Biomedical subjects

M Maric

Publications and source records attributed to M Maric.

At least 19 recordsLinked to original sources

PubMed2001

Defective antigen processing in GILT-free mice.

Processing of proteins for major histocompatibility complex (MHC) class II-restricted presentation to CD4-positive T lymphocytes occurs after they are internalized by antigen-presenting cells (APCs). Antigenic proteins frequently contain disulfide bonds, and their reduction in the endocytic pathway facilitates processing. In humans, a gamma interferon-inducible lysosomal thiol reductase (GILT) is constitutively present in late endocytic compartments of APCs. Here, we identified the mouse homolog of GILT and generated a GILT knockout mouse. GILT facilitated the processing and presentation to antigen-specific T cells of protein antigens containing disulfide bonds. The response to hen egg lysozyme, a model antigen with a compact structure containing four disulfide bonds, was examined in detail.

Amino Acid Sequence↗

PubMed2001

Cathepsin S regulates the expression of cathepsin L and the turnover of gamma-interferon-inducible lysosomal thiol reductase in B lymphocytes.

Loading of antigenic peptide fragments on major histocompatibility complex class II molecules is essential for generation of CD4(+) T cell responses and occurs after cathepsin-mediated degradation of the invariant chain chaperone molecule. Cathepsins are expressed differentially in antigen presenting cells, and mice deficient in cathepsin S or cathepsin L exhibit severely impaired antigen presentation in peripheral lymphoid organs and the thymus, respectively. To determine whether these defects are due solely to the block in invariant chain cleavage, we used cathepsin-deficient B cells to examine the role of cathepsins S and B in the degradation of other molecules important in the class II presentation pathway. Our data indicate that neither cathepsin S nor B is critical for H-2M degradation or processing of precursor gamma-interferon-inducible lysosomal thiol reductase (GILT) to a mature thiol reductase, but suggest a role for cathepsin S in the turnover of mature GILT and in regulating levels of mature cathepsin L protein in B cells. Despite the presence of mature cathepsin L protein, no enzyme activity could be detected in B cells or dendritic cells. These experiments suggest a novel mechanism by which these functionally important enzymes may be regulated.

Animals↗

PubMed1999

Strong cytotoxic T lymphocyte responses to a macrophage inflammatory protein 1alpha-expressing tumor: linkage between inflammation and specific immunity.

Leukocyte infiltration is an important histological sign of resistance to tumors. However, it is unclear whether local inflammatory responses can promote specific antitumor immunity. Here we report that local expression of macrophage inflammatory protein 1alpha, which results in strong inflammation of leukocytes in tumors, leads to the induction of strong antitumor CTL responses. The induction of CTL effectors requires co-stimulatory molecules B7-1 and/or B7-2 on host antigen-presenting cells but not on the tumors. These results establish a critical linkage between inflammation and specific immunity.

Animals↗

PubMed1999

Thiol oxidation and reduction in MHC-restricted antigen processing and presentation.

Major histocompatibility complex (MHC) class I molecules are assembled in the endoplasmic reticulum (ER) as a trimer of the class I heavy chain, beta2 microglobulin (beta2m), and a short peptide. Assembly occurs in a complex with additional noncovalently associated proteins, which include the thiol oxidoreductase, ERp57. This molecule facilitates the formation of the correct disulfide bonds in glycoproteins as they fold in the ER and may play a key role in assembling a stable MHC class I-peptide complex. In the endocytic pathway, reduction of protein disulfide bonds is important for the generation of MHC class II-peptide complexes. This process is catalyzed by a gamma-interferon-inducible thiol reductase (GILT). The possible requirement for catalysis of disulfide bond formation in MHC class I-restricted antigen processing and the known requirement for disulfide bond reduction in MHC class II-restricted antigen processing present interesting examples of the adaptation of cellular "housekeeping" functions to facilitate immune responses.

Animals↗

PubMed1998

Maturation of cytotoxic T lymphocytes against a B7-transfected nonmetastatic tumor: a critical role for costimulation by B7 on both tumor and host antigen-presenting cells.

