addition of CS. Blood from stressed or adrenocorticotropic-releasing hormone-treated mice (in which CS levels are elevated) stimulated ex vivo with LPS produced significantly less TNF than blood from control mice. Normal TNF production was restored by the addition of the GC receptor antagonist RU 38486, indicating a role for the elevated endogenous CS levels in the inhibition of TNF production. These data indicate that the HPAA is a major regulator of TNF production.
Vaccination with a recombinant V alpha domain of a TCR prevents the development of collagen-induced arthritis.
Authors: Rosloniec E F , Brand D D , Whittington K B , Stuart J M , Ciubotaru M , Ward E S
Published: December 2022

A recombinant TCR domain, derived from a T cell hybridoma that recognizes an immunodominant type II collagen epitope, was used to vaccinate against collagen-induced arthritis in DBA/1 (H-2q) mice. The recombinant TCR domain comprises VA11.1-JA17 gene segments and is representative of the V alpha domains expressed by oligoclonal T cells in this disease model. Vaccination of mice 28 days before type II collagen (CII) immunization with this V alpha 11.1 domain resulted in a significantly decreased incidence of arthritis in DBA/1 mice, in contrast to vaccination with a V alpha 4-J alpha 40 domain derived from an encephalitogenic T cell hybridoma specific for MBP. Disease blockade is accompanied by a reduction in T and B cell responses to both the immunogen bovine CII and the autoantigen murine CII. V alpha 4 and V alpha 11.1 domains were found to be highly immunogenic in DBA/1 mice, inducing both T cell proliferation and the production of V alpha specific Abs, indicating that the vaccination effect of V alpha 11.1 is specific. This is the first report of V alpha-directed immunotherapy in an autoimmune disease model and demonstrates the potential use of recombinant TCR vaccines in the treatment of autoimmune diseases that involve oligoclonal autoreactive T cells.
Novel vaccine approaches.
Authors: Ertl H C , Xiang Z
Published: December 2022

Recent advances in immunology, molecular biology, and peptide biochemistry have allowed the construction of subunit vaccines based on viral or bacterial recombinants, peptides or plasmid vectors. Although none of these approaches is currently being used for mass vaccination (with the exception or vaccinia-rabies G protein recombinant virus for wildlife immunization); several of them are undergoing clinical trials. None of these different vaccine constructs is likely to be totally effective in either the prevention of infectious diseases or immunotherapy of cancer. Recombinant viral vaccines such as those based on vaccinia or adenovirus as a rule induce potent immune responses. Vaccinia viruses have the added advantage of being heat stable and immunogenic after oral application, making them good candidates for wildlife immunization. Recombinants based on replication-defective adenoviruses are safer compared with vaccinia virus recombinants and, as far as our data indicate, have superior efficacy. In addition, they induce excellent immunity upon application to mucosal membranes, suggesting their usefulness as vaccines for infectious agents that enter through the airways or the genital tract. Peptides are of limited benefit in infectious disease prevention but might provide custom-made vaccines for cancer therapy. Genetic vaccines that were first described less than 5 years ago have already progressed to phase I clinical trials in healthy human adults. Provided that their safety can be confirmed, they might be suited to induce immunity to numerous agents.
CD59 and CD48 expressed by rat retinal pigment epithelial cells are major ligands for the CD2-mediated alternative pathway of T cell activation.
Authors: Liversidge J , Dawson R , Hoey S , McKay D , Grabowski P , Forrester J V
Published: December 2022

The alternative CD2-mediated pathway of T cell activation, which is independent of MHC/peptide recognition by the TCR/CD3 complex, is dependent upon two signals being received by the CD2 molecule. The natural ligand for CD2 is CD58, but controversy exists over alternative or additional ligands that could deliver the second signal in vivo. We have used rat retinal pigment epithelial cells (RPE), which lack temperature-insensitive ligands for CD2 adhesion, to study Ag-independent T cell activation. Rat RPE cells expressed high levels of CD59 and low levels of another potential CD2 ligand, CD48, both in vitro and in the in vivo model of experimental autoimmune uveoretinitis. When increasing numbers of syngeneic T cells were added to microwell cultures of rat RPE cells, the T cells, even in the absence of any exogenous stimulant in the cultures, underwent spontaneous proliferation. This effect required metabolically active RPE cells, and was IL-2 driven and enhanced in the presence of indomethacin. Proliferation was modulated by phosphatidylinositol-phospholipase C treatment of the RPE, and blocked by mAbs to CD59. Ab cross-linking of CD48 but not CD59 on the RPE was found to induce messenger RNA expression for IL-1 beta, which together with constitutively expressed IL-6 are required costimulatory factors for T cell activation through CD2. This is the first demonstration in a fully syngeneic system that bi-directional signaling involving CD59 and CD48 molecules expressed by physiologically normal, nonhematopoietic, cells can trigger T lymphocyte activation and proliferation through autocrine IL-2 production in the absence of Ag.
Neutrophils undergo apoptosis following ingestion of Escherichia coli.
Authors: Watson R W , Redmond H P , Wang J H , Condron C , Bouchier-Hayes D
Published: December 2022

