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Morphine modulation of plasmodial-antigens-induced colony-stimulating factors production by macrophages.

Morphine abuse is known to cause immunosuppression and enhanced host susceptibility to malaria. We studied the effect of morphine on the Plasmodium berghei total-parasite-antigens soluble in culture medium (P.b.SA)-induced production of colony-stimulating factors (CSFs) by mouse peritoneal macrophages, in vitro. Morphine exerted a concentration-dependent biphasic modulatory effect; at 1 x 10(-4)-1 x 10 x 10(-6) M it slightly inhibited, whereas at 1 X 10(-8)-1 x 10(-10) M it augmented the production of CSFs. However, at 1 x 10(-12) M concentration the augmenting effect of morphine was significantly (p<0.05) diminished. Selective agonists of delta- (DPDPE) and mu- (DAGO) opioid receptors also respectively, inhibited and augmented the production of CSFs. The CSFs appear to be synthesized de novo as cycloheximide (50.0 microg/ml) completely inhibited their production. Naloxone ( 1 x 10(-5) M) lacked any effect on the inhibitory effect of morphine; however, at 1 x 10(-3) M it exerted partial blocking effect. Conversely, at 1 x 10(-5) M naloxone significantly (p<0.05) blocked the augmenting effect of morphine. These results suggest that morphine via opioid receptors, in a concentration-dependent biphasic manner, modulated the P.b.SA-induced de novo production of CSFs by macrophages, in vitro.

Adjuvants, Immunologic↗

Induction of T-cell hyporesponsiveness by intrahepatic modulation of donor antigen-presenting cells.

In this study, we examined the ability of varying populations of donor cells from B6 mice to induce hyporesponsiveness in T lymphocytes from C3H mice in vitro and in vivo. Small, resting B lymphocytes were inefficient stimulators of T-lymphocyte proliferation compared to splenic mononuclear cells (SMNC) and lipopolysaccharide (LPS)-induced B-cell blasts in vitro (P < 0.05). Pretreatment of SMNC with anti-B7-1 or anti-intracellular adhesion molecule-1 (ICAM-1) monoclonal antibodies (mAb) similarly resulted in inefficient stimulation of T-cell proliferation in vitro (P < 0.05). However, in vivo, only intrahepatic, but not intravenous, injection of donor cells into C3H mice resulted in decreased T-lymphocyte proliferation in response to restimulation by alloantigen. This effect was most pronounced following intrahepatic injection of resting B lymphocytes or SMNC pretreated with anti-ICAM-1 mAb compared to uninjected or intravenously injected mice (P < 0.05). The hyporesponsiveness was associated with an increased production of interleukin-4 (IL-4) by the responder T lymphocytes and correlated with enhanced skin allograft survival. These data demonstrate that intrahepatic injection of donor-derived cells induces T-lymphocyte hyporesponsiveness. The mechanism appears to be modulated by an ICAM-1-mediated signal resulting in expansion of an IL-4-producing T-lymphocyte population.

Animals↗

Mitochondrial modulation of maternally transmitted antigen: analysis of cell hybrids.

Maternally transmitted antigen (Mta) is a murine cell surface class I-like antigen that is defined by specific cytotoxic lymphocyte reactivity. Mta is unique in that its expression requires cooperation between genetic elements both in the Qa/Tla region of chromosome 17 and in the cytoplasm. In view of the known cytoplasmic, and thus maternal, inheritance of mitochondria, we have directly assessed their potential involvement in Mta expression. The mitochondria-specific lethal dye rhodamine 6G (R6G) was used to control the input of mitochondria into cell hybrids. The parental lines, one of BALB/c and one of NZB origin, were known to differ in Mta and mtDNA phenotype. Our data show that most control BALB/c-NZB hybrids expressed the BALB/c Mta phenotype and likewise contained only BALB/c-type mtDNA. The NZB Mta phenotype was not coexpressed in the control hybrids. However, when the mitochondrial contribution from BALB/c was prevented by R6G treatment, the majority of the resultant hybrids expressed only the NZB Mta type and likewise contained only NZB mtDNA. The exceptional R6G-treated hybrids that continued to express the BALB/c Mta phenotype likewise contained only BALB/c mtDNA. Thus, in every case the mtDNA phenotype correlated with the Mta phenotype of the cells. Together, the data support the remarkable conclusion that mitochondria modulate the phenotypic expression of a cell surface molecule.