It is generally believed that CTLs mature in lymphoid organs and then migrate into target tissues to execute their effector functions. This notion, however, is based on studies using antigens that are readily localized in the lymphoid tissue, such as viruses and allogeneic transplants. The site for maturation of CTLs for nonmetastatic tumors has not been determined. Because nonmetastatic tumor cells are not localized in lymphoid tissues, it is questionable whether such tumors are efficient inducers of antitumor CTLs. Here, we report that a nonmetastatic B7+ plasmacytoma induces strong effector CTL response. Thus, it is possible to induce CTLs with strong ex vivo CTL activity in the absence of tumor metastasis. In addition, a detailed kinetic analysis of CD8 T cell recruitment and maturation of CTL activity suggests that antitumor CTLs mature within the tumor rather than in the lymphoid tissues. Interestingly, despite B7-1 expression on tumor cells, induction of effector CTLs also requires costimulation by B7 on host antigen-presenting cells. These findings have important implications for tumor gene therapy and for understanding the mechanism of CTL induction in vivo.

Animals↗

PubMed1997

A mechanism for selective recruitment of CD8 T cells into B7-1-transfected plasmacytoma: role of macrophage-inflammatory protein 1alpha.

An important aspect of immunity is the recruitment and accumulation of lymphocytes into target tissues where Ags are localized. Because the TCR recognizes antigenic peptides presented by MHC molecules, the subset of T cells that exert effector function is determined by the class of MHC molecules expressed on a given tissue. We and others have demonstrated that CD8 T cells are preferentially recruited into B7-1-transfected class II-negative plasmacytoma J558, and the virus-infected central nervous system. However, the mechanism for such specificity has not been addressed. Here we analyzed the mechanism for selective recruitment of CD8 T cells into B7-1-transfected plasmacytoma J558. We show that sustained accumulation of CD8 T cells in vivo requires local expression of B7-1. In addition, we have observed a striking correlation between expression of macrophage-inflammatory protein 1alpha (MIP1alpha) and selective accumulation of CD8 T cells in the tumors. The selective recruitment of CD8 T cells is blocked by in vivo administration of neutralizing anti-MIP1alpha antisera. Moreover, gene-transfer studies reveal that locally produced MIP1alpha is sufficient to induce selective recruitment of CD8 T cells. Taken together, our study reveals that costimulation by B7 leads to sustained local production of MIP1alpha, which selectively recruits CD8 T cells into tumors. These results have important implications for T cell recruitment in vivo and for tumor immunotherapy.

Animals↗

PubMed1997

Improvement in cholestasis-associated fatigue with a serotonin receptor agonist using a novel rat model of fatigue assessment.

Fatigue is a common complaint in patients with liver disease; however, the etiology of fatigue is poorly understood and no therapeutic options are available to treat it. Altered central neurotransmission, especially serotonergic, appears to play a role in the genesis of fatigue. In this study, we describe a rat model of fatigue assessment using a swim tank, and we used this model to document the degree of fatigue in rat models of cholestasis caused by bile duct resection (BDR) and of hepatitis caused by carbon tetrachloride (CCl4) administration. Fatigue was quantitated as the time spent floating and struggling over a 15-minute period after placement in the swim tank, and an overall activity score was calculated. Using this technique, BDR rats exhibited significantly enhanced floating times and an overall reduction in activity score compared with noncholestatic controls (P < or = .01). On the other hand, CCl4-treated rats showed a marked variability in floating and struggling times and activity scores such that, overall, CCl4-treated rats were not significantly different from normal controls. Therefore, we used BDR and noncholestatic control rats to examine the effects of a serotonin (5HT1A) receptor agonist (LY293284) on cholestasis-associated fatigue. BDR rats treated with LY293284 (0.3 mg/kg subcutaneously 24, 5, and 1 hour before placement in the swim tank) showed marked reductions in floating times and an increase in overall activity scores compared with BDR controls (P < or = .001). LY293284 was without effect in noncholestatic animals. These results suggest that fatigue can be quantitated in rat models of liver disease and that 5HT1A receptor agonists may provide a useful therapeutic tool in the treatment of cholestatic liver disease-associated fatigue.

Animals↗

PubMed1997

TNF-alpha facilitates inflammation-induced glucocorticoid secretion in rats with biliary obstruction.

AIMS: We investigated the role of TNF-alpha in inflammation-induced activation of the hypothalamic-pituitary-adrenal (HPA) axis in rats with cholestasis due to bile duct resection. METHODS: Acute inflammation was induced in bile duct or sham resected rats by subcutaneous injection of carrageenan and HPA axis activation was determined by measuring plasma ACTH and corticosterone levels in the absence or presence of TNF-alpha inhibition. RESULTS: Bile duct resected rats had a 2.4-fold elevation in basal circulating TNF-alpha levels compared to sham resected and unoperated controls. Acute inflammation induced by carrageenan injection resulted in a significant increase in plasma ACTH and corticosterone levels in bile duct resected and control rats in the absence of significant changes in plasma TNF-alpha levels. However, bile duct resected rats demonstrated blunted ACTH release coupled with augmented corticosterone secretion in response to carrageenan administration compared to control rats. Inhibition of TNF-alpha activity by pretreating rats with a specific TNF-antiserum or pentoxifylline did not alter inflammation-induced ACTH secretion in bile duct resected or control rats, or corticosterone secretion in control rats. However, anti-TNF treatments significantly attenuated the inflammation-induced rise in plasma corticosterone in bile duct resected rats. CONCLUSIONS: These results indicate that inflammation in rats with biliary obstruction is associated with blunted ACTH release coupled with augmented glucocorticoid secretion facilitated by TNF-alpha. Furthermore, these results suggest that what have been previously considered as low level elevations in circulating TNF-alpha levels can facilitate adrenal glucocorticoid secretion during the inflammatory response.

Adrenocorticotropic Hormone↗

PubMed1996

Impaired stress and interleukin-1beta--induced hypothalamic expression of the neuronal activation marker FOS in cholestatic rats.

Both interleukin (IL)-1beta and psychological stress activate the hypothalamic-pituitary-adrenal (HPA) axis by stimulating neuronal activity within the paraventricular nucleus of the hypothalamus via different pathways. Because it has been shown previously that cholestatic rats show defective cytokine- and stress-induced HPA axis activation, neuronal activation in the paraventricular nucleus of rats with cholestasis caused by bile duct resection and in noncholestatic sham-resected (sham) controls was examined. To do this, the expression of the neuronal activation marker FOS in the hypothalamic paraventricular nucleus of bile duct-resected (BDR) and sham rats exposed to restraint stress and intracerebroventricularly infused IL-1beta, two stimuli known to activate the HPA axis by stimulating neurons in the paraventricular nucleus, was quantitated. BDR rats showed decreased FOS expression in the paraventricular nucleus after both stimuli compared with similarly treated sham controls. These data show that BDR rats show an impaired ability to activate hypothalamic neurons within the paraventricular nucleus and suggest that hypofunctioning of the HPA axis in response to immune (i.e., IL-1beta) and psychological stressors, which have been documented previously for BDR rats, may be caused by a specific defect in the intracellular machinery involved in the activation of neurons within the hypothalamic paraventricular nucleus.

Animals↗

PubMed1996

Tumor necrosis factor-alpha stimulates adrenal glucocorticoid secretion in cholestatic rats.

Tumor necrosis factor-alpha (TNF-alpha ) is capable of activating the hypothalamic-pituitary-adrenal (HPA) axis. We have recently documented altered activation of this axis by endotoxin and interleukin-1 in cholestatic rats. Therefore, in this study, we examined TNF-alpha-induced activation of the HPA axis, in rats with cholestasis due to bile duct resection, with the use of sham-resected rats as controls. Administration of TNF-alpha to bile duct- and sham-resected rats in vivo resulted in a similar increase in plasma adrenocorticotropic hormone levels in both groups of animals but significantly higher corticosterone levels in cholestatic rats, suggesting a direct steroidogenic effect of TNF-alpha in cholestatic rats. This suggestion was confirmed in further experiments by the demonstration of TNF-alpha-induced corticosterone secretion in hypophysectomized cholestatic but not control rats. Furthermore, a direct stimulatory effect of TNF-alpha on adrenal corticosterone secretion in vitro was noted only for cholestatic rats, possibly via augmented adrenal prostaglandin E2 (PGE2) production. These results indicate that TNF-alpha has a direct stimulatory effect on adrenal corticosterone secretion in cholestatic rats, possibly due to augmented adrenal PGE2 release.