Apoptosis is a distinct mechanism by which eukaryotic cells die. Neutrophils (PMN) play a fundamental role in the systemic inflammatory response syndrome. Clearance of PMN during resolution of the acute inflammatory process occurs by apoptosis, but factors inducing this process are unknown. The aims of this study were to determine whether PMN ingestion of Escherichia coli would result in PMN apoptosis and whether the mechanism was related to the respiratory burst. PMN from 10 healthy volunteers were cultured with different ratios of PMN:E. coli (1:0 to 1:25) for 12 h. Apoptosis was then assessed by propidium iodide DNA staining, morphology, gel electrophoresis, and Fc gamma RIII expression. There was a significant induction of PMN apoptosis on incubation with E. coli at a ratio of 1:10 and 1:25 PMN:E. coli as well as decreases in Fc gamma RIII. This correlated with increased ingestion of FITC-labeled E. coli and intracellular reactive oxygen intermediates after a 2-h coculture. To clarify the role of reactive oxygen intermediates in E. coli-induced PMN apoptosis, we assessed the effects of the antioxidants catalase, DMSO, glutathione, and N-acetylcysteine. There was a significant decrease in E. coli-induced PMN apoptosis on incubation with DMSO (1.0%), glutathione (25 mM), and N-acetylcysteine (25 mM) compared with control PMN:E. coli. This study demonstrates for the first time that E. coli induces PMN apoptosis through an oxygen-dependent mechanism. The removal of effete PMN by the process of apoptosis rather than necrosis may be teleologically beneficial during Gram-negative septicemia.
Phage display cloning and characterization of an immunogenetic marker (perinuclear anti-neutrophil cytoplasmic antibody) in ulcerative colitis.
Authors: Eggena M , Targan S R , Iwanczyk L , Vidrich A , Gordon L K , Braun J
Published: December 2022

Ulcerative colitis (UC) is genetically associated with a marker serum Ab (pANCA), identified by its reactivity with a neutrophil Ag. This study utilized phage display technology to clone and characterize pANCA, which has resisted conventional isolation strategies. Since spontaneous pANCA-secreting B cells are detectable in UC lamina propria lymphocytes, this cell source was used to construct a complete IgG1-kappa Ig library. Selection of phage by panning with fixed neutrophils yielded a 195-fold enrichment after five cycles of panning. BstN1 fingerprinting of the enriched library revealed two predominant clones, and DNA sequencing demonstrated highly homologous heavy and light chain variable region segments. Clones were reengineered to express soluble Fab, and neutrophil binding was verified by ELISA. Detailed studies with the two recombinant Fabs, NANUC-1 and -2, validated their identity with serum pANCAs by the criteria of immunofluorescence, confocal microscopy, and DNase I sensitivity. NANUC-1 and -2, like serum UC-pANCA, lack reactivity with previously characterized ANCA-reactive neutrophil proteins and thus detect a novel Ag(s). This study demonstrates the feasibility of selecting phage display Ab libraries on uncharacterized biologic substrates to isolate marker Abs of pathogenic importance.
Adenosine enhances IL-10 secretion by human monocytes.
Authors: Le Moine O , Stordeur P , Schandené L , Marchant A , de Groote D , Goldman M , Devière J
Published: December 2022

Adenosine is a potent endogenous antiinflammatory agent released by cells under metabolically unfavorable conditions. Its effects on the production of IL-10 by human monocytes were presently investigated. Pre-incubation with adenosine dose-dependently enhanced IL-10 release by TNF stimulated human monocytes (+29, +58, and +116% at 1, 10, and 100 muM, respectively.) Adenosine also significantly enhanced IL-10 production after hydrogen peroxide and LPS stimulation and dose-dependently inhibited TNF secretion. Pre-incubation was not mandatory to achieve these effects, since addition of adenosine at the time of or 30 min after the stimulus led to the same results. Blocking IL-10 with anti-IL-10 mAbs partially restored adenosine-induced TNF inhibition. The enhanced IL-10 production was not observed when cells were preincubated with adenosine A1 or A2 receptor agonists (R-phenylisopropyladenosine, 5'-N-ethylcarboxamido-adenosine, and 2-chloroadenosine) and was not affected by pretreatment with theophyllin, an antagonist of both A1 and A2 receptors, or with dipyridamole, an inhibitor of adenosine cellular uptake. In conclusion, adenosine, in the submillimolar concentration range, increases IL-10 secretion by stimulated monocytes. This phenomenon participates in TNF inhibition, a known property of adenosine, but is not mediated through the occupancy of A1 or A2 receptors. This may represent a novel antiinflammatory property of adenosine by which it could modulate inflammation and limit ischemia-reperfusion injury.
Toxoplasma gondii infection induces specific nonresponsiveness in lymphocytes bearing the V beta 5 chain of the mouse T cell receptor.
Authors: Denkers E Y , Caspar P , Hieny S , Sher A
Published: December 2022

We recently reported a superantigen activity associated with Toxoplasma gondii tachyzoites that in vitro induces preferential expansion of V beta 5+ T lymphocytes following parasite stimulation of nonimmune cells. In the experiments presented in this work, V beta 5+ lymphocyte function was examined ex vivo using mice undergoing chronic and acute infection with the avirulent parasite strain ME49 or acutely infected with the attenuated mutant ts-4. Cells bearing the TCR V beta 5 chain were found to be increased by 1.5- to twofold during acute infection, whereas during the chronic phase, modest decreases (approximately 20%) in cells of the latter subset were observed. When splenocytes from chronically infected animals were stimulated in vitro with tachyzoites, the preferential expansion of V beta 5+ lymphocytes seen using cells from normal mice was not observed. Furthermore, when purified T lymphocytes were cultured with plate-bound V beta 5-specific mAb, we found that in contrast to normal and acutely infected animals, cells from chronically infected and ts-4-vaccinated mice were nonresponsive to TCR-induced stimulation (70 to 90% reduction relative to normal cells). In control experiments, mAb to CD3 and V beta 8 elicited normal responses in the same animals. Similarly, in contrast to normal splenocytes, cells from chronically infected mice failed to produce IFN-gamma in response to anti-V beta 5 mAb. These data indicate that V beta 5+ cells are rendered nonresponsive as a result of in vivo encounter with T. gondii, and as such they provide the first demonstration of V beta-specific anergy induced by a protozoan parasite.