bluuebunny/crossref_metadata_2025_split huggingface dataset:
Two proteolytic pathways for down-regulation of the barrier molecule CD43 of human neutrophils.
Authors: Remold-O'Donnell E , Parent D 
Published: December 2022

Abstract
CD43, an anionic rod-like mucin molecule on white blood cells, is thought to provide a barrier that prevents interactions of other surface molecules and acts as negative regulator of cell function. As a correlate, CD43 is expected to be altered or down-regulated when blood cells are functionally activated. This study examines CD43 of blood neutrophils before and after treatment with known activating agents. Flow cytometry indicated that PMA and A23187, and to a much lesser extent, FMLP and IL-8, decrease neutrophil expression of CD43. Two separate mechanisms were identified for CD43 down-regulation. Both are proteolytic processes. PMA-induced down-regulation is a rapid process involving proteolysis at a minimum of two sites, one within the N-terminal distal region recognized by mAbs and the other at a membrane-proximal site. The PMA-induced protease, cd43' ase, is characterized by insensitivity to DFP, TLCK, leupeptin, pepstatin, and 1,10 phenanthroline (&lt; 5 mM). PMA-induced CD43 down-regulation is extensive but never complete, terminating at approximately 10 min after down-regulating 65 to 85% of molecules, and thereby converting neutrophils from dense to sparse CD43 expression. The second CD43 down-regulation mechanism, although likely a regulated event in vivo, occurred slowly in this study in neutrophils incubated without additives; the process is not affected by PMA, involves the action of a DFP-sensitive protease, releases N-terminal mAb-reactive fragments of 52 kDa or 40 kDa and can be mimicked by exogenous neutrophil elastase. The complexity and apparent tight regulation described here for the two down-regulatory mechanisms are consistent with an important role for CD43 in preventing or dampening cell surface interactions of blood neutrophils.
Autoantibody responses to the "native" 52-kDa SS-A/Ro protein in neonatal lupus syndromes, systemic lupus erythematosus, and Sjogren's syndrome.
Authors: Buyon J P , Slade S G , Reveille J D , Hamel J C , Chan E K 
Published: December 2022

Abstract
Abs to the 52-kDa SS-A/Ro protein are found in high prevalence in patients with Sjogren's syndrome (SS) and mothers whose children have the neonatal lupus syndrome (NLS). This study further defines the specificity of this response. By ELISA, 97% of 59 mothers of offspring with NLS had Abs to the 52-kDa recombinant protein compared with 80% in 132 non-NLS sera with anti-SS-A/Ro Abs (p &lt; 0.004). Antigenic regions on the 52-kDa protein were evaluated by immunoprecipitation of [35S]-radiolabeled in vitro translation products. Ninety-five percent of 99 sera that contained anti-52-kDa Abs by ELISA reacted with a large fragment spanning amino acids (aa) 1-291. Two antigenic regions were identified, aa169-291 containing the leucine zipper that was recognized by 83% of the anti-52-kDa sera tested and aa1-78 containing the zinc finger domains that was recognized by only half the sera. No sera immunoprecipitated this N-terminal fragment exclusively. Recognition of one or both regions was not unique to any clinical subset of patients; however, a greater number of sera from patients with SS contained both specificities, whereas asymptomatic mothers whose children had NLS comprised the only clinical group in which the majority recognized the central region of the molecule. Reactivity with both epitopes was demonstrated significantly more often in sera with high titers of Abs to the 60-kDa rSS-A/Ro protein by ELISA in association with the anti-52-kDa response compared with anti-52-kDa responses associated with low titers of anti-60-kDa Abs (p &lt; 0.04). Eighty-one percent of 16 sera that recognized the N-terminal epitope were from patients with the combination of HLA-DRB1*0301, DQA1*0501, and DQB1*0201 alleles, compared with 30% of 10 that recognized only the central epitope (p &lt; 0.02). In summary, this study demonstrates that there are at least two antigenic determinants on the 52-kDa SS-A/Ro protein, one "immunodominant" and the other recognized by a more "restricted" subset of anti-52-kDa SS-A/Ro Abs.
Adhesion through the LFA-1 (CD11a/CD18)-ICAM-1 (CD54) and the VLA-4 (CD49d)-VCAM-1 (CD106) pathways prevents apoptosis of germinal center B cells.
Authors: Koopman G , Keehnen R M , Lindhout E , Newman W , Shimizu Y , van Seventer G A , de Groot C , Pals S T 
Published: December 2022

Abstract
In the germinal center (GC), B cells are either selected to become memory cells or are eliminated through the process of programmed cell death. FDC which are intimately associated with the GC B cells are thought to be important in this selection process. Previously, we have shown that the LFA-1 (CD11a/CD18)-ICAM-1 (CD54) and VLA-4 (CD49d)-VCAM-1 (CD106) adhesion pathways are involved in FDC-B cell interaction. In the present study, we have explored whether these adhesive interactions contribute to the process of B cell selection by studying the effects on apoptosis of GC B cells. Using FDC and B cells derived from human tonsils, we found that only B cells adherent to FDC remain viable: disruption of FDC-B-cell clusters with mAb against LFA-1 alpha (CD11a), VLA-4 (CD49d), ICAM-1 (CD54), or VCAM-1 (CD106) results in apoptosis of the B cells. Furthermore, we found that GC B cells, upon adhesion to plastic-coated purified ICAM-1 (CD54) or VCAM-1 (CD106), show diminished apoptosis. Importantly, we observed that, at low concentration, ICAM-1 (CD54) and VCAM-1 (CD106) act synergistically with anti-IgM, in inhibiting apoptosis. Together, our data strongly suggest that adhesion of B cells via the LFA-1 (CD11a/CD18)-ICAM-1 (CD54) pathway and VLA-4 (CD49d)-VCAM-1 (CD106) pathway contributes to B cell selection.
Thymic CD45 tyrosine phosphatase regulates apoptosis and MHC-restricted negative selection.
Authors: Ong C J , Chui D , Teh H S , Marth J D 
Published: December 2022

Abstract
The acquisition of immunologic self-tolerance is governed, in part, by selection mechanisms that occur during intrathymic T cell ontogeny. Although considerable data exist for the molecular basis of mature T cell signal transduction, the enzymes that participate in thymic TCR selection processes have remained unidentified. We report that augmented thymic expression of the CD45R0 protein tyrosine phosphatase increased the efficacy of TCR-mediated apoptosis and MHC-restricted negative selection of HY TCRs in vivo. Additionally, augmented CD45R0 expression resulted in the activation of endogenous p56lck tyrosine kinase in CD4+CD8+ thymocytes. These results identify a cellular enzyme, the CD45R0 protein tyrosine phosphatase, involved in the regulation of apoptosis and TCR selection mechanisms during CD4+CD8+ thymocyte differentiation.
Ig heavy chain extracellular spacer confers unique glycosylation of the Mb-1 component of the B cell antigen receptor complex.
Authors: Pogue S L , Goodnow C C 
Published: December 2022

Abstract
A unique functional role for the B cell Ag receptor, IgD, has not yet been identified. A number of properties of IgD, such as distinct intron-exon organization and a conserved pattern of developmental expression, suggest a selective evolutionary advantage for this receptor isotype. To explore structural features of IgD that may confer unique functions, chimeric Ag receptors were generated in which small segments of the IgD heavy chain membrane proximal regions were substituted for corresponding segments of the IgM heavy chain. Polypeptides that associate with the Ig receptors were analyzed. Mb-1/Ig-alpha, a signal transduction molecule, is known to be glycosylated in a distinct manner when associated with IgD compared to when associated with other isotypes. We report that this differential glycosylation results because one N-linked carbohydrate on Mb-1 fails to be processed into an Endo-H-resistant form when associated with IgM or IgG, whereas both N-linked carbohydrates are processed on Mb-1 associated with IgD. By preparing chimeric IgM-IgD heavy chains, substitution of the IgD extracellular spacer segment alone was found to be necessary and sufficient to confer an IgD-type glycosylation pattern on the Mb-1 molecule. This altered glycosylation pattern, however, did not confer a detectable difference in calcium mobilization or in protein tyrosine phosphorylation upon receptor stimulation. Interestingly, a similar altered glycosylation pattern has been reported for the T cell Ag receptor complex in which carbohydrates on the CD3 delta-chain are fully processed in gamma delta-T cell receptors but only partially processed in alpha beta-T cell receptors.
Interaction of Staphylococcus aureus with human neutrophils and the down-regulation of TNF receptors.
Authors: Ferrante A , Martin A J , Bates E J , Kowanko I C , Harvey D P , Parsons D , Rathjen D A , Russ G , Dayer J M 
Published: December 2022

Abstract
We have shown previously that pre-exposure of neutrophils to TNF significantly enhanced their killing of opsonized Staphylococcus aureus. We now demonstrate that the ability of TNF to enhance the bactericidal activity is dependent on preincubation time; enhancement was still evident when TNF and bacteria were added simultaneously to neutrophils but if TNF addition was delayed by 5 min, no enhancement was seen. Evidence is presented that suggests that this could be related to a down-regulation of TNF receptors by the bacteria, but in addition, the release of TNF receptor fragments may contribute to the inhibition observed. Scatchard analyses demonstrated a decrease from approximately 3000 TNF receptor (receptor binding) sites per cell to 450 following treatment with S. aureus, but essentially no change in receptor affinity. Using mAb directed against the type A (75 kDa) receptor (utr-1) and the type B (55 kDa) receptor (htr-9), it was found that the expression of both receptors was decreased following treatment with the bacteria. The time course of loss of these receptors showed that the surface expression of both molecules was markedly decreased by 5 min which correlated with the loss in ability of TNF to enhance the bactericidal activity. In contrast to changes seen in the binding of TNF, similarly treated neutrophils showed essentially no change in the binding of radiolabeled tripeptide FMLP and, if anything, an increase in the expression of the CD11b Ag (CR3 receptor). When another phagocytic stimulus was used, opsonized fungi (Torulopsis glabrata), a similar depression of TNF binding was also found, but opsonized sheep erythrocytes had no effect on the TNF binding, suggesting that the effects on the TNF receptor cannot be explained simply on the basis of particle phagocytosis.
Cell-surface protein identified on phagocytic cells modulates the C1q-mediated enhancement of phagocytosis.
Authors: Guan E , Robinson S L , Goodman E B , Tenner A J 
Published: December 2022

Abstract
C1q, a subunit of the first component of the classical C pathway, binds to specific cells of the immune system, triggering a variety of cellular responses. To identify the functional C1qR on phagocytic cells, mAbs were generated by immunization with either C1q-binding proteins isolated from U937 cells or intact U937 cells. Immunoprecipitation followed by Western blot analysis demonstrated that three mAbs, designated R139 (IgG2b), R3 (IgM), and U40.3 (IgG1), recognize the same 100,000 M(r) protein (126,000 M(r) under reducing conditions). These mAbs also co-immunoprecipitate CD43 from detergent extracts of U937, consistent with the possibility that this C1qR is a multi-subunit structure. Two Abs, R3 and R139, but not U40.3, consistently inhibited the enhancement of phagocytosis by monocytes adhered to either C1q or the collagen-like fragment of C1q (C1q-CLF). Interestingly, binding inhibition studies demonstrated that neither R139 nor U40.3 blocked the binding of [125I]C1q-CLF to U937 cells, whereas R3 did inhibit 35 to 45% of the binding of [125I]C1q-CLF to these cells. Thus, the three mAbs recognize distinct epitopes of a 100,000 M(r) polypeptide that is a component of the monocyte C1qR that modulates phagocytosis. All three mAbs recognize the extracellular domain of the molecule on neutrophils, monocytes, and U937 cells, but were not reactive with CEM or RAJI cells, T and B lymphoblastoid cell lines, respectively. Furthermore, none of these three mAbs inhibited or mimicked the C1q-mediated stimulation of superoxide production by neutrophils, suggesting that the C1qR that mediates the enhancement of phagocytosis differs in at least some critical parameter from the C1qR that mediates superoxide generation by the neutrophil.
Differential roles of two types of the TNF receptor in TNF-induced cytotoxicity, DNA fragmentation, and differentiation.
Authors: Higuchi M , Aggarwal B B 
Published: December 2022

Abstract
Two different types of TNF receptors, the p60 receptor with a molecular mass of 60 kDa and the p80 receptor with a mass of 80 kDa, have been identified. TNF exhibits a wide variety of biologic actions, but which receptor is responsible for these biologic actions is not well characterized. In the present study, we examined the roles of the p60 and p80 receptors in three different TNF-induced biologic actions: 1) cytotoxicity; 2) DNA fragmentation; and 3) differentiation to macrophages. Analysis of TNF actions on various tumor cell lines revealed that TNF-induced cytotoxicity occurred in cells that expressed the p60 receptor, irrespective of expression of the p80 receptor. In contrast, DNA fragmentation and differentiation were observed only in cells that expressed both receptor types. Additionally, the specific Ab to each receptor were used to examine the roles of both receptors in the myelogenous leukemia cell line, ML-1a. Anti-p60 Ab alone showed cytotoxicity but little DNA fragmentation and differentiation, and anti-p80 Ab alone showed no effects. When these Abs were added in the presence of TNF, each independently, and almost completely, inhibited TNF-induced DNA fragmentation and differentiation. We also found that both Abs together synergistically induce differentiation and DNA fragmentation. These results indicate that signals through the p60 receptor are essential to induce cytotoxicity, but signals through both the p60 and p80 receptors are necessary, and act synergistically, for DNA fragmentation and differentiation.
Binding of the terminal mannosyl units of lipoarabinomannan from a virulent strain of Mycobacterium tuberculosis to human macrophages.
Authors: Schlesinger L S , Hull S R , Kaufman T M 
Published: December 2022

Abstract
Recent studies from this laboratory have demonstrated that macrophage phagocytosis of virulent strains (Erdman and H37Rv), but not the attenuated H37Ra strain of Mycobacterium tuberculosis, is mediated by phagocyte mannose receptors (MR) in addition to complement receptors (CR1 and the leukocyte integrins CR3 and CR4). Lipoarabinomannan (LAM) is a major surface lipoglycan of M. tuberculosis. LAM from the Erdman strain (Man-LAM) contains mannose oligosaccharides at the terminal portions of the molecule. This study investigated the ability of ManLAM to serve as a microbial ligand in adherence to human monocyte-derived macrophages (MDM). Polystyrene microspheres were coated with known amounts of purified ManLAM, LAM without the terminal mannosyl units from an avirulent mycobacterium (AraLAM), lipomannan (LM), or buffer and incubated with MDM monolayers in the absence of serum. The presence of LAM on microspheres was confirmed by indirect immunofluorescence studies. Microspheres coated with ManLAM demonstrated a more than threefold increase in adherence to MDM when compared with microspheres coated with AraLAM, LM, or buffer and the low levels of adherence of microspheres in the latter three groups were comparable. Compared with control monolayers, selective down-modulation of MDM MR on a mannan substrate abrogated the enhanced adherence of microspheres mediated by ManLAM. Adherence of microspheres coated with AraLAM, LM, or buffer was not influenced by MR modulation. To confirm the importance of the terminal mannosyl units of ManLAM in the enhanced adherence of ManLAM microspheres to MDM, these units were selectively removed by exomannosidase treatment. The structure of LAM products before and after enzyme treatment was confirmed by high performance anion exchange chromatography with pulsed amperometric detection. Removal of the terminal mannosyl units abolished the capacity of ManLAM to mediate enhanced adherence of microspheres to MDM. Finally, preincubation of Erdman M. tuberculosis with CS-40, a mAb directed against LAM, resulted in a consistent inhibition of adherence of the bacteria to MDM (up to 49% inhibition), confirming a role for ManLAM on intact bacteria in adherence to MDM. Thus, we provide evidence for a novel receptor-ligand pathway in phagocytosis of M. tuberculosis that consists of MR on macrophages and mannosyl units at the terminal end of ManLAM, a major microbial surface lipoglycan.
Inactivation of nitric oxide synthase after prolonged incubation of mouse macrophages with IFN-gamma and bacterial lipopolysaccharide.
Authors: Vodovotz Y , Kwon N S , Pospischil M , Manning J , Paik J , Nathan C 
Published: December 2022

