Rapid transepithelial antigen transport in rat jejunum: impact of sensitization and the hypersensitivity reaction

BACKGROUND & AIMS: Intestine from sensitized rats develops a rapid secretory response to luminal antigen challenge that depends on activation of subepithelial mast cells. The aim of this study was to determine the timing and route of the transepithelial protein antigen transport. METHODS: Rats were sensitized to horseradish peroxidase (HRP). After 10-14 days, jejunal segments were resected, mounted in Ussing chambers, and challenged with HRP on the luminal side. RESULTS: Electron microscopy of tissue specimens fixed at 2 minutes (before mast cell activation) showed enhanced endocytic uptake of HRP in enterocytes of HRP-sensitized rats compared with ovalbumin-sensitized or saline-injected controls. At this time, HRP was distributed throughout epithelial cells and was already evident in the lamina propria. In contrast, HRP was restricted to the apical region of enterocytes in controls. At 30 minutes (after mast cell activation), in HRP-sensitized rats only, HRP was also located within tight junctions and the paracellular region between epithelial cells. Tissue conductance was increased in HRP-sensitized rats beginning 30 minutes after HRP addition and correlated with the overall flux of HRP across the tissue. CONCLUSIONS: The results show that specific sensitization enhances the initial uptake and transcytosis of antigen across intestinal epithelium. Subsequent to activation of mast cells, antigen transport is further enhanced by penetration through the paracellular pathway.     

Geographic epidemiology of gonorrhea in Baltimore, Maryland, using a geographic information system

Ws/Ws rats are deficient in both mucosal- and connective tissue-type mast cells. To study the role of mast cells in active anaphylaxis, changes in vascular permeability in the trachea upon intravenous antigen challenge with Evans blue dye were examined in Ws/Ws, heterogenic Ws/+, and normal +/ + rats sensitized with the nematode Nippostrongylus brasiliensis. Antigen challenge resulted in fatal anaphylactic shock in some +/+ and Ws/+ rats, but not in Ws/Ws rats. Marked dye leakage developed within 30 min in the trachea of +/+ and Ws/+ rats, while Ws/Ws rats showed no substantial increases in the levels of vascular permeability. Ex vivo stimulation of sensitized lung fragments from +/+ animals with specific antigen induced significant releases of histamine and leukotriene (LT) C4, while sensitized Ws/Ws rat-lung fragments did not. In Ws/Ws rats, levels of nematode-specific IgE, IgG1 and IgG2a antibodies as well as levels of lung eosinophilia were not significantly different from those in +/+ rats. These results show that mast cell-deficient Ws/Ws rats fail to develop active anaphylaxis, and this is mediated probably by the lack of mast cell-derived mediators required for initiation of the reaction.     

Disturbed pyloric motility in Ws/Ws mutant rats due to deficiency of c-kit-expressing interstitial cells of Cajal

Interstitial cells of Cajal (ICC) are believed to initiate the basic contractile activity of the gastrointestinal tract. Interstitial cells of Cajal express c-kit receptor tyrosine kinase and are deficient in Ws/Ws mutant rats with a small deletion of the c-kit gene. As Ws/Ws rats show remarkable bile reflux to the stomach, the contraction pressure of the pylorus was compared between Ws/Ws and control +/+ rats. The contraction pressure of the pylorus was measured using a microtransducer, which was inserted through a pin-hole in the anterior wall of the stomach under anesthesia. The magnitude of bile reflux was estimated by measuring the content of bile acids in the stomach. The c-kit messenger RNA-expressing cells were detected by in situ hybridization. Frequency and the maximum pressure of the contraction were comparable between Ws/Ws and +/+ rats, but the duration of the contraction was significantly shorter in Ws/Ws rats than in +/+ rats. The number of c-kit messenger RNA-expressing ICC in the pylorus of Ws/Ws rats was 1.7% that of +/+ rats. The bile reflux observed in Ws/Ws rats was attributed to the decrease in the duration of the pyloric contraction, which appeared to result from the deficiency of c-kit messenger RNA-expressing ICC.     

Suppression of inward-rectifying K+ channels KAT1 and AKT2 by dominant negative point mutations in the KAT1 alpha-subunit

Na(+)-glucose transport and transepithelial permeability were investigated during symptomatic acute cryptosporidiosis in newborn rats. The infection resulted in a significant (P < 0.01) decrease in the ileal short-circuit current and a nonsignificant fall in the transepithelial potential difference and conductance. In glucose-stimulated conditions, the rise in ileal short-circuit current and transepithelial permeability were significantly lower in Cryptosporidium parvum-infected rats than in controls (delta Isc = 3.24 +/- 1.21 microA.cm-2 vs delta Isc = 5.09 +/- 2.23 microA.cm-2 in infected and control animals, respectively; P < 0.001; delta PD = -0.35 +/- 0.13 mV vs delta PD = -0.44 +/- 0.14 mV for infected and control animals, respectively; P < 0.01). Electrical parameters were not affected by addition of the cyclooxygenase inhibitor indomethacin in either Cryptosporidium-infected newborn rats or controls. Horseradish peroxidase and mannitol flux studies demonstrated a significant decrease (P < 0.05) in transepithelial molecular permeability in infected enterocyte rats, HRP flux = 380, range 68-5570 ng.cm-2, and mannitol flux = 1.06, range, 0.34-1.44%.cm-2.min-1, compared with controls rats, HRP flux = 4446 range, 1121-124,363 ng.cm-2, and mannitol flux = 1.99, range, 0.57-5.09%.cm-2.min-1; P < 0.05. These effects could originate from C. parvum-induced alteration of intracellular trafficking of pinocytosis vesicles and therefore account for the decrease in permeability to solute and macromolecules, together with impaired transcellular nutrient transport, in suckling rats.     

In vitro passive sensitization of the ureter as a basis for the study of noninfectious ureteral inflammation

PURPOSE: To develop an in vitro model of passive sensitization for the ureter for the study of noninfectious ureteral inflammation. MATERIALS AND METHODS: Human ureteral tissues were obtained from excess segments of ureters from patients undergoing donor nephrectomy. Following excision, ureters were placed in physiologic salt solution (PSS) and passively sensitized by incubating with ragweed serum from allergic donor (1 ml. serum: 4 ml. PSS) for 20 hours at room temperature. Ureteral segments were incubated with PSS only and served as non-sensitized controls (n = 4). After sensitization, excess serum was removed by serial washing with PSS without serum. Ureteral strips were then suspended in vitro for determination of tissue contraction. Contractile responses and histamine release were measured. Tissues were then exposed to antigen. To investigate the role of inflammatory mediators in tissue contraction, 4 groups of 8 sensitized ureteral segments were incubated for 1 hour with the following substances: a H1 histamine receptor antagonist (pyrilamine), an inhibitor of prostaglandin synthesis (indomethacin), an inhibitor of leukotriene synthesis (A-64077), and a control substance (DMSO). Following incubation, the tissues were exposed to antigen, and contraction and histamine release were determined. RESULTS: Sensitized ureteral segments (n = 8) responded to antigen with contraction (30% BaCl maximum; p <0.01) and histamine release (205/ng./gm. tissue) within the first 5 minutes of superfusion. Non-sensitized control segments (n = 4) did not respond. Both indomethacin and pyrilamine reduced (7-10% of BaCl maximum; p <0.05) the contractile response of sensitized ureter to antigen, whereas A-64077 did not. Analysis of the superfusate for histamine indicates that indomethacin reduced histamine release (150 ng./gm.) whereas A-64077 and pyrilamine did not (p <0.05). CONCLUSION: We have demonstrated that ureteral segments can be passively sensitized and that subsequent antigen challenge stimulates contraction and histamine release. Our findings suggest that contraction of ureteral tissue and histamine release may be utilized as an inherent bioassay indicating the activity of inflammatory mediators. In addition, these results suggest that both prostaglandins and histamine, but apparently not leukotrienes, participate in the early inflammatory response to antigen challenge of the sensitized ureter.     

IgE-induced passive sensitization of human isolated bronchi and lung mast cells

Passive sensitization of human isolated lung with serum from atopic asthmatic patients provides an opportunity to study the link between airway hyper-responsiveness and the allergic process. To directly demonstrate the role of immunoglobulin E (IgE) in the effect of the atopic serum, we have compared the effect of passively sensitizing both human bronchi and isolated lung mast cells with either serum from atopic asthmatic patients or human monoclonal IgE. Peripheral bronchi ( < 5 mm in internal diameter) were dissected out from human lung obtained at thoractomy and isometric contraction was studied in response to a variety of immunological stimuli according to the sensitization protocol. Mast cells were also isolated from human lung and histamine release was measured under similar experimental conditions. A contractile response was elicited by either the specific antigen or anti-IgE (0.6-600 ng.mL-1) but not anti-immunoglobulin G (IgG) 0.2-20 micrograms.mL-1) in airways sensitized with atopic serum (total IgE concentration of approximately 1,000 international units (IU).mL-1). The maximal contractile response to anti-IgE was 75 +/- 22% of the response to 1 mM acetylcholine. Similarly, anti-IgE released histamine from isolated lung mast cells sensitized with atopic serum up to 22.4 +/- 2% of total histamine measured within mast cells. When isolated airways or mast cells were sensitized with human monoclonal IgE (1,000 IU.mL-1), response to anti-IgE in terms of contractile response or histamine release, respectively, were not significantly different from those obtained following passive sensitization with atopic serum. Finally, the bronchial contractile response to anti-IgE depended not only on the concentration of anti-IgE but also on that of IgE (300-2,000 IU.mL-1) used to sensitize the airways. These results indicate that the effect of antigen or anti-IgE in peripheral bronchi passively sensitized with atopic serum is mimicked when sensitization is carried out directly with human monoclonal IgE.     

Poststorage diastolic abnormalities of heart transplants: is vascular dysfunction or myocardial contracture the culprit?

We tested the hypothesis that mast cells contribute to platelet-activating factor (PAF)-induced airways hyperreactivity and hyperpermeability in mice. Airways reactivity to acetylcholine (ACh) and lung permeability to Evans blue (EB) dye were measured before and after PAF challenge in genetically mast cell-deficient (WBB6F1 W/Wv) and normal congenic (WBB6F1 +/+) mice, as well as mast cell-reconstituted (BMT W/Wv) mice. In addition, prostaglandin D2 (PGD2), a mast cell-specific mediator, was measured in the bronchoalveolar lavage (BAL) from +/+ and W/Wv mice to determine if lung mast cell activation was a consequence of PAF challenge. Genetically PAF-sensitive AKR/J mice were also treated with the mast cell stabilizer nedocromil prior to assessment of PAF effects on ACh reactivity. Intravenous PAF (10 micrograms/kg) induced a significant (P < 0.05) increase in airways reactivity to ACh (25 micrograms/kg) in both +/+ (371 +/- 52%) and W/Wv (122 +/- 24%) mice. There was a significantly greater increase in +/+ compared with W/Wv mice. PAF-induced hyperreactivity to ACh in BMT W/Wv mice (191 +/- 44%) was significantly (P < 0.05) greater than age-matched W/Wv mice (80 +/- 16%), but not significantly different from age-matched +/+ mice (153 +/- 44%). PAF (10 micrograms/kg) also significantly (P < 0.5) increased lung permeability in +/+ and W/Wv mice, but there was no significant difference between groups. BAL PGD2 increased significantly in +/+ mice following PAF challenge (559 +/- 24 ng/ml) compared with vehicle controls (152 +/- 8 pg/ml). There was no significant increase in BAL PGD2 from W/Wv mice. Nedocromil pretreatment significantly (P < 0.05) decreased PAF-induced hyperreactivity in AKR/J mice but not in W/Wv mice (P > 0.05). We conclude that mast cells contribute significantly to PAF-induced hyperreactivity but not hyperpermeability in mice.     

Norepinephrine accelerates HIV replication via protein kinase A-dependent effects on cytokine production

In vivo, IgE production is related to bronchial hyperresponsiveness and, in vitro, passive sensitization of human airways with asthmatic serum containing a high concentration of IgE enhances the contractile response to a variety of agonists. However, cell types implicated in this IgE sensitization are not fully determined. The aim of this study was to determine IgE-bearing cells during passive sensitization with special reference to mast cells. Peripheral bronchi were dissected out from 10 lung specimens obtained at thoracotomy and processed into glycolmethacrylate resin. Sections, each 2 microm thick, were passively sensitized by incubation for 2 h at 37 degrees C in either buffer supplemented with monoclonal IgE or asthmatic serum with a high concentration of IgE (> or = 1,000 IU/ml). Immunohistochemistry was performed using monoclonal antibodies directed against the epsilon chain, and markers of the various IgE-bearing cells (e.g., AA1, antichymase). The number of IgE-bearing cells was significantly higher in passively sensitized specimens as compared with nonsensitized specimens (6.63 +/- 1.71 versus 4.29 +/- 1.35/mm2; p = 0.013, n = 10). Mast cells represented 65% of IgE-bearing cells, 41.6 and 23.4% for TC and T subtypes, respectively. These results indicate that mast cell is the main cell type involved in IgE-induced passive sensitization. The involvement of mast cell-derived tryptase in the mechanisms of IgE-related hyperresponsiveness should be further examined.     

Studies on the mechanisms involved in antigen-evoked pleural inflammation in rats: contribution of IgE and complement

Immunoglobulin E (IgE) has been shown to play a critical role in the allergic late-phase reaction, which is marked by intense leukocyte infiltration and edema. In this study we assessed the allergic pleural inflammation triggered by intrapleural (i.pl.) challenge in sensitized rats. We examined pleural effluent from actively sensitized rats following anti-IgE monoclonal antibody (mAb) (MARE-1) provocation for protein exudation, neutrophil as well as eosinophil accumulation. Inflammatory changes triggered by antigen after passive sensitization with IgE mAb was also assessed for comparison. Total serum level of IgE was found to be about threefold increased 7-8 days post-active sensitization, remaining augmented for at least 30 days. Increased levels of peritoneal leukocyte-bound IgE and serum IgE with specificity to ovalbumin were also detected. Nevertheless, the anti-IgE challenge in 14-day actively sensitized was shown to be a weak stimulus of neutrophil and eosinophil accumulation, despite being able to cause intense protein extravasation. Similarly, antigen challenge of IgE-passively sensitized rats caused protein leakage that was comparable to that induced by anti-IgE mAb in actively sensitized rats but led to a much lower neutrophil/eosinophil infiltration. Also, blockade of complement with recombinant human soluble C receptor-1 (sCR1) treatment prevented actively sensitized rats from reacting to antigen with neutrophil and eosinophil recruitment without modifying protein extravasation. These data suggest that IgE and complement-mediated mechanisms probably account for the exudation and leukocyte infiltration that is characteristic of the pleural inflammatory response observed in actively sensitized rats.     

Modulation of cocaine- and methamphetamine-induced behavioral sensitization by inhibition of brain nitric oxide synthase

Evidence suggests the existence of multiple interactions between dopamine, glutamate and nitric oxide (NO) in brain structures associated with psychomotor stimulation. The present study was undertaken to investigate the effect of the relatively selective inhibitor of the neuronal nitric oxide synthase (NOS) isoform, 7-nitroindazole (7-NI), on the development of sensitization to the locomotor stimulating effect of cocaine and methamphetamine (METH). Male Swiss Webster mice that received 15 mg/kg cocaine once a day for 5 days developed a marked locomotor sensitization to a challenge cocaine (15 mg/kg) or cross-sensitization to a challenge METH (0.5 mg/kg) injection given after a 10-day drug-free period. This treatment also produced a context-dependent sensitization as evident by the sensitized response to a challenge saline injection. Pretreatment with 7-NI (25 mg/kg) 30 min before cocaine administration (5 days) completely blocked the induction of sensitization to cocaine, the cross-sensitization to METH and the conditioned locomotion induced by cocaine. 7-NI when given alone, either acutely or for 5 days, had no significant effect on the locomotor activity of animals. Animals treated with METH (1.0 mg/kg) for 5 days developed marked sensitization to challenge METH (0.5 mg/kg), cross-sensitization to challenge cocaine (15 mg/kg) and context-dependent locomotion. Pretreatment with 7-NI (25 mg/kg) attenuated the sensitized response to METH and the cross-sensitization to cocaine as revealed after a 10-day drug-free period. However, the METH-induced conditioned locomotion was unaffected by the pretreatment with 7-NI. The present study supports the role of brain NO in the development of sensitization to both psychostimulants, cocaine and METH. However, it appears that the inability of 7-NI to completely abolish the sensitized responses induced after METH administration is the result of the resistible conditioned locomotion caused by METH, but not by cocaine.     

Detection and quantification of Epstein-Barr virus EBER1 in EBV-infected cells by fluorescent in situ hybridization and flow cytometry

BACKGROUND: The level of histamine in nasal lavage fluid has been used as an index of mast cell/basophil activation in a number of studies. Obviously, such an index can only be valid if changes in the secretory activity of nasal glands do not affect the level of histamine in lavage fluid (i.e. hypersecretion, without a simultaneous activation of mast cells/basophils in the nasal mucosa, must not increase the level of histamine). OBJECTIVES: To asses the effect of nasal hypersecretion on histamine levels in lavage fluid. METHODS: Nasal challenges were performed with methacholine and allergen in grass pollen-allergic patients and non-allergic controls. Nasal lavage fluid was collected before and repeatedly for nine hours after nasal challenge, and the level of histamine was compared with that of a specific mast cell-derived enzyme, tryptase. In addition, the effect of methacholine on basophils was examined in vitro. RESULTS: Allergen challenge of allergic patients produced sneezing and a significant increase in histamine and tryptase levels, whereas challenge of non-allergic subjects produced no such response. Interestingly, challenge with methacholine also induced a significant increase in histamine levels. This increase was seen in both allergic and non-allergic subjects and it was not associated with any sneezing or increase in tryptase levels, indicating that mast cells were not activated. Furthermore, stimulation of basophils with methacholine did not induce any histamine release in vitro. CONCLUSIONS: Apparently, there exists a pool of histamine in the human nose that can be transferred to lavage fluid during glandular hypersecretion. The source of this histamine is yet to be identified. As the level of histamine seems to be affected by the secretory activity of nasal glands, we question the use of this single mediator as an index of mast cell/basophil activation in nasal lavage studies.     

Expression of protein kinase C gene family members is temporally and spatially regulated during neural development in vitro

The dog mastocytoma BR cell line provides us with a permanent source of canine mast cells, allowing a characterization of secretory mediators that exert important effects in canine allergic and nonallergic diseases and in physiological processes. We studied the ultrastructural characteristics and histamine releasing activity after immunological and non-immunological stimuli of the dog mastocytoma BR cell line, and compared the cell line to normal skin mast cells enzymatically isolated from healthy dogs. The histamine content of BR cells was 0.04 +/- 0.002 pg/cell, approximately 100-fold less than that found in canine skin mast cells. Non-immunologic stimuli induced similar concentration-dependent histamine release from skin mast cells and BR cells: 29.3 +/- 0.9% vs. 12.7 +/- 0.7% (calcium ionophore A23187), 23.3 +/- 0.7% vs. 18.8 +/- 0.7% (substance P) and 12.5 +/- 0.3% vs. 12.1 +/- 0.9% (compound 48/80), respectively. Immunologic stimulation, however, was only effective on canine skin mast cells, causing 30.9 +/- 1.7%, 27.7 +/- 0.6% and 12.2 +/- 0.9% histamine release in response to anti-canine IgE, concanavalin A, and antigen Asc S 1, respectively. The absence of functional IgE receptors in BR cells was confirmed by the lack of response to anti-IgE and antigen Asc S 1 following passive sensitization with dog atopic serum and dog antigen sensitized serum. We conclude that BR cells are able to release histamine after non-immunologic stimulation in a similar manner to canine skin mast cells, but that there are morphological and functional differences possibly due to different states of maturity or differentiation. For this reason the study of the highly homogeneous BR cells could offer insights into dog mast cell biology in contexts where freshly isolated cells cannot be used because of low purity and recovery.     

In vivo and in vitro cellular response to Schistosoma japonicum eggs in hosts with differing susceptibilities

A comparative study of the cellular response to Schistosoma japonicum eggs was conducted in order to explore its significance, using hosts with differing susceptibilities to the parasite. In experimentally induced, synchronized hepatic granuloma formation, animal species formed each characteristic feature of the granulomas, and the magnitude of tissue reaction was significantly larger in highly susceptible hosts, such as mice and hamsters, while less susceptible hosts, such as rats and quails, formed smaller granulomas. Confluent neutrophils were seen within the tissue lesions for mice and hamsters, while rats and quails showed obviously scanty neutrophils. Guinea pigs failed to develop any granulomas. When splenic cells and bone marrow cells were used for in vitro granuloma formation, bone marrow cells showed markedly higher reactions than splenic cells from naive or sensitized animals and the reactivities of bone marrow cells from susceptible hosts, mice and hamsters, were clearly higher than those from rats, indicating similar results to those of in vivo granuloma formation. This study indicates that the in vivo and in vitro cellular response to S. japonicum eggs varies greatly according to the host's susceptibility, independent of whether the host is a naive or sensitized animal. Our results seem to support the concept that the parasites exploit the host immune system in order to complete their life-span.     

Expression of interleukin (IL)-4 and IL-5 proteins in asthma induced by toluene diisocyanate (TDI)

BACKGROUND: TDI-induced asthma exhibits clinical, functional and morphological similarities with allergen-induced asthma, suggesting that an immunological mechanism is involved in the sensitization to TDI. In vitro studies using the technique of cloning lymphocytes demonstrated that a great proportion of T-cell clones derived from bronchial mucosa of subjects with TDI-induced asthma produced IL-5 and interferon-gamma, but not IL-4, upon in vitro stimulation. OBJECTIVES: To investigate in vivo the role of IL-4 and IL-5 on the inflammatory response of the bronchial mucosa to TDI in sensitized subjects, we performed a quantitative analysis of bronchial biopsies. METHODS: We obtained bronchial biopsies from six subjects with TDI asthma 48 h after an asthmatic reaction induced by TDI challenge (challenged group), in six subjects with TDI asthma 1-4 weeks after the last exposure to TDI (chronic group), and in six non-asthmatic controls. The number of eosinophils, mast cells, T-lymphocytes, and IL-4 and IL-5 protein positive cells was determined by immunohistochemistry in the area 100 microm beneath the epithelial basement membrane. RESULTS: The characteristic increase of submucosal eosinophils, but not of mast cells and T-lymphocytes, was observed in the subjects with TDI-induced asthma when compared with controls. No differences were detected between the two groups of asthmatics. In the subjects with TDI-induced asthma, cell immunoreactivity for IL-5 was increased when compared with normal controls. There was no difference in the expression of IL-5 protein between challenged and chronic asthmatics. In contrast, the expression of IL-4 protein was increased only in the asthmatic subjects tested after recent exposure to TDI. CONCLUSIONS: We demonstrated that TDI asthma 48 h after specific bronchial challenge was associated with increased numbers of cells expressing IL-4 and IL-5, whereas chronic TDI asthma was associated with increased expression of IL-5, but not of IL-4. The results suggest that subjects who developed TDI asthma exhibit increased production of IL-5 even in the absence of a recent trigger by the exogenous sensitizer and that production of TH2-like cytokines in TDI-induced asthma may not always be co-ordinately regulated in vivo.     

Inhibitory mechanisms of beta-adrenoceptor agonists for immunoglobulin E-mediated experimental allergic reactions in rats

Inhibitory mechanisms of isoproterenol and clenbuterol for immunoglobulin E (IgE)-mediated experimental allergic reactions in rats were studied. IgE-mediated passive cutaneous anaphylaxis, histamine-induced cutaneous reaction and serotonin-induced cutaneous reaction were evoked at the same time in the same rats. Isoproterenol administered intravenously immediately before challenge inhibited all these reactions significantly. Clenbuterol administered intravenously 0-3 h before challenge also significantly inhibited the three cutaneous reactions. The inhibition was maximum when the drug was given 1 h before challenge. Passive cutaneous anaphylaxis was always inhibited more potently than histamine-induced cutaneous reaction and serotonin-induced cutaneous reaction by these beta-adrenoceptor agonists. Passive peritoneal anaphylaxis was caused by injecting an antigen intravenously. Isoproterenol administered intravenously immediately before challenge inhibited the reaction significantly. Clenbuterol administered intravenously 0-3 h before challenge also significantly inhibited passive peritoneal anaphylaxis, maximally so when given 1 h before challenge. In vitro IgE-dependent histamine release from sensitized peritoneal mast cells or mesenteric mast cells was not affected by isoproterenol and clenbuterol. Mouse monoclonal IgE, a foreign protein, administered intravenously decreased rapidly in the circulation. About 50% of the mouse IgE given disappeared in 20 min. The decrease of mouse IgE was partly but significantly inhibited by the beta-adrenoceptor agonists, and the inhibition was abolished by simultaneous treatment with propranolol. These results indicate that direct inhibition of mast cell activation does not contribute to the potent inhibition of in vivo allergic reactions in rats by beta-adrenoceptor agonists, and that inhibition of the allergic cutaneous reaction is partially explained by the inhibition of vascular permeability increases caused by mast cell mediators. Penetration of intravenously administered antigen from blood vessels to peripheral tissues to cause mast cell activation might be inhibited by beta-adrenoceptor agonists, and this could play some role in inhibiting intravenous antigen-induced allergic reactions in rats. Clenbuterol exhibited its maximum action with some latency in vivo, suggesting that some time-requiring process may be involved in the manifestation of its action.     

Reserpine-induced sulphomucin production by goblet cells in the jejunum of rats and its significance in the establishment of intestinal helminths

The present investigation was undertaken to determine whether reserpine-induced increase in the sulphation of the small intestinal goblet cell mucins of rats affects the establishment of intestinal helminths. When Wistar rats were given daily intraperitoneal injections of reserpine for seven days and were then implanted intraduodenally with 500 Strongyloides venezuelensis adult worms, the number of adult worms established in the intestine of reserpine-treated rats was about half of that established in controls. Furthermore, when mast cell-deficient Ws/Ws rats were treated with reserpine and implanted concurrently with S. venezuelensis and Nippostrongylus brasiliensis adult worms, the establishment of the former, but not the latter, was significantly suppressed. These results imply that the physicochemical properties of the mucins produced and secreted by the small intestinal goblet cells may be critical for the establishment of particular species of intestinal helminths.     

Antigen presentation by epithelial cells induces anergic immunoregulatory CD45RO+ T cells and deletion of CD45RA+ T cells

The immunoregulatory effects of alloantigen presentation by tissue parenchymal cells to resting peripheral blood CD4+ T cells was investigated. Coculture of CD45RO+ (memory) and CD45RA+ (naive) T lymphocytes with primary cultures of MHC class II-expressing epithelial cells rendered both populations of T cells hyporesponsive to a subsequent challenge by the same MHC molecule expressed on EBV-transformed lymphoblastoid B cell lines. However, the mechanisms responsible for the allospecific hyporesponsiveness were distinct. For the CD45RO+ T cells, responsiveness was restored by subsequent culture in the presence of IL-2; the addition of IL-2 had no effect on the reactivity of the CD45RA+ T cells. In contrast, the naive T cells were protected from the induction of nonresponsiveness by the presence of a neutralizing anti-CD95 Ab during the culture with thyroid follicular cells. In addition, the hyporesponsive CD45RO+ T cells effected linked suppression, in that they inhibited proliferation against a third-party DR alloantigen when the third-party alloantigen was coexpressed with the DR Ag against which hyporesponsiveness had been induced. These results suggest that recognition of Ag by T cells on tissue parenchymal cells plays an important role in the maintenance of peripheral T cell tolerance, inducing nonresponsiveness in naive and memory T cells by distinct mechanisms.