Preferential expression of anti-bovine serum albumin IgE homocytotropic antibody synthesis and anaphylactic sensitivity in the neonatal rabbit

Induction and maintenance of airway responsiveness to allergen challenge are determined at the age of initial sensitization

Age is an important factor in determining the quantity and quality of immune responses when challenged with allergen. In a model of allergen-induced airway hyperresponsiveness and inflammation, where the sensitization phase and challenge phases can be dissociated in time, we examined the impact of age on these two phases. Sensitization of young mice (1-20 wk), but not older animals (30-40 wk), led to the development of airway hyperresponsiveness, airway eosinophilia, Th2 cytokine responses, and allergen-specific IgE, regardless of the age when the challenge phase was conducted. Thus, age at the time of initial sensitization was shown to be the critical factor dictating the nature of the response to later allergen challenge, as older mice remained responsive to allergen challenge if sensitized at a young age. These effects were shown to be mediated by lung T cells from sensitized young mice. Moreover, the failure of old sensitized mice to mediate these effects was shown not to be the result of active suppression of the responses. These data define the importance of age at initial allergen exposure in dictating subsequent responses in the lung when exposed to allergen and may help to define why asthma, even in adults, is most often initiated in early childhood.

Dust mite-induced asthma in cynomolgus monkeys

Animal models exhibiting high homology with humans at the genetic and pathophysiological levels will facilitate identification and validation of gene targets underlying asthma. In the present study, a nonhuman primate model of allergic asthma was developed by sensitizing cynomolgus monkeys to dust mite antigen. Sensitization elevated allergen-specific serum IgE and IgG levels, and peripheral blood mononuclear cells isolated from sensitized animals released IL-4, IL-5, and IL-10, but not IFN-gamma. Aerosolized allergen decreased dynamic compliance and induced airway inflammation and hyperresponsiveness to aerosolized histamine. Albuterol and dexamethasone inhibited the airway constriction and allergen-induced inflammation, respectively. Airway wall remodeling that included goblet cell hyperplasia, basement membrane thickening, and smooth muscle hypertrophy was particularly evident in neonatally sensitized animals. In contrast to animals sensitized as adults, neonatally sensitized animals exhibited increased sensitivity to adenosine and larger allergen-induced changes in airway resistance and dynamic compliance. These results demonstrate that sensitization of cynomolgus monkeys with dust mite induces asthmalike symptoms, some of which may be dependent on age at the time of sensitization.

Effect of heparin on antigen-induced airway responses and pulmonary leukocyte accumulation in neonatally immunized rabbits

The effect of single administrations of aerosolized heparin, low molecular weight heparin (LMWH) and the linear polyanionic molecule, polyglutamic acid (PGA) were examined on antigen-induced airway hyperresponsiveness and leukocyte accumulation in neonatally immunized rabbits. Adult litter-matched NZW rabbits immunized within 24 h of birth with Alternaria tenuis antigen were treated with heparin, LMWH or PGA prior to or following antigen challenge (Alternaria tenuis). For each drug-treated group, a parallel group of rabbits were treated with the appropriate vehicle. In all groups, airway responsiveness to inhaled histamine and bronchoalveolar lavage (BAL) was performed 24 h prior to and following antigen challenge. Basal lung function in terms of resistance (R(L)) and dynamic compliance (C(dyn)) and acute bronchoconstriction was unaltered by pre-treatment with heparin, LMWH or PGA compared to their respective vehicles 24 h prior to or following antigen challenge. In vehicle-treated animals, airway hyperresponsiveness to inhaled histamine was indicated by an increase in the maximal responses of the cumulative concentration-effect curves to histamine and reductions in R(L)PC(50) and C(dyn)PC(35) values 24 h following antigen challenge. Heparin and LMWH given prior to antigen challenge significantly inhibited the development of airway hyperresponsiveness, whereas PGA did not. When given following antigen challenge, all three drugs failed to inhibit the development of airway hyperresponsiveness. Eosinophil and neutrophil cell numbers in BAL fluid increased significantly 24 h following antigen challenge. Heparin, LMWH and PGA failed to inhibit the increase in cell numbers following antigen challenge whether given prior to or following antigen challenge.

Antigen-induced bronchial hyperresponsiveness in the rabbit is not dependent on M(2)-receptor dysfunction

We have assessed the effect of sensitization to allergen on airway smooth muscle responsiveness and acetylcholine (ACh) release from cholinergic nerves in tracheal preparations from rabbits immunized at birth to Alternaria tenuis and littermate control rabbits injected with saline. ACh release induced by EFS was significantly greater in tracheal preparations obtained from immunized rabbits compared with littermate controls. The ability of the muscarinic-receptor agonist, oxotremorine, to inhibit ACh release to EFS (4 Hz) was not altered by immunization. The contractile response evoked by electrical field stimulation (EFS), ACh and 5-hydroxytryptamine (5-HT) was not significantly altered in tracheal preparations from antigen immunized rabbits compared with littermate controls. Antigen challenge of immunized rabbits did not affect the release of ACh from isolated trachea following EFS, or the ability of oxotremorine to inhibit ACh release. Furthermore, antigen challenge of immunized rabbits failed to alter the contractile response to EFS or ACh, but reduced the contractile potency of 5-HT. These results demonstrate increased ACh release in tracheal preparations following immunization which had no functional consequence on airway smooth muscle responsiveness. Moreover, the increased release in ACh was not associated with an alteration in M(2)-receptor function. Thus, antigen-induced bronchial hyperresponsiveness in the rabbit does not appear to depend upon M(2)-receptor dysfunction.

Latex sensitization in general pediatric surgical patients: a call for increased screening of patients

BACKGROUND/PURPOSE

Latex sensitization is a well-documented occurrence in children with myelodysplastic and urologic anomalies. The incidence of latex allergy in general pediatric surgical patients, however, has not been previously addressed. The purpose of this study was to examine the risk of perioperative latex reactions in a general pediatric surgical practice over a 1-year period.

METHODS

This study examined the occurrence of latex sensitization using two methods. First, the preoperative anesthesia records of patients that have undergone surgery from October 1995 through September 1996 at Mott Children's Hospital were reviewed retrospectively. Second, all patients who had intraoperative anaphylaxis attributable to latex sensitization, including those from three additional hospitals, were evaluated.

RESULTS

During a 12-month period, 1,523 pediatric general surgical operations were performed at the C.S. Mott Children's Hospital. Of these, only 11 operations on five patients were performed under latex precautions. All of these patients had a preoperative diagnosis of latex sensitivity. During the same period, intraoperative anaphylactic reactions caused by latex allergy occurred in two of the general surgical patients (0.13%) at the C.S. Mott Hospital. Four additional cases are also reported from other study hospitals. None of these patients were suspected, based on current screening methods, of having a latex allergy before their surgery.

CONCLUSIONS

Latex allergy is a potentially life-threatening condition in the pediatric general surgical population. Further study is needed to develop criteria to preoperatively identify patients at risk for latex sensitization.

Effect of a 5-lipoxygenase inhibitor and leukotriene antagonist (PF 5901) on antigen-induced airway responses in neonatally immunized rabbits

1. The effect of a single intratracheal dose (10 mg) of PF 5901 (2-[3(1-hydroxyhexyl) phenoxymethyl] quinoline hydrochloride, a specific inhibitor of the 5-lipoxygenase pathway of arachidonic acid metabolism and a leukotriene D4 antagonist) on airway changes induced in response to Alternaria tenuis aerosol challenge was assessed in adult rabbits neonatally immunized. Leukotriene generation was determined in vivo by measuring leukotriene B4 (LTB4) levels in bronchoalveolar lavage (BAL) fluid and ex vivo by measuring calcium ionophore-stimulated production of LTB4 in whole blood. 2. While PF 5901 (10 mg) had no significant effect on the acute bronchoconstriction induced by antigen, this dose was sufficient to inhibit significantly the increase in airway responsiveness to inhaled histamine 24 h following antigen challenge (P < 0.05). 3. Total leucocyte infiltration into the airways induced by antigen, as assessed by bronchoalveolar lavage, was significantly inhibited by pretreatment with PF 5901 (10 mg). However, the pulmonary infiltration of neutrophils and eosinophils induced by antigen was unaltered by prior treatment with PF 5901 (10 mg). 4. PF 5901 (10 mg) had no effect on ex vivo LTB4 synthesis in whole blood. However, the antigen-induced increase in LTB4 levels in BAL 24 h following challenge was significantly inhibited (P < 0.05). 5. We suggest from the results of the present study that the antigen-induced airway hyperresponsiveness to inhaled histamine in immunized rabbits is mediated, at least in part, by products of the 5-lipoxygenase metabolic pathway, and is not dependent on the extent of eosinophil or neutrophil influx into the airway lumen.

A novel animal model for investigating persistent airway hyperresponsiveness

The present study investigates the development and maintenance of airway hyperresponsiveness in neonatally immunized rabbits. Rabbits were immunized within 24 hr of birth with the antigen Alternaria tenuis together with aluminum hydroxide as an adjuvant, followed by repeated antigen and adjuvant administration up to 3 months of age. Anesthetized, spontaneously breathing rabbits immunized according to this protocol exhibited a 3.7- (p < 0.01) and 1.8-fold (p < 0.05) increase in airway responsiveness to inhaled histamine when compared with groups of naive or sham-immunized rabbits, respectively. In the absence of further antigen challenge, these changes in airway responsiveness to histamine in a subpopulation of antigen-immunized rabbits persisted for up to 12 months of age. This hyperresponsiveness was not associated with an alteration in either total or differential inflammatory cell numbers as assessed by bronchoalveolar lavage (BAL), and no significant differences in isolated bronchial smooth muscle responsiveness to methacholine, histamine, theophylline, or electrical field stimulation were observed. These results demonstrate that neonatal immunization of rabbits with Alternaria tenuis can lead to the development of persistent airway hyperresponsiveness, and that the maintenance of this state is unrelated to either a detectable alteration in cellular infiltration within the airway lumen or changes in bronchial smooth muscle responsiveness. It is suggested that neonatal exposure to antigen and adjuvant may be important determinants for the development of persistent airway hyperresponsiveness. This animal model may provide a useful way to investigate the effects of drugs on airway hyperresponsiveness.

The effects of combined histamine and platelet-activating factor antagonism on systemic anaphylaxis induced by immunoglobulin E in the rabbit

Of the mediators released during IgE-induced allergic reactions, it is not known which have the greatest physiologic import in systemic anaphylactic responses. This study describes the effects of histamine and platelet-activating factor (PAF) antagonism (combined) on IgE-induced systemic anaphylaxis in the rabbit. Pretreatment with 30 mumol/kg chlorpheniramine and 30 mumol/kg cimetidine with (Ch/Ci/WEB group) or without (Ch/Ci group) 2.2 mumol/kg of the PAF antagonist WEB 2086 inhibited the anaphylactic alterations in right ventricular pressure, total pulmonary resistance, and decrease in dynamic compliance but not systemic hypotension. Lethality was inhibited only in the Ch/Ci/WEB group. Because previous studies had shown WEB 2086 alone could inhibit the increase in pulmonary resistance, specificity studies were done to determine if WEB 2086 affected histamine activity or release. Responses to intravenously administered histamine (0.54 mumol/kg) were unaffected by WEB 2086 (13.1 mumol/kg). Also, WEB 2086 did not inhibit in vitro antigen-induced basophil degranulation. Thus, the decrease in dynamic compliance and pulmonary hypertension in IgE anaphylaxis appear to be mediated primarily by histamine and the increase in pulmonary resistance by histamine and/or PAF, whereas lethality appears to involve PAF. Some alterations, most notably systemic hypotension, likely involve other allergic mediators.

Antigen enhances neuronally induced contraction of intrapulmonary bronchi from IgE-producing rabbits

The effect of in vitro antigen exposure on contraction induced by electrical field stimulation (EFS) was examined in bronchial rings isolated from rabbits producing specific IgE antibodies. After exposure to antigen, tissues showed an enhanced isometric contractile response to EFS especially at low frequencies, leading to a significant change in the mean slope factor (p less than 0.05) derived from modeling the log frequency response curve using a 4-parameter logistic function. Also, the mean log EF20 +/- SEM decreased from 1.03 +/- 0.05 to 0.88 +/- 0.07 Hz (p less than 0.02). This antigen-induced effect was blocked by pretreatment with 3 microM chlorpheniramine and not observed in unsensitized tissues. Antigen challenge of tissues passively sensitized with IgE (but not IgG) antibodies led to a similar EFS-enhancing effect, significantly reducing the mean slope factor (p less than 0.025). Substituting EFS with exogenous acetylcholine resulted in no antigen-induced enhancement of contraction. The data suggest that antigen-IgE interaction leads to local histamine release sufficient to enhance the function of excitatory airway neurons.

Effect of age on leukotriene B4 production in guinea pig whole blood

We evaluated the effect of age on eicosanoid production in guinea pig blood. Heparinized blood from 7-10-day, 6-week, or 6-month-old guinea pigs was incubated with 150 microM arachidonic acid (AA) for 5 min, followed by stimulation with A23187 (20 micrograms/mL) for an additional 10 min at 37 degrees. The reaction was terminated by centrifugation, and the production of plasma leukotriene (LT) B4 and C4, prostaglandin E2 (PGE2), and thromboxane B2 (TXB2) was determined by enzyme-linked immunoassay (ELISA). LTC4, PGE2, and TXB2 formation were unaffected by age. In marked contrast, production of LTB4 was increased 4- to 5-fold as age increased from 7-10 days (9.51 +/- 2.07 ng/mL) or 6 weeks (8.83 +/- 1.81 ng/mL) to 6 months (40.57 +/- 9.66 ng/mL). To determine the effect of age on the total eicosanoid product profile, blood was stimulated in the presence of [14C]AA, and plasma metabolites were separated by reverse-phase high pressure liquid chromatography (RP-HPLC) and quantitated using on-line radiochemical detection. In addition to increased LTB4 production, a modest increase in 12-hydroxyeicosatetraenoic acid (12-HETE) production was also observed in the 6-month-old animals. Previous studies have demonstrated interference of 12-HETE in the immunoassay of LTB4. Therefore, to validate the authenticity of the plasma leukotriene ELISA measurements, samples were precipitated with methanol and fractionated by RP-HPLC. The fractions co-eluting with [3H]LTB4 or [3H]LTC4 were dried under vacuum and reconstituted in ELISA buffer, and leukotrienes were quantitated. As seen previously, following HPLC purification LTB4 production remained significantly elevated in the 6-month-old guinea pigs, whereas LTC4 production was unaffected by age. To further document the selectivity of this effect on LTB4 production, we evaluated the effect of increasing age on cyclooxygenase or phospholipase A2 (PLA2) activity. Neither cyclooxygenase nor PLA2 activity was elevated as animals matured. In conclusion, the capacity of whole blood to produce LTB4, but not LTC4, TXB2, or PGE2, was elevated markedly in older animals.

Reduced activity of acetylcholinesterase in canine tracheal smooth muscle homogenates after active immune-sensitization

Previous investigations have suggested that immune-sensitization increases airway smooth muscle responsiveness to cholinomimetic stimulation by reducing the rate of degradation of acetylcholine. To examine the hypothesis that increased cholinomimetic responsiveness of tracheal smooth muscle (TSM) caused by immune-sensitization results from inhibition of acetylcholinesterase (AChase) activity, we developed a method for direct measurement of AChase activity in homogenates of TSM obtained from mongrel dogs actively sensitized in vivo to ragweed pollen extract (n = 7) and sham-sensitized littermate controls (n = 7). For both sensitized and control specimens, saturation of AChase was obtained at approximately 3.12 mM substrate (acetylthiocholine); however, maximal enzyme activity in homogenates of ragweed-sensitized tissues was significantly less (0.862 +/- 0.088 absorbance units/min/mg protein [AU/min/mg]) compared to control homogenates (1.590 +/- 0.129 AU/min/mg; P less than 0.001). Kinetic analysis (Eadie-Hofstee plot) indicated similar Michaelis constants (Km) for AChase from ragweed-sensitized (0.360 +/- 0.063) and control (0.336 +/- 0.062) homogenates (P = NS). The concentration of physostigmine eliciting half-maximal inhibition (Ki) of AChase activity also was similar for tissues from sensitized (-7.92 +/- 0.032 log M) and control animals (-7.86 +/- 0.012 log M; P = NS). Pretreatment with selected mediators of anaphylaxis (10(-4) M histamine, 10(-6) M serotonin, 10(-5) M prostaglandin E2, 10(-6) M prostaglandin F2 alpha, and 10(-7) M leukotriene D4) did not affect AChase activity. Our data demonstrate reduced AChase activity in homogenates of canine TSM after active immune-sensitization in vivo. This corresponds to functional augmentation of cholinomimetic contraction in actively sensitized tissues.

Airway cholinergic responsiveness in rabbits in relation to antigen sensitization and challenge

The development of bronchial hyperresponsiveness to cholinergic agents in relation to antigen sensitization and repeated antigen challenge was investigated in a rabbit model. Rabbits immunized to produce preferentially specific IgE antibodies had a modest enhancement of their bronchoconstrictive response (measured as an increase in pulmonary resistance) to aerosolized methacholine compared to sham-immunized and unimmunized controls. A further enhancement was observed subsequent to a series of seven antigen challenges given transtracheally, such that the geometric mean dose of methacholine required to increase pulmonary resistance by 100% (PD100 RL) was 89 cumulative breath units (CBU) compared to 372 CBU for sham-immunized controls and 871 CBU for unimmunized controls (p less than 0.05 for ANOVA). Although methacholine also decreased dynamic compliance, the changes were not different among the three groups. Isolated intrapulmonary bronchi from the three groups did not differ in log concentration of methacholine yielding a half-maximal contraction (log EC50). The range of EC50 values was 15-fold compared to a 90-fold range of PD100 RL. In vivo cholinergic responsiveness of the pupillary muscle did not correlate with bronchial responsiveness. Thus, pulmonary antigen challenge of IgE-producing rabbits produced a marked increase in bronchial responsiveness which did not correlate with in-vitro bronchial responsiveness or with in vivo pupillary responsiveness.

Decreased production of specific antibodies to cow's milk proteins in premature infants during the first six months of life

Concentrations of IgG and IgM antibodies to casein, beta-lactoglobulin, lactalbumin and bovine serum albumin (BSA) in sera of premature infants of less than 36 weeks gestation, at 5 weeks of age, were less than in age-matched term infants. At 6 months of age IgG antibodies to BSA in preterms were still significantly lower than in term infants.

The responsiveness of rabbit bronchial rings to antigen, AGEPC and histamine

Rings of intrapulmonary bronchi isolated from rabbits producing anti-horseradish peroxidase IgE antibodies contracted when exposed to antigen. The contractile response had a lag period of about 1 min, reached a peak at 6 min and then subsided. Bronchi from rabbits with detectable levels of specific IgG (in addition to IgE) antibodies did not differ in response from those with undetectable specific IgG levels. Histamine also contracted rabbit intrapulmonary bronchi with an EC50 of 10 micro (SD 1.29). The response to antigen was completely inhibited with chlorpheniramine (30 microM). In contrast to intrapulmonary bronchi, responsiveness of mainstem bronchi to antigen was observed only occasionally, whereas histamine was equipotent on both mainstem and intrapulmonary bronchi. Thus, the amount of antigen-induced mediator release may be less in the mainstem bronchi. Acetyl glyceryl ether phosphorylcholine, in concentrations up to 10 microM, did not contract either mainstem or intrapulmonary bronchi. This study indicates that histamine is the major mediator of (and acetyl glyceryl ether phosphorylcholine does not significantly participate in) antigen-induced contraction of isolated bronchi from IgE-producing rabbits. The results provide a likely mechanism for the increase in pulmonary resistance observed in IgE anaphylaxis in this species.

The role of histamine in the physiologic alterations of IgE anaphylaxis in the rabbit

The respiratory and circulatory alterations induced by intravenous histamine in the pentobarbital anesthetized rabbit were examined and compared to those alterations associated with IgE anaphylaxis following antigen challenge. Histamine induced several graded alterations including an increase in total pulmonary resistance, a decrease in dynamic compliance, an increase in breathing frequency, a decrease in tidal volume, a rise in right ventricular systolic pressure and systemic hypotension. Qualitatively similar alterations occurred during the anaphylactic response, but a quantitative comparison of the two responses revealed that the respiratory alterations in systemic anaphylaxis corresponded to relatively low equivalent histamine doses, whereas the anaphylactic circulatory alterations exceeded the maximum response obtainable with histamine. Pretreatment with H1 antihistamine competitively blocked all of the ventilatory and lung mechanical changes induced by histamine, but it inhibited only the increase in pulmonary resistance induced by antigen. The right ventricular hypertension induced by histamine was also inhibited by H1 antihistamine but the antigen-induced change in this variable was not significantly attenuated. Inhibition of the histamine-induced systemic hypotension required pretreatment with both H1 and H2 histamine antagonists. Such pretreatment, however, did not attenuate the fall in systemic arterial pressure induced by antigen. H1 antihistamine pretreatment prevented histamine- but not antigen-induced lethality. We conclude that histamine is an important mediator of the increase in pulmonary resistance but is not the major mediator of the other physiological alterations of IgE systemic anaphylaxis in the rabbit.

Heightened cholinergic responsiveness in IgE-producing rabbits

Atopic humans express an array of autonomic nervous system abnormalities. An animal model of IgE-mediated allergy was herein employed to determine if the induction of an IgE antibody response would affect autonomic responsiveness. Rabbits were immunized so as to selectively produce IgE antibodies, and their pupillary miotic and mydriatic responses to cholinergic and alpha adrenergic stimuli, respectively, were determined. IgE-producing rabbits exhibited hyperresponsiveness to cholinergic but not alpha adrenergic stimulation, a pattern resembling that seen in nonasthmatic atopic humans. Repeated sublethal anaphylactic episodes induced in three IgE-producing rabbits did not affect the pattern of autonomic responsiveness when compared to controls challenged with saline, despite clear evidence of increased plasma histamine levels immediately after antigen challenges in the IgE group. This study indicates that elicitation of an IgE antibody response is associated with the concomitant development of cholinergic hyper-responsiveness.

Induction of specific tolerance to ingested soluble protein in neonatal rabbits

The immune response of adult rabbits to low concentrations of BSA in their drinking water has been a useful model to study systemic immunity initiated in gut-associated lymphoid tissue. In the present study, this model was applied to neonatal rabbits. 21 New Zealand white neonatal rabbits were fed a cow-milk formula containing 0.17% BSA from the 5th to the 32nd day of life. At this time, anti-BSA was detected in only 5 animals. A subsequent intravenous injection of 50 mg BSA demonstrated a weak anti-BSA response in 6 and complete tolerance in 15 animals. Specificity of this tolerance was demonstrated by a vigorous response to 100 mg HSA, given at 60 days of age, in all of 9 animals tested. At 8 months of age, 2 of 3 animals still failed to respond to intravenous BSA, one rabbit had a low primary-type response. Determination of absorbed antigenic BSA on day 32 showed a mean of 1.09 +/- 0.47 (S.E.) microgram BSA per ml of serum, i.e. a considerably higher concentration than seen in adult animals fed similar antigen concentrations. These observations suggest that orally induced tolerance in neonatal rabbits may be due to an effect on systemic lymphoid tissue following increased antigen absorption rather than a direct antigen effect on gut-associated lymphoid tissue.

A comparative study of the morphology of the systemic anaphylactic reaction (SAR) and the shock reaction induced by antigen-antibody complexes in rabbits

Differences in the morphological picture of the systemic anaphylactic reaction (SAR), and of the shock reaction induced by antigen-antibody (ag-ab) complexes in rabbits, are described. In rabbits SAR is characterized by acute distension of the lungs, with oedematous swelling in the vicinity of bronchi and veins, intravascular stasis of basophils without degranulation or visible fixation of the inducing antigen, small clusters of blood platelets, leukostasis, minimal decomposition of neutrophil granulocytes and absence of circulating or fixed ag-ab complexes. The shock reaction induced by ag-ab complexes is characterized by acute distension of the lungs without bronchospasm, swelling of the vicinity of bronchi and veins, hyaline thrombi particularly in the pulmonary microcirculation, leukostasis, formation of antigen-antibody complexes and thrombocyte clusters in the microcirculation, and by phagocytosis of these complexes and thrombocytes by various cells.

Absence of immunological hypertensitivity to dietary cow's-milk proteins in infant rabbits

1. Rabbits hand-reared on a diet based on cow's milk frequently experience convulsive and sometimes fatal reactions to their feed. These have been thought to be caused by immunological hypersensitivity to cow's milk. 2. This explanation has been re-examined and found to be untenable.