Abstract
Large amounts of nitric oxide (NO) are produced by the inducible isoform of NO synthase (iNOS) in many cell types once the iNOS gene is transcriptionally activated. In primary mouse peritoneal macrophages elicited by thioglycolate broth, expression of iNOS follows treatment with IFN-gamma and is synergistically increased by the addition of bacterial LPS. Expression of iNOS is suppressible at transcriptional and translational levels by certain cytokines and microbial products. The present study describes a novel form of inactivation of iNOS that is post-translational and nondegradative. Mouse peritoneal macrophages cultured in the presence of IFN-gamma alone or IFN-gamma plus LPS rapidly depleted the medium of L-arginine, a substrate for iNOS, and stopped producing NO. Repletion of L-arginine permitted cells treated with IFN-gamma alone to resume NO production for at least 5 days, leading to the release of more NO than macrophages were previously believed capable of generating. L-Arginine repletion also boosted NO production by macrophages cultured for up to 2 to 3 days in the presence of IFN-gamma plus LPS, but thereafter, iNOS was inactive in these cells whether or not L-arginine was repleted. Activity of iNOS could be restored by adding both L-arginine and fresh IFN-gamma with or without LPS, likely reflecting the synthesis of new enzyme. However, the inactivation of iNOS seen late in culture with a single application of IFN-gamma plus LPS could be attributed neither to loss of iNOS protein nor to its autoinactivation by NO. Thus, LPS, a co-inducer of iNOS, causes macrophages to inactivate iNOS about 3 days after the onset of its induction. The mechanism, which remains to be identified, is novel for iNOS, in that it decreases neither its amount nor its apparent molecular mass.
Maturational changes in CD4+ cell subsets and lymphokine production in BXSB mice.
Authors: Chu E B , Ernst D N , Hobbs M V , Weigle W O 
Published: December 2022

Abstract
CD4+ cells are thought to play a significant role in the development of lupus-like disease in a variety of autoimmune disease-prone mouse strains. In one such strain, BXSB/MpJScR, male mice develop severe lupus-like symptoms early in life but females do not. In this study, splenic CD4+ cells from male and female BXSB mice were evaluated for age-related changes in: 1) membrane expression of CD4+ cell subset markers (1, 2, and 4 mo) and activation Ags (4 mo) and 2) the capacity to proliferate and produce cytokines (4 mo) in response to polyclonal stimuli. CD4+ cells from females of all age groups and from younger males were predominantly CD44lo, CD45RBhi, MEL-14hi, and 3G11hi (phenotypes associated with naive T cells). In contrast, 4-mo-old males were predominantly CD44hi, CD45RBlo, MEL-14lo, and 3G11lo (phenotypes associated with activated/memory T cells). Furthermore, an increased constitutive expression of the activation Ags RL388, IL-2R, and TfR was observed in CD4+ cells of 4-mo-old male BXSB mice in comparison with age-matched females. In 3-day cultures, purified CD4+ cells from 4-mo-old males proliferated significantly less than cells from age-matched females in response to plate-bound anti-CD3 epsilon (2C11i). The reduced proliferation was restored in large part by PMA and ionomycin. CD4+ cells from older males generally produced increased amounts of IFN-gamma and IL-4 and significantly less IL-2 than age-matched females in response to either stimulus (IL-2 mRNA was also decreased in response to 2C11i). Taken together, these studies suggest that profound phenotypic and functional changes occur with age in the CD4+ cells of male BXSB mice that are indicative of an activated state.
Characterization of cat dander-specific T lymphocytes from atopic patients.
Authors: van Neerven R J , van de Pol M M , van Milligen F J , Jansen H M , Aalberse R C , Kapsenberg M L 
Published: December 2022

Abstract
Fel d I, the major cat dander allergen, is recognized by serum IgE of more than 80% of all cat-allergic patients. Because IgE synthesis by B lymphocytes is under the control of T lymphocytes, we studied the specificity and lymphokine production profiles of cat dander-specific T lymphocytes. Polyclonal cat dander-specific T cell lines were found to react with purified Fel d I, but not with cat albumin, the only other characterized cat allergen. Similarly, within a panel of CD4+ T lymphocyte clones (TLC) that was generated from these cat dander-specific T cell lines, 5 of 16 TLC were found to react with Fel d I, and 0 of 16 with cat albumin. The remaining 11 TLC were shown to recognize at least two different proteins. In general, the TLC had a high IL-4/IFN-gamma production ratio, and could recognize the cat dander extract in an HLA-DR, HLA-DQ, or HLA-DP restricted manner. In addition, five distinct T cell epitopes of Fel d I were identified by using a panel of overlapping synthetic peptides of both chains of Fel d I. The data presented here indicate that, even though multiple proteins in cat dander extract are recognized by T lymphocytes of allergic patients, Fel d I, the major IgE binding allergen, is also important in T cell activation. The fact that the cat-specific TLC are Th2-like indicates that these cells may play an important role in the pathophysiology of allergic responses to cat allergens. However, the diversity of HLA-class II restriction of cat dander- and Fel d I-specific TLC and the presence of multiple T cell epitopes in the allergen may complicate future immunotherapies.