Adrenal Glands↗

PubMed1995

Multiple lineages of tumors express a common tumor antigen, P1A, but they are not cross-protected.

Whether tumors of different lineages share common Ags is a critical issue for understanding anti-tumor immune responses and for designing Ag-specific tumor immunotherapy. Because of lack of cross-protection among individually derived tumors, it has been proposed that tumor Ags are specific for individual tumors. Here we show that lack of cross-protection is not due to lack of a shared tumor Ag. Thus, a plasmocytoma J558 transfected with the costimulatory molecule B7 activates a cross-reactive CTL response in vivo. The major Ag recognized by the cross-reactive CTL is P1A, which is expressed in mastocytoma P815, plasmocytoma J558, and fibrosarcoma Meth A. Surprisingly, no significant cross-protection can be detected among P1A-expressing tumors after immunization with either P1A-expressing or B7-transfected P815 cells. Our results demonstrate that multiple lineages of tumors are not cross-protected even though they share a tumor Ag that can be recognized by CTL. These results have important implications for tumor immunotherapy.

Amino Acid Sequence↗

PubMed1995

Defective interleukin-1-induced ACTH release in cholestatic rats: impaired hypothalamic PGE2 release.

A complete regulatory loop exists between the immune and neuroendocrine systems. Proinflammatory mediators such as endotoxin (lipopolysaccharide) and interleukin-1 (IL-1) are capable of activating the hypothalamic-pituitary-adrenal (HPA) axis at the hypothalamic level, presumably by inducing the synthesis of prostaglandins. We have recently identified abnormalities in the stress-induced activation of the HPA axis in cholestatic rats. Therefore, in rats with cholestasis due to bile duct resection and sham-resected controls, we studied alterations in proinflammatory mediator-induced activation of the HPA axis and documented the role of alterations in hypothalamic prostaglandin synthesis in these abnormalities. Systemic administration of endotoxin and IL-1 resulted in a significant attenuation of adrenocorticotropic hormone (ACTH) release into plasma in bile duct-resected compared with sham-resected animals. This suppression of endotoxin- or IL-1-induced ACTH release in bile duct-resected rats was associated with a complete absence of IL-1-induced hypothalamic release of prostaglandin E2 (PGE2) in vitro in these animals. In contrast, sham-resected rats exhibited a 70% increase in hypothalamic PGE2 secretion in vitro in response to IL-1. However, bile duct-resected rats exhibited HPA axis activation similar to that of sham-resected animals in response to intracerebroventricularly infused PGE2. Therefore, cholestasis in the rat is associated with an attenuation of central activation of the HPA axis by proinflammatory mediators that appears to be mediated, at least in part, by defective IL-1-induced hypothalamic prostaglandin production.

Adrenocorticotropic Hormone↗

PubMed1995

Defective corticotropin-releasing hormone mediated neuroendocrine and behavioral responses in cholestatic rats: implications for cholestatic liver disease-related sickness behaviors.

Nonspecific systemic complaints are commonly encountered in patients with cholestatic liver diseases. However, the cause of these symptoms is poorly understood. Because corticotropin-releasing hormone (CRH) has been implicated as a mediator of sickness-related systemic symptoms, we examined CRH-mediated neuroendocrine and behavioral responses in rats with cholestasis due to bile duct resection (BDR) or sham resected (sham) controls. BDR and sham rats were placed individually in an open field apparatus, and the number of inner and outer squares entered, as well as the number of fecal boli produced, counted over a 5-minute period. Fecal boli production and inner squares entered are dependent on central CRH release. BDR and sham rats entered the same number of outer squares; however, BDR rats entered significantly fewer inner squares and produced fewer fecal boli than did sham rats, suggesting defective central CRH release in BDR rats. Immediately after exposure to the open field, rats were killed and blood adrenocorticotropic hormone (ACTH) levels measured. ACTH release is dependent on central CRH release. BDR rats demonstrated significantly lower plasma ACTH levels after exposure to an open field than did sham animals. To further explore the central CRH defect in BDR rats, hypothalamic CRH contents were determined in BDR and sham rats with and without exposure to restraint stress. BDR rats had significantly lower basal hypothalamic CRH levels than sham animals, and CRH levels did not further decrease in BDR rats with restraint stress (as normally occurs). These results are consistent with defective CRH-mediated responses in cholestatic rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗

PubMed1994

Prevention of immune-mediated arthritis in cholestatic rats: involvement of endogenous glucocorticoids.

BACKGROUND/AIMS: Hyporesponsiveness of the hypothalamic-pituitary-adrenal axis to stress is implicated in the development of immune-mediated arthritis in rats. This study investigated whether the documented hyporesponsiveness of the hypothalamic-pituitary-adrenal axis in cholestatic rats predisposes them to immune-mediated arthritis. METHODS: Bile duct-resected (BDR) and sham-resected rats were injected with either complete Freund's adjuvant (CFA; to induce immune-mediated arthritis) or incomplete Freund's adjuvant (IFA) at the time of laparotomy. Arthritis development was then assessed using a clinical arthritis score, and plasma corticosterone levels were determined. RESULTS: CFA-injected sham-resected rats developed arthritis, whereas CFA-injected BDR rats did not. CFA- and IFA-injected BDR rats had 14- and 6-fold higher levels of plasma free corticosterone than respective sham-resected controls. In addition, CFA-injected BDR rats treated with the glucocorticoid receptor antagonist RU 486 developed severe arthritis. CONCLUSIONS: Cholestasis because of BDR prevents the occurrence of immune-mediated arthritis and is associated with elevated plasma free corticosterone levels. Furthermore, CFA-injected BDR rats treated with RU 486 developed severe arthritis. Therefore, high-circulating glucocorticoid levels seem to result in a relative state of immunosuppression in BDR rats.

Analysis of Variance↗

PubMed1994

Intracellular assembly and transport of endogenous peptide-MHC class II complexes.

To define the intracellular site of assembly of endogenous peptide-MHC class II complexes, an immunochemical approach was undertaken employing a monoclonal antibody specific for an endogenous peptide-class II complex in combination with subcellular fractionation. Here, we show that newly synthesized MHC class II molecules, upon exit from the Golgi, are delivered into a dense endocytic compartment (MIIC) distinct from late endosomes and lysosomes. Endogenous peptide-class II complexes are initially formed in this compartment and subsequently traffic through late endosomal vesicles prior to cell surface expression. Exogenous antigen delivered via immunoglobulin receptors is targeted to MIIC en route to lysosomes after passing through early and late endosomes. Processing of an endocytosed antigen was observed in this compartment. Our results suggest a specific role for MIIC in the processing of endogenous and exogenous proteins as well as the assembly of peptide-MHC class II complexes.

Animals↗

PubMed1993

Mediation of anaphylaxis-induced jejunal circular smooth muscle contraction in rats.

Altered intestinal motility and diarrhea are features of food protein-induced intestinal anaphylaxis in the conscious rat. These experiments were performed to determine the mediator(s) responsible for jejunal circular smooth muscle contraction during this response. Hooded-Lister rats were sensitized by intraperitoneal injection of 10-micrograms egg albumin, and controls were sham-sensitized with saline. Fourteen days later the contractility of the circular muscle in jejunal segments (mucosa intact) was examined in standard tissue baths in response to antigen (Ag) or other agents. While control and sensitized tissues contracted in similar fashion in response to stretch, bethanechol, histamine, or 5-hydroxytryptamine (5HT), Ag contracted only the segments of sensitized animals. The contractile response was: (1) specific to the sensitizing Ag, as bovine serum albumin did not induce contraction and (2) could be passively transferred with serum containing specific immunoglobulin E antibody (IgE-Ab). Concanavalin A, which degranulates both mucosal and connective tissue-type mast cells, and compound 48/80, which degranulates only connective tissue-type mast cells produced contractile responses. Ag-induced contraction was significantly inhibited by the mucosal and connective tissue-type mast cell stabilizer doxantrazole, but not the connective tissue mast cell stabilizer disodium cromoglycate. Diphenhydramine and cimetidine together significantly inhibited histamine-induced contraction, but failed to effect the Ag-induced contraction in sensitized tissues. While the contractile response to 5HT was reduced in the presence of methysergide (5HT1-receptor antagonist), cinanserin (5HT2-receptor antagonist), and ICS 205-930 (5HT3-receptor antagonist), only cinanserin significantly inhibited the contractile response to Ag. Indomethacin significantly inhibited Ag-induced contraction. Ag-induced contraction was resistant to atropine and tetrodotoxin.(ABSTRACT TRUNCATED AT 250 WORDS)

Anaphylaxis↗

PubMed1991

A limited role for leukotrienes and platelet-activating factor in food protein induced jejunal smooth muscle contraction in sensitized rats.

To determine whether the release of newly formed mediators such as the peptidoleukotrienes and platelet-activating factor might modulate the food protein induced jejunal smooth muscle contraction observed in sensitized rats, Hooded-Lister rats were sensitized by injection of ovalbumin (10 micrograms i.p.) and controls were sham sensitized with saline. Fourteen days later the contractility of longitudinally (n = 9) and circularly (n = 9) oriented jejunal segments (mucosa intact) were examined in standard tissue baths in response to antigen, leukotrienes, and platelet-activating factor alone and in the presence of a specific leukotriene receptor antagonist (MK-571), a 5-lipoxygenase inhibitor (L651,392), and a platelet-activating factor receptor antagonist (WEB 2086). Although the responses of control and sensitized tissues to stretch and 10(-4) M bethanechol were similar, only sensitized tissues contracted in response to antigen (1 mg/mL). MK-571 (10(-5) M) reduced or significantly inhibited the contractile response of sensitized longitudinally and circularly oriented tissues to 10(-7) M leukotrienes C4, D4, or E4, but neither L651,392 (10(-4) M) nor MK-571 (10(-5) M) significantly reduced the contractile response of sensitized tissues to antigen challenge. WEB 2086 (10(-4) M) significantly (p less than 0.01) reduced the contractile response of sensitized longitudinally and circularly oriented tissues to 10(-7) M platelet-activating factor but did not significantly alter the response to antigen in longitudinally (45% of control, p = 0.14) or circularly (118% of control, ns) oriented jejunal smooth muscle. In this model leukotrienes and platelet-activating factor play an insignificant role in modulating food protein induced jejunal smooth muscle contraction in intestinal anaphylaxis.

Anaphylaxis↗

PubMed1990

Mediation of food protein-induced jejunal smooth muscle contraction in sensitized rats.

Alterations in myoelectric and motor activity are important features of food protein-induced intestinal anaphylaxis. To determine the mediator(s) involved, rats were sensitized by injection of egg albumin (10 micrograms ip), and controls were sham sensitized with saline. Fourteen days later the contractility of longitudinally oriented jejunal segments (mucosa intact) was examined in standard tissue baths in response to antigen (Ag) or other agents. Although control and sensitized tissues similarly contracted to stretch, bethanechol, histamine, or 5-hydroxytryptamine (5-HT), Ag contracted only sensitized segments. Contractile response 1) was specific to the sensitizing Ag, as bovine serum albumin did not induce contraction, and 2) could be passively transferred with serum containing specific IgE antibody. Mast cell degranulation after Ag challenge was suggested by a significant loss of granulated mast cells in sensitized compared with control rats challenged with Ag. Concanavalin A, which degranulates mucosal and connective tissue-type mast cells, and compound 48/80, which degranulates only connective tissue-type mast cells, produced a contractile response. Ag-induced contraction was significantly inhibited by the mucosal and connective tissue-type mast cell stabilizer doxantrazole (P less than 0.001) and the connective tissue mast cell stabilizer disodium cromoglycate (P less than 0.05). Diphenhydramine and cimetidine together blocked histamine-induced contraction but failed to affect Ag-induced contraction in sensitized tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