Uptake of polypeptide fragments of proteins by rat intestine in vitro and in vivo

Minute amounts of intact proteins were previously shown to be taken up from the intestine into the systemic circulation of mature animals; fragments were not detected. In this study, we sought evidence for uptake of fragments in both in vitro and in vivo experiments. Polypeptide fragments produced by pepsin digestion of bovine serum albumin (ranging in molecular weight from approximately 6000 to 25,000) were labeled with 125I. Everted jejunal gut sacs prepared from rat intestine were incubated with labeled fragments. After incubation, fluid exposed to the serosal surface was applied to a Sephadex G-50 gel permeation column. Radioactivity was detected in fractions corresponding to the elution position of the fragments. Transfer of fragments from the mucosal to the serosal surface was temperature-dependent. In in vivo studies, labeled fragments were infused into the jejunum of rats. Blood samples obtained from a mesenteric vein or the portal vein contained labeled fragments. After infusion of unlabeled fragments, nanogram amounts of immunoreactive fragments were detected by radioimmunoassay of mesenteric and portal venous blood. Thus, polypeptide fragments of a potential food protein were capable of being transferred across the mucosa in vitro and in vivo. Failure to detect fragments in the systemic circulation most likely results from their rapid clearance.

T cell populations in the lacrimal gland during aging

The present study examined the influence of age and gender on T cell populations in the lacrimal gland. Lacrimal (exorbital) glands were obtained from male and female rats at 19 days (pre-puberty), 9 weeks (adult) and 14 months (mid-life) of age and tissues were processed for T cell subset identification. In females, the density of total (W3/13+ and OX 19+), helper/inducer (W3/25+) and suppressor/cytotoxic (OX 8+) T cells underwent a significant increase in tissues from before, to after puberty. Following this rise, the density of all T cell populations decreased in glands from young adult to midlife females. This pattern of accumulation contrasted with the T cell profile presented by glands from males: T cell densities appeared unaffected from 19 days to 9 weeks of age, and then either declined (OX 19+, W3/25) or remained unchanged (W3/13+, OX 8+) in tissues of 14 month rats. An influence of gender on the distribution of T cells was also apparent if results were corrected for age-associated variations in lacrimal gland weight. Thus, the absolute number of all T cell populations rose dramatically in glands of both sexes from pre- to post-puberty. However, from 9 weeks to 14 months of age, the total content of W3/13+, OX 19+, W3/25+ and OX 8+ lymphocytes decreased 2-fold in glands of females, but did not vary in tissues of males. Of interest, the number of W3/25+ and OX 8+ cells was analagous in all age groups examined. Moreover, the combined total of W3/25+ and OX 8+ cells was greater than that of W3/13+ or OX 19+ cells at every age.(ABSTRACT TRUNCATED AT 250 WORDS)

Attenuation of rat conjunctival response by repeated hapten applications

Attenuation of the rat conjunctival response by repeated topical challenge with dinitrophenyl (DNP) hapten was demonstrated in our study. Adult rats were immunized by intraperitoneal injections of dinitrophenylated Ascaris suum extract (DNP-Asc) and alum. Serum levels of anti-DNP homocytotropic antibody were determined by passive cutaneous anaphylaxis in rats prepared with antibody 48 hours earlier. In other animals, topical challenge was performed by applying N,N'-di-2,4-DNP-L-lysine (di-DNP-lysine) in phosphate-buffered saline (PBS) to one eye; PBS alone was applied to the fellow eye. The degree of conjunctival reaction was assessed clinically, and ocular tissues were processed for histological evaluation. The intensity of the conjunctival reaction and extent of mast cell degranulation were significantly greater after one challenge with di-DNP-lysine than after multiple challenges. In the multiple-challenge group, the contralateral eye remained responsive to a single challenge with di-DNP-lysine. These results may have implications for therapeutic interventions in ocular anaphylaxis.

Plasma immunoreactive-trypsin(ogen) levels during development

We previously showed that the uptake of intact trypsin from the intestine of suckling animals was greater than that of weaned animals. To extend these studies, we measured plasma cationic immunoreactive-trypsin(ogen) in human subjects aged 3 days to 43 years. In agreement with the observation of other investigators, we found that the concentration of cationic immunoreactive-trypsin(ogen) was significantly increased in 3-day-old infants compared with other age groups. None of the cationic immunoreactive-trypsin in adult samples was bound to alpha 1-antitrypsin, whereas 28% of cationic immunoreactive-trypsin in infant samples was bound to alpha 1-anti-trypsin.

Late-phase reaction in topically induced ocular anaphylaxis in the rat

A cellular late-phase reaction is described in a rat model of topically induced ocular anaphylaxis. Rats were immunized with dinitrophenylated Ascaris suum extract and alum and were tested for active cutaneous anaphylaxis on day 13. Rats with a strong skin test response were selected for ocular challenge with di-DNP-lysine. Macroscopic observation and histologic evaluation were performed at 1, 6, and 24 h. In rats showing a moderate macroscopic ocular response at 1 h, mast cell degranulation was significantly increased at 1 h; no significant increase in eosinophils, neutrophils or lymphocytes was found in the conjunctive of these animals. In rats showing a marked macroscopic ocular response at 1 h, mast cell degranulation was significantly increased at 1 and 6 h; the number of eosinophils was significantly increased at 1 and 6 h, and of neutrophils at 6 h only. At 24 h, neutrophil and eosinophil numbers returned to baseline levels. There was no macroscopic evidence of a late-phase response in either group of animals. Our results suggest that, in keeping with earlier observations in human skin, a strong early response to antigen is required for the development of a late-phase ocular response in the rat.

Effects of topical pre-treatment with dexamethasone on the immediate and late phases of topically induced ocular anaphylaxis in the rat

We tested the effects of pre-treatment with dexamethasone on topically induced ocular anaphylaxis in the rat. Rats were immunized with dinitrophenylated Ascaris suum extract and challenged with di-DNP-lysine. Dexamethasone was administered topically once (24, 6, or 1 h before challenge) or three times (6, 4, and 2 h before challenge). A single pre-treatment given at 24 or 6 h had no significant effect. A single pre-treatment 1 h before challenge reduced the extent of edema assessed histologically but not clinically, and had no significant effect on the eosinophil count in conjunctival tissue examined 6 h after challenge. Eyes pre-treated with dexamethasone 6, 4, and 2 h before challenge showed a significant reduction in conjunctival edema assessed histologically and clinically 1 h after challenge. In addition, 6 h after challenge the number of eosinophils was significantly reduced. We conclude that repeated pre-treatment with dexamethasone can suppress both the immediate phase and the cellular late phase of topically induced ocular anaphylaxis.

Trichloroacetic acid (TCA) precipitability of 125I in the blood of mice fed 125I

A recent study showed that after feeding 125I-labelled proteins or free 125I to mice, as much as 40% of total radioactivity in the circulation precipitated upon mixing whole blood with 10% trichloroacetic acid. We examined this potential limitation to the use of radiolabelled tracers for studies on intestinal digestion of proteins and protein uptake, and identified its mechanism. BALB/c mice were gavage-fed or injected intravenously (i.v.) with Na125I. Blood obtained at 15 min was added directly to 10% trichloroacetic acid (TCA) or was processed to obtain serum or plasma. On mixing with 10% TCA, 25-33% of the radioactivity in whole blood was precipitated; less than 2% of the radioactivity in plasma or serum was precipitated. In vitro studies identified hemoglobin as the primary carrier protein participating in this reaction. If hemoglobin was replaced by methemoglobin or cyanomethemoglobin, then the reaction with 125I did not occur, suggesting that iron in the heme group may be the site for 125I binding and that iron must be in its reduced or ferrous form (Fe2+). The administration of non-radioactive NaI in vivo or its addition to reaction mixtures in vitro completely inhibited the precipitation of 125I by hemoglobin in the presence of TCA. Thus the addition of non-radioactive iodide to TCA stock solutions may effectively prevent non-specific binding of 125I to free hemoglobin released unintentionally during venipuncture or at other stages of blood processing.

Effect of multiple applications of compound 48/80 on mast cells of rat conjunctiva

We sought to determine the effect on rat conjunctival mast cells of chronic exposure to a degranulating agent. Compound 48/80 (250 micrograms in 10 microliter) was applied daily to the ocular surface of rats for a total of 13 treatments administered in 17 days. A single application of compound 48/80 was given to rats for comparison. Four groups of animals (6 in each group) were evaluated 1 or 48 h after the last application of compound 48/80 in both chronic exposure and single exposure studies. Although a single exposure to compound 48/80 induced significant degranulation of mast cells in animals observed 1 h after treatment, no significant degranulation of mast cells was observed 1 h after the last dose of compound 48/80 was given to rats whose conjunctiva had been chronically exposed to this degranulating agent. Thus, multiple applications of compound 48/80 attenuated the mast cell response to compound 48/80. This acquired tolerance to compound 48/80 was reflected in the lessened clinical signs in rats receiving repeated applications compared with those given a single application.

The immune response of the lacrimal gland to antigenic exposure

This study probed the influence of antigenic exposure on the immunological response of the lacrimal gland. We utilized the germfree rat as a model system to monitor tissue and tear immunoglobulin changes following transfer of these animals into an antigen-laden, conventional environment. The number of IgA- and IgM-containing cells in the lacrimal glands of germfree rats was 5 to 8 fold less than that of conventional controls. This reduced immunological expression in germfree animals also extended to tear IgA levels, which were significantly decreased. No effect of germfree conditions was found on the tear content of secretory component (SC). Transfer of rats from a germfree to a conventional environment resulted in a significant increase in the number of IgA- and IgM-containing cells in the lacrimal gland. By four weeks after 'conventionalization', the number of Ig-containing cells in lacrimal tissue was similar in both ex-germfree and conventional rats. In addition, 'conventionalization' led to a significant increase in the tear content of IgA: within four weeks following exposure to a conventional environment, tear IgA levels in ex-germfree rats were equivalent to those of age-matched, conventional controls. Overall, our results demonstrate that the secretory immune system of the lacrimal gland reacts to antigenic challenge with an increased immunological response.

Late-phase reaction and tear fluid cytology in the rat ocular anaphylaxis

Tear fluid cytology is described for the early and late phases of ocular anaphylaxis in actively immunized Sprague-Dawley rats. Tears were collected from both eyes of the rats before challenge and at 1, 2, 4, 6, 8, 10, 12, 24, and 48 h after topical challenge with di-DNP-lysine in one eye and PBS in the fellow eye. Results showed a statistically significant increase in the Aggregate Cell Rating, which represents the aggregate scores in neutrophil, eosinophil, lymphocyte, and atypical epithelial cell levels, in antigen-treated vs control eyes. This report is the first to use a cytologic study of tear film to detect the late phase of ocular anaphylaxis in the rat. Cytology of the tear film could be applied to the study of allergic conjunctivitis in both animals and humans.

A hapten model of topically-induced ocular anaphylaxis in the rat

A hapten (DNP) model of topically induced ocular anaphylaxis has been developed. Rats immunized with DNP-Ascaris were skin-tested with DNP-bovine serum albumin (DNP-BSA) and Evans blue and challenged topically with varying amounts of di-DNP-lysine. The degree of clinical conjunctival edema was assessed, and eye tissues were evaluated histologically. Clinical conjunctival edema and histologic mast cell degranulation increased with higher concentration of di-DNP-lysine. In general, rats with positive skin tests showed more clinical conjunctival edema and more mast cell degranulation than those with negative skin tests. Three other groups of rats with positive skin tests to the DNP-BSA were injected intravenously with 125I-BSA and challenged topically with di-DNP-lysine. Retention of 125I-BSA in ocular adnexa and in globes was higher in di-DNP-lysine- than in PBS-challenged eyes. The hapten model simulates the ocular component of human hay fever in that ocular anaphylaxis is induced in immunized rats by topical challenge with antigen alone.

Elevated levels of alpha 2-macroglobulin-protease complexes in infants

Proteases form stable complexes with alpha 2-macroglobulin (alpha 2-MG) in human plasma. We previously showed that the intestine of newborn rabbits takes up greater amounts of proteases than the intestine of weaned animals, and we suggested that the same phenomenon might occur in the human newborn. To test this possibility, alpha 2-MG complexes were sought in plasma from 3-day-old human infants and adults. In addition, the level of alpha 2-MG was measured. The concentration of alpha 2-MG complexes and of alpha 2-MG was significantly increased in the plasma of infants compared to adults. We suggest that the elevated levels of alpha 2-MG complexes in infants may reflect the enhanced uptake of proteases from the intestine. In addition, there may also be decreased clearance of complexes by the mononuclear phagocytic system in infants. The elevated levels of alpha 2-MG in the infant may reflect a response to the need for neutralizing proteases absorbed from the intestine.

In vivo intestinal uptake of immunoreactive bovine albumin in piglet enteritis

We examined the uptake of bovine serum albumin (BSA) from the intestine into the circulation of 3-week-old piglets infected with transmissible gastroenteritis virus. Transfer of immunoreactive bovine serum albumin (iBSA) from the intestinal lumen into the circulation was enhanced during both the early invasive phase of this viral enteritis (12-h postinoculation) and the diarrheal phase (84-h postinoculation). In some animals, enhanced uptake persisted into the recovery phase, 324 h after inoculation. Gel filtration studies suggested that iBSA had the molecular size characteristic of native BSA; no immunoreactive fragments of BSA were detected. Based on studies of two animals, the half-life of iBSA approximated that of porcine albumin. Further study is required to determine the immunological consequences of the enhanced uptake of protein occurring during viral infection of the intestine.

Conjunctival basophil hypersensitivity in the guinea pig

We have induced a basophil hypersensitivity reaction in the upper tarsal conjunctiva of the guinea pig by methods that induce a comparable basophil hypersensitivity reaction in the flank. The inflammatory cell infiltrate in this reaction contained large numbers of basophils and eosinophils with accompanying neutrophils and monocytes. Ocular tissue can serve as a priming site for systemic immunization and also for elicitation of a secondary flare after challenge with antigen. Very few inflammatory cells were observed in the cutaneous epithelium of either primary or secondary flares. In contrast, the mucosal stroma and epithelium contained large numbers of inflammatory cells (basophils, eosinophils, and neutrophils), suggesting directed cellular movement onto the ocular surface. The lesion of ocular basophil hypersensitivity in the guinea pig has features in common with two human eye diseases, vernal conjunctivitis and contact lens-associated giant papillary conjunctivitis. We hypothesize that the acute basophil hypersensitivity reactions of the conjunctiva are transformed into chronic inflammatory and proliferative states in vernal conjunctivitis and giant papillary conjunctivitis.

Transfer of protein antigens into milk after intravenous injection into lactating mice

We investigated the transfer of bovine serum 125I-albumin (125I-BSA), bovine 125I-gamma-globulin (125I-BGG), 125I-ovalbumin (125I-OVA), and 125I-beta-lactoglobulin (125I-BLG) from the blood into the milk of lactating mice. Equal amounts (by weight) of the radiolabeled proteins were injected intravenously into mice 1 wk postpartum. Total radioactivity, trichloroacetic acid-precipitable radioactivity, and specifically immunoprecipitable radioactivity were measured in serum, mammary gland homogenate, and milk. Clearance of immunoreactive OVA (iOVA) and iBLG from the circulation was more rapid than iBSA and iBGG. The radioactivity in mammary tissue associated with BSA and BGG was greater than 70% immunoprecipitable throughout the 4-h test interval; 125I-OVA and 125I-BLG were less than 12% precipitable 1 and 4 h after injection. In milk obtained at 4 h, there was an approximately 10-fold greater accumulation of iBSA or iBGG than of iOVA or iBLG. These experiments demonstrate that protein antigens differ in their ability to transfer from maternal circulation into milk. The transfer into milk appeared to be in proportion to persistence of the antigens in the maternal circulation.

Immune complex-induced enteropathy in the rat. I. Clinical and histological features

Adult male Sprague-Dawley rats injected with preformed rat anti-bovine serum albumin antibody-bovine serum albumin complexes prepared in fivefold antigen excess, developed intestinal lesions consisting of annular bands of serosal hyperemia alternating with nonhyperemic bands, causing a striped appearance. Histologically, vascular congestion and mucosal edema were observed; more severe lesions were accompanied by hemorrhage, epithelial necrosis and sloughing, and modest polymorphonuclear leukocyte infiltration. The lesions developed rapidly and were accompanied by hemoconcentration. A correlation between the dose of immune complexes injected and the intensity and extent of intestinal lesions was noted. The pathogenetic mechanism of the lesions was not determined. The similarity of the lesions to those observed in systemic anaphylaxis in the rat and experimental and clinical shock was cited. The implications of immune complex-induced enteropathy for studies of immune complex clearance by the mononuclear phagocyte system were considered.

Cyclooxygenase blockade elevates leukotriene E4 production during acute anaphylaxis in sheep

We examined changes in the levels of eicosanoids in blood and pulmonary lymph of anesthetized sheep undergoing acute anaphylaxis. Within 1-3 min of intravenous antigenic challenge of previously sensitized sheep, there were approximately 7-30-fold elevations in mean arterial plasma levels of thromboxane B2 and 6-ketoprostaglandin F1 alpha, respectively, as measured by RIA. Negligible changes in levels of these cyclooxygenase products were found in both nonsensitized sheep and in sensitized sheep treated with indomethacin before antigenic challenge. In contrast, no changes in levels of sulfidopeptide leukotrienes (SPLT) in pulmonary lymph were detectable by RIA during anaphylaxis in sensitized or nonsensitized sheep, but levels of SPLT in indomethacin-treated sensitized sheep increased more than fivefold above levels in lymph from both other groups of animals. The immunoreactive SPLT in lymph from indomethacin-treated sheep was accounted for as LTE4, as demonstrated by mobility on HPLC and absorbance at 280 nm. These results support the possibility that certain undesirable effects of nonsteroidal antiinflammatory drugs, such as cardiopulmonary reactions in aspirin-sensitive individuals, and impaired renal and cardiac function during therapy with these drugs, may be related in part to augmented synthesis of the 5-lipoxygenase pathway products, especially those of the sulfidopeptide class. Increased LT production could also limit the antiinflammatory effectiveness of these drugs in many disease states.

Worm antigen-induced ocular anaphylaxis in rats infected with Nippostrongylus brasiliensis

A model of topically induced conjunctival anaphylaxis has been developed. Male Sprague-Dawley rats were immunized by infection with 3000 Nippostrongylus brasiliensis larvae and challenged topically on the eye 4 weeks later. Application of worm antigen alone did not induce clinical (conjunctival edema) or histologic (mast-cell degranulation) signs of anaphylaxis. Topical challenge with antigen 15 min after topical application of dithiothreitol (DTT), a mucolytic agent, elicited conjunctival edema and mast-cell degranulation within the first hour after challenge. At 6 and 24 hr, no clinical change was evident and conjunctival mast cells had again become granulated. At none of the three intervals (1, 6 and 24 hr) was there a significant increase in neutrophils, lymphocytes, eosinophils or macrophages in tissues from DTT-pretreated, antigen-eyes. The present model of ocular anaphylaxis resembles the ocular component of human hay fever in that sensitization prior to challenge is essential, the antigen is presented topically to the ocular tissues, conjunctival edema is the clinical manifestation and mast cell degranulation characterizes the histologic changes.

Characterization of a localized basophil hypersensitivity lesion in guinea pig conjunctiva

Basophils accumulate in response to antigen challenge in cutaneous basophil hypersensitivity (CBH) reactions. Two ocular diseases, vernal conjunctivitis and contact-lens-associated conjunctivitis, are also characterized by this histopathology. We have refined a model previously developed in guinea pig conjunctiva by precisely defining the site of antigen injection and correlating the site with the clinical and histologic changes. Guinea pigs were primed by an intradermal injection of keyhole limpet hemocyanin (KLH) in the flank and challenged (Day 6) by injection of a small bolus of KLH just under the conjunctival epithelium. Twenty-four hours later histologic examination showed a perivascular infiltrate of inflammatory cells containing large numbers of basophils. Eosinophils, neutrophils, macrophages, and mast cells were also seen. Serial sections of the reaction site showed discrete boundaries. At all sites examined in antigen-challenged tissues, there were significantly more basophils than in control-injected conjunctiva. Insertion of a sterile needle or injection of PBS or KLH into normal conjunctiva induced a significant increase in neutrophils and some macrophages. Injection of graded doses of antigen into the conjunctiva of primed animals, resulted in a dose-dependent increase in basophils up to 50 micrograms KLH (optimal dose).

Influence of circulating maternal antibody on the transfer of dietary antigen to neonatal mice via milk

125I-BSA injected intravenously into lactating mice persisted in the circulation for 4 h, entered the mammary gland, and was transferred to the neonate via the milk. When injected with anti-BSA antibodies, it was rapidly cleared from the circulation. Although animals receiving anti-BSA antibodies transferred more radioactivity to the neonate via the milk, the radioactivity was not TCA-precipitable or bound to staphylococcal protein A, nor was it immunoreactive. These findings suggest that circulating maternal antibody can limit the transfer of specific protein antigen from mother to newborn.

Topically induced ocular anaphylaxis in rats immunized with egg albumin

A model of topically induced ocular anaphylaxis was developed. Male Sprague-Dawley rats were immunized by intraperitoneal injections of egg albumin (EA) and alum and topically challenged with EA. Application of EA induced clinical (conjunctival edema) and histologic (mast cell degranulation) signs of anaphylaxis, when the antigen was preceded by topical application of dithiothreitol (DTT), a mucolytic agent. Rats challenged by four EA applications did not differ significantly in clinical edema or mast cell degranulation from those challenged by one EA application at the same (0.1 M DTT) pretreatment level, but there was significantly greater histologically assessed edema in the eyes challenged four times.

Effect of anaphylaxis on conjunctival goblet cells

Rats undergoing ocular anaphylaxis induced by systemic or local injection of antigen, topical application of antigen, or topical application of compound 48/80 were evaluated conjunctival goblet cell changes that might be related to anaphylaxis. The number of goblet cells in 1 micron, alkaline Giemsa-stained sections averaged 500/mm2 of epithelium in normal rats; this number was not significantly changed in any of the experimental groups. Goblet cells in control rats occasionally demonstrated evacuation of their contents (less than 1%) or upward displacement of the intracellular bolus of mucus (about 1%); these percentages were not increased in anaphylaxis. Topical application of 2.0 micrograms of histamine induced an intracellular displacement of mucus in both control animals and animals undergoing anaphylaxis. These findings suggest that in ocular anaphylaxis the amount of histamine released may be insufficient to produce such intracellular changes. Our results indicate that in ocular anaphylaxis in the rat, there is no light microscopic evidence of increased mucus discharge from conjunctival goblet cells. Increased mucus in secretions of patients with ocular allergic syndromes may not be attributable to anaphylactic mechanisms alone.