Animals↗

Occupancy of an adhesive glycoprotein receptor modulates expression of an antigenic site involved in cell adhesion.

Binding of ligands that contain Arg-Gly-Asp to adhesion receptors induces cell spreading and aggregation and alters gene expression, possibly due to conformational changes within occupied adhesion receptors. PMI-1 is a monoclonal antibody which reacts with the platelet fibrinogen receptor, glycoprotein IIb-IIIa, and reports such a conformational change. ADP stimulation of platelets results in a fibrinogen-dependent increase in binding of the PMI-1 antibody. Peptides containing Arg-Gly-Asp also reversibly increase the binding of this antibody to cells and to purified glycoprotein IIb-IIIa. The PMI-1 antibody inhibits platelet adhesion and spreading on certain substrata (Shadle, P. J., Ginsberg, M. H., Plow, E. F., and Barondes, S. H. (1984) J. Cell Biol. 99, 2056-2060); thus this occupancy-modulated site may participate in adhesive function.

Adenosine Diphosphate↗

Adult Schistosoma mansoni worms positively modulate soluble egg antigen-induced inflammatory hepatic granuloma formation in vivo. Stereological analysis and immunophenotyping of extracellular matrix proteins, adhesion molecules, and chemokines.

Synchronized liver granulomas were induced by injecting Sepharose beads to which SEA soluble egg antigen (SEA) or the concanavalin A binding fraction of SEA had been coupled into a mesenteric vein in naive, single-sex (35 days) and bisexually (28 days) Schistosoma mansoni-infected and Plasmodium berghei-immunized mice. Stereological analysis revealed that peak granuloma formation was already reached 8 days after injection in single-sex infected mice compared with 16 days in naive animals. No difference in granuloma formation between naive and P. berghei-immunized animals and between unisexually and bisexually S. mansoni-infected mice was observed. This suggests that the positive immunomodulatory effect on the granulomogenesis is worm specific and not likely to be due to arousal of the immune system by unrelated factors, nor is it influenced by the gender or degree of maturation of female worms. At all stages in time, the concanavalin A binding-fraction-induced granulomas reached only 65 to 70% of the volume of SEA-induced granulomas. Immunophenotyping of extracellular matrix proteins around deposited heads revealed that fibronectin was the dominant extracellular matrix protein and that also type I and IV collagen and laminin were deposited. Temporal analysis of the expression of the adhesion molecules ICAM-1, LFA-1, VLA-4, and VLA-6 was performed. Morphological evidence is presented for the role of adhesion molecules in the initiation and maintenance of hepatic granuloma formation. The chemokine monocyte chemoattractant protein-1 was expressed in the granuloma and in hepatic artery branches. From these data, it is concluded that adult S. mansoni worms positively modulate schistosomal hepatic granuloma formation in vivo. Adhesion molecules and chemokines play important roles in schistosomal granuloma formation.

Animals↗

The proteolytic environment involved in MHC class II-restricted antigen presentation can be modulated by the p41 form of invariant chain.

During biosynthesis, MHC class II associates with invariant chain which exists in two forms, p31 and p41. Both forms of invariant chain prevent peptide binding to class II, facilitate transport, and enhance class II localization to Ag-processing compartments. In spite of these shared functions, presentation of some Ags can be selectively enhanced by expression of p41. Here we show that p41 can function as a protease inhibitor: 1) the functional and biochemical consequences of p41 expression can be mimicked by inhibiting cysteine proteases in vivo; 2) the amount of intracellular active cysteine proteases is dramatically decreased in p41-positive cells; and 3) a polypeptide corresponding to the p41-unique region is a potent inhibitor of cathepsin L in vitro. These data suggest that p41 can enhance Ag presentation by reducing the proteolytic activity of the Ag-processing compartment, thus protecting a subset of antigenic epitopes from excessive degradation.

Animals↗

In vivo treatment with monoclonal anti-I-A antibodies: disappearance of splenic antigen-presenting cell function concomitant with modulation of splenic cell surface I-A and I-E antigens.

A single injection of anti-I-Ak antibody (AB) into H-2k mice resulted in abrogation of splenic antigen-presenting cell (APC) function for protein antigen-primed T cells or alloantigen-specific T cells. Spleen cells from anti-I-A-treated mice are not inhibitory in cell mixing experiments when using cloned antigen-specific T cells as indicator cells, thus excluding a role for suppressor cells in the observed defect. Also, nonspecific toxic effects and carry-over of blocking Ab were excluded as causes for the defect. Experiments with anti-I-Ak Ab in (H-2b X H-2k)F1 mice showed abrogation of APC function for T cells specific for both parental I-A haplotypes. In homozygous H-2k mice, anti-I-Ak treatment not only abrogated APC function for I-Ak-restricted cloned T cells but also for I-AekE alpha k-restricted cloned T cells. FACS analysis of spleen cells from anti-I-Ak-treated (H-2b X H-2k)F1 mice revealed the disappearance of all Ia antigens (both I-A and I-E determined), whereas the number of IgM-bearing cells was unaffected. The reappearance of APC function with time after injection was correlated with the reappearance of I-A and I-E antigen expression. In vitro incubation of spleen cells from anti-I-A-treated mice led to the reappearance of Ia antigen expression and APC function within 8 hr. Thus, it appears that B cells (as determined by FACS analysis) and APC (as determined by functional analysis) behave similarly in response to in vivo anti-I-A Ab treatment. We interpret these findings as suggesting that in vivo anti-I-A treatment temporarily reduces the expression of Ia molecules through co-modulation on all Ia-bearing spleen cells, thereby rendering them incompetent as APC. Such modulation of Ia molecules does not occur when spleen cells are incubated in vitro with anti-I-A antibodies. These results imply that a primary defect purely at the level of APC in anti-I-A-treated mice may be responsible for the observed T cell nonresponsiveness when such mice are subsequently primed with antigen.

Animals↗

Reversible phosphorylation at the C-terminal regulatory domain of p21(Waf1/Cip1) modulates proliferating cell nuclear antigen binding.

The p53-inducible gene product p21(WAF1/CIP1) plays a critical role in regulating the rate of tumor incidence, and identifying mechanisms of its post-translational regulation will define key pathways that link growth control to p21-dependent tumor suppression. A eukaryotic cell model system has been developed to determine whether protein kinase signaling pathways that phosphorylate human p21 exist in vivo and whether such pathways regulate the binding of p21 to one of its key target proteins, proliferating cell nuclear antigen (PCNA). Although human p21 expressed in Sf9 cells is able to form a complex with human PCNA, the inclusion of cell-permeable phosphatase inhibitors renders p21 protein inactive for PCNA binding. The treatment of this inactive isoform of p21 with alkaline phosphatase restores its binding to PCNA, suggesting that p21 expressed in Sf9 cells is subject to reversible phosphorylation at a key regulatory site(s). A biochemical approach was subsequently used to map the phosphorylation sites within p21, whose modification in vitro can inhibit p21-PCNA complex formation, to the C-terminal domain at residues Thr(145) or Ser(146). A phospho-specific antibody was developed that only bound to full-length p21 protein after phosphorylation in vitro at Ser(146), and this reagent was further used to demonstrate that the inactive isoform of p21 recovered from Sf9 cells treated with phosphatase inhibitors had been phosphorylated in vivo at Ser(146). These data identify the first phosphorylation site within the C-terminal regulatory domain of p21 whose modification in vivo modulates p21-PCNA interactions and define a eukaryotic cell model that can be used to study post-translational signaling pathways that regulate p21.

Amino Acid Sequence↗

Systemic mobilization of antigen presenting cells, with a chimeric Flt-3 and G-CSF receptor agonist, during immunization of Macaca mulatta with HIV-1 antigens is insufficient to modulate immune responses or vaccine efficacy.

In order to improve the efficacy of current vaccine candidates against HIV/AIDS, we sought to strengthen the induction of immune responses via simultaneous in vivo mobilization of dendritic cells using a chimeric Flt-3 and G-CSF receptor agonists (ProGP). We investigated ProGP treatment in combination with two DNA immunizations encoding HIV-Env89.6, SIV-Gag proteins to increase the priming of immune responses. Administration of this Flt-3/G-CSF chimera elicited marked increases in numbers of both plasmacytoid and myeloid dendritic cells. However, there was no increase seen in T-cell responses either directly following the DNA immunization or after further boosting with MVA vectors expressing HIV-Env89.6p, SIV-Gag. After challenge with SHIV89.6p all animals became infected and no differences were seen between the ProGP treated versus the control group with regard to plasma virus load or CD4 T-cell count. We conclude that besides mobilization of dendritic cells additional stimuli to induce dendritic cell maturation may be needed for avid boosting of antigen specific immune activation.

AIDS Vaccines↗

Vitamin A and immune function: retinoic acid modulates population dynamics in antigen receptor and CD38-stimulated splenic B cells.

Vitamin A and its active metabolite, all-trans retinoic acid (RA), regulate the antibody response in vivo, although the underlying mechanisms are not well understood. We have investigated the regulation by RA of B cell population dynamics and Ig gene expression in purified splenic mouse B cells stimulated through the B cell antigen receptor (BCR) and/or CD38, a BCR coreceptor. After ligation of the BCR and/or CD38, B cells became more heterogeneous in size. RA substantially restrained this change, concomitant with inhibition of cell proliferation. To examine B cell heterogeneity more closely, we categorized stimulated B cells by size (forward angle light scatter) and determined cell division dynamics, germ-line Ig heavy chain gene transcription and surface IgG1 (sIgG1) expression. Flow cytometric analysis of carboxyfluorescein diacetate succinimidyl ester-labeled B cells costained for sIgG1 showed that the more proliferative groups of B cells were smaller, whereas cells expressing more sIgG1 were larger. RA enriched the latter population, whereas cell division frequency in general and the number of smaller B cells that had undergone division cycles were reduced. Although RA significantly inhibited Ig germ-line transcript levels in the total B cell population, CD19(-)IgG1(+) B cells, which represent a more differentiated phenotype, were enriched. Furthermore, pax-5 mRNA was decreased and activation-induced cytidine deaminase mRNA was increased in RA-treated stimulated B cells. Thus, RA regulated factors known to be required for Ig class switch recombination and modulated the population dynamics of ligation-stimulated B cells, while promoting the progression of a fraction of B cells into differentiated sIgG-expressing cells.

ADP-ribosyl Cyclase 1↗

Involvement of multiple protein kinases in CD3-mediated activation of human T lymphocytes.

The role of different protein kinases in the process of T cell activation has been studied using several inhibitors. The model we adopted was the activation of PBMC by monoclonal antibody OKT3. The results obtained confirm that PKC and PTK are involved. Thus, the inhibitors H-7, staurosporine, and genistein exerted a dose-dependent inhibition of CD2 up-regulation, CD25 expression, IL-2 production, and cellular proliferation. On the other hand, our data indicate that PKA is not involved since the inhibitor HA1004 was ineffective. W-7, an inhibitor of Ca(2+)-CaM protein kinases, inhibited OKT3-induced modulation of cell-surface markers and PBMC proliferation, whereas a slight increase in IL-2 release was detected at the highest dose used (20 microM). Using the MLCK inhibitor ML-9, we extended our studies to the myosin light chain kinase, which influences the organization of the cytoskeleton. ML-9-inhibited PBMC activation in terms of modulation of cell-surface markers and proliferation but stimulated IL-2 production. Similar results were obtained using the cytoskeleton disruptors demecolcine and cytochalasin B. Taken together the data described herein indicate that T cell activation is a complex event in which, aside from classical signal transduction-associated kinases PKC and PTK, at least two other kinases, Ca(2+)-CaM kinases and MLCK, seem to be involved, the latter probably through correct assembly of the cytoskeleton.

Antigenic Modulation↗

Antigen processing: approaches for dissecting subcellular mechanisms that form the basis for T-cell responses modulating allergic reactions.

Antigen processing determines the production of peptides from antigens, including allergens, and their binding to class II major histocompatibility complex (MHC-II) molecules, which stimulate T-cell responses. Our studies have addressed the cell biology and biochemistry of the MHC-II antigen processing pathway using subcellular fractionation of macrophages on Percoll density gradients, coupled with other techniques. We have isolated a high density, late endocytic antigen processing compartment, with lysosomal properties, that contains a high level of MHC-II molecules, as assessed by several techniques. Moreover, the direct formation of peptide MHC-II complexes was demonstrated within this compartment, using a T hybridoma assay for peptide MHC-II complexes present in subcellular fractions of macrophages previously exposed to the model antigen, hen's egg-white lysozyme. These observations support an important role for this compartment in the class II major histocompatibility complex antigen processing pathway.

Animals↗

Bone marrow stroma-dependent modulation of CD45R isoform expression on Abelson virus transformed pre-B cells.

The CD45 glycoprotein family exhibits cell-lineage-associated structural heterogeneity which is due, in part, to alternative pre-mRNA splicing. The Abelson murine leukemia (A-MuLV) preferentially transforms immature B cells that express a B-cell-specific high molecular weight CD45 isoform, called B220. However, we observed that A-MuLV-transformed cell lines are often B220- while maintaining high levels of "pan" CD45 expression. In vitro transformation of murine bone marrow revealed that the stromal microenvironment over which A-MuLV-transformed lymphoblasts are grown affected the B220 phenotype of the pre-B cells. Over a period of a few weeks, B220+ populations grown over a clonal stromal cell line gradually became B220-. However, the transition from a B220+ to B220- phenotype was dependent on the lot of fetal calf serum used. In contrast, cells grown over a heterogeneous bone marrow stroma maintained B220+ expression for long periods of time. The appearance of B220- cells in clonal B220+ populations indicated that the change in phenotype resulted in part from modulation of B220 expression. B220- B-cell lines did not express the high molecular weight CD45 RNA species indicating that the B220- phenotype was due to alternative pre-mRNA splicing. Finally, the shift from B220+ to B220- was not accompanied by changes in the stage of development of the cultures. These observations demonstrate that expression of B220 is not required for the continued proliferation of Abelson-transformed pre-B cells and is regulated by unknown environmental factors.

Abelson murine leukemia virus↗

[Expression of vascular cell adhesion molecule-1 in lung slices from antigen sensitized rats and pharmacological modulation].

OBJECTIVE: To investigate the expression of vascular cell adhesion molecule-1(VCAM-1) in lung slices from antigen -sensitized rats and the modulation by drugs. METHODS: In isolated lung slices from ovalbumin(OVA)-sensitized rats, the relative expression of VCAM-1 was determined after drug treatment and OVA challenge. RESULT: The expression of VCAM-1 was enhanced in the sensitized rat lungs,and OVA challenge did not further increase the expression. Glycocorticosteroid dexamethasone and leukotriene cysLT receptor antagonist ONO-1078 inhibited the expression,but tachykinin NK-1 receptor antagonist SR-140333 had no such effect. CONCLUSION: VCAM-1 expression is enhanced in the sensitized rat lungs, and antigen challenge does not further up regulate the expression. Anti-inflammatory drugs have different effects on VCAM-1 expression. Dexamethasone and ONO-1078, but not SR-140333, can inhibit the expression.

Animals↗

Cytotoxic T lymphocyte antigen-4-dependent down-modulation of costimulatory molecules on dendritic cells in CD4+ CD25+ regulatory T-cell-mediated suppression.

We have previously demonstrated that CD4+ CD25+ natural regulatory T cells (Treg cells) induce down-modulation of CD80 and CD86 (B7) molecules on dendritic cells (DCs) in vitro. In this report we show that the extent of down-modulation is functionally significant because Treg-cell conditioned DCs induced poor T-cell proliferation responses. Further, we report that down-modulation was induced rapidly and was inhibited by blocking cytotoxic T lymphocyte antigen-4 (CTLA-4), which is constitutively expressed by the Treg cells. Even though Treg cells have previously been reported to kill antigen-presenting cells, the down-modulation was not due to selective killing of DCs expressing high level of the costimulatory molecules. We propose that Treg cells down-modulate B7-molecules on DCs in a CTLA-4-dependent way, thereby enhancing suppression of T-cell activity.

Animals↗

Effects of cadmium and vanadium ions on antigen-induced signaling in CD4(+) T cells.

Heavy metal environmental pollutants modulate antigen-directed responses by T lymphocytes, but the molecular mechanisms by which certain metal ions exert their effects are only poorly understood. We tested the hypothesis that cadmium and vanadium ions alter antigen-induced T cell signal transduction pathways in CD4(+) T helper cells. We used CD4(+) primary T lymphocytes and splenic T cells from DO.11.10 T cell receptor transgenic mice. We determined the effects of cadmium chloride and sodium orthovanadate at concentrations that did not induce apoptotic cell death, but affected cytokine or proliferation responses to antigenic stimulation. We used electrophoretic mobility shift assays to measure effects of cadmium and vanadium ions on antigen-induced activation of the nuclear transcriptional regulator proteins, nuclear factor-kappaB, cyclic AMP response element binding protein, nuclear factor of activated T cells, and activator protein-1. Different signaling pathways lead to activation of these transcription factors. Our results suggest that the two heavy metal ions differentially affect signaling pathways. This knowledge will help in the development of molecular epidemiological assays.

Animals↗

1F7 (CD26): a marker of thymic maturation involved in the differential regulation of the CD3 and CD2 pathways of human thymocyte activation.

We have recently shown that solid-phase immobilization of anti-1F7 recognizing the 110-kDa CD26 Ag is comitogenic for human peripheral blood T cell activation via both the CD3 and CD2 pathways. We have also demonstrated that binding of anti-1F7 leads to the disappearance of CD26 surface expression, and this anti-1F7-induced modulation results in an increase in anti-CD3 or anti-CD2-mediated peripheral blood T cell activation. In this report, we extended these findings by examining the expression and functional relationship of 1F7 on the CD3 and CD2 pathways of activation of human thymocytes. We now demonstrated that most of the anti-1F7 reactivity is found on medullary thymocytes, the population of thymocytes expressing high level of CD3 (CD3H). We have also shown that binding of anti-1F7 can induce a decrease in CD26 surface expression, with no detectable effect on the surface expression of CD3 or CD2. Most importantly, we showed that solid-phase immobilization of anti-1F7 has a comitogenic effect on thymocyte activation induced by anti-CD3 but not anti-CD2. In addition, anti-1F7-induced modulation of CD26 results in an enhancement in CD3-mediated but not CD2-mediated human thymocyte activation. The observed functional effect of CD26 on the CD3/TCR pathway of activation is mainly restricted to mature thymocytes as distinguished by high surface expression of CD5, although CD26 is also functionally associated with the CD3/TCR pathway on cells expressing low level of CD5. Demonstrating that CD26 involvement in the regulation of human thymocyte activation is restricted mainly to the CD3 pathway, unlike its involvement with both the CD3 and CD2 pathways of mature peripheral blood T lymphocyte activation, our data hence suggested that CD26 may play a role in thymic differentiation and maturation via the differential engagement of the CD3 pathway.

Antibodies, Monoclonal↗

A novel autocrine pathway of tumor escape from immune recognition: melanoma cell lines produce a soluble protein that diminishes expression of the gene encoding the melanocyte lineage melan-A/MART-1 antigen through down-modulation of its promoter.

We have observed that malignant melanoma cells produce a soluble protein factor(s), which down-regulates melanocyte lineage Melan-A/MART-1 Ag expression by melanoma cells with concomitant loss of recognition by Melan-A/MART-1-specific T cells. This down-modulation of Melan-A/MART-1 expression, which we refer to as "Ag silencing," is mediated via its minimal promoter, whereas the promoter for the restricting Ag-presenting HLA-A2 molecule is not affected. Significantly, this Ag silencing is reversible, as removal of factor-containing supernatants from Melan-A/MART-1-expressing cells results in up-regulation of the promoter for the gene encoding this Ag, and renewed expression of the protein. We have evaluated over 20 known factors, none of which accounts for the Ag-silencing activity of the melanoma cell culture supernatants. The existence of this autocrine pathway provides an additional novel explanation for melanoma tumor progression in vivo in the presence of CTL specific for this melanocyte lineage Ag. These observations may have important implications for Melan-A/MART-1-specific CTL-mediated immunotherapy of melanoma tumors.

Antigens, Neoplasm↗