The impact of CD14 polymorphisms on the development of soluble CD14 levels during infancy.

CD14 is a receptor involved in the recognition of lipopolysaccharide and other bacterial wall components that may be involved in the balance between infectious and allergic disease and the early polarization towards TH1. Our group has shown an association between polymorphisms in the 5' flanking region of the CD14 gene and plasma soluble CD14 (sCD14) levels at 11 years of age. However, whether this association is present at birth and in infancy remains to be determined. In this study, we measured sCD14 levels in plasma from the umbilical cord (n = 387) and at 3 months (n = 357) and 1 year (n = 312) of age in non-selected healthy infants to assess their relationship with CD14 genotypes at -4190, -2838, -1720 and -260 (relative to translation start site). There was no relation of CD14 genotypes with sCD14 at birth. However, there was a significant association between CD14 genotypes and sCD14 as early as 3 months. Longitudinal analysis suggests that CD14 polymorphisms modulate sCD14 levels up to 1 year of age. This association early in life may have an impact on TH1 polarization and subsequent protection against allergic disease.

Dynamic changes in sensitization to specific aeroallergens in children raised in a desert environment.

BACKGROUND: Allergen skin test reactivity and total serum IgE are objective measures used to characterize and help diagnose allergic diseases. Cross-sectional studies have shown that overall aeroallergen skin test reactivity increases throughout childhood. However, little attention has been paid to whether individual aeroallergen remittance occurs, which could distort or mask relationships to disease. OBJECTIVE: To access the incidence and remittance of skin test reactions to individual allergens in children aged 6-11 years. METHODS: Longitudinal sensitization to six aeroallergens and total IgE were assessed in 828 children raised in the semi-arid US southwest at ages 6 and 11 years. RESULTS: New sensitization (to any allergen) between 6 and 11 years occurred in 30.2% of children compared with 39.7% before age 6 years. The rate of complete remittance from positive to negative between ages 6 and 11 years was 8.2%, and total IgE at age 6 years was not predictive. Remittance rates for individual allergens were high and variable (19-49%). The perennial allergens Bermuda and Alternaria were early sensitizers and had low remittance rates. Early sensitization to the four seasonal allergens was less common and more subject to remittance with the bulk of sensitization occurring between 6 and 11 years. CONCLUSION: This study shows that sensitization to individual aeroallergens in childhood is dynamic and indicates the limitation of single point assessment of skin test reactivity.

Differential control of eosinophil survival by glucocorticoids.

Glucocorticoids are effective drugs for eosinophil-related disorders, such as asthma and allergy. Previous studies have demonstrated that glucocorticoids increase eosinophil apoptosis and block the survival effect of submaximal concentrations of interleukin-5 (IL-5). We investigated the effect of glucocorticoids on eosinophil survival in the presence of a higher concentration of IL-5 (1 ng/ml), comparable to IL-5 levels in bronchoalveolar lavage and sputum specimens from patients with asthma. In contrast to incubation in the presence of submaximal concentrations of IL-5, the addition of dexamethasone (DEX) to media containing 1 ng/ml IL-5 led to a significant increase in eosinophil cell viability from 58 +/- 6.9% to 87 +/- 2.4% ( p < 0.005) after 72 hours in culture. We found that RU486 blocked the DEX effect on cell viability confirming that glucocorticoid receptor functions are required. We investigated the possibility that the glucocorticoid enhancement of eosinophil survival may be due to an effect on IL-5 receptor expression. Our results show that the IL-5 associated decrease in IL-5 receptor alpha-subunit expression was blocked significantly after 24 hrs in culture with media containing IL-5 plus DEX compared to IL-5 alone. It is tempting to speculate that the observed glucocorticoid enhancement of eosinophil survival in the presence of elevated concentrations of IL-5 could be a mechanism that contributes to glucocorticoid resistance in asthma.

CD14: a bridge between innate immunity and adaptive IgE responses.

Total IgE levels are known to be under genetic control. Linkage studies have indicated that one or more loci on chromosome 5q may control total IgE, as well as asthma and bronchial hyperresponsiveness to non-specific stimuli. Our group has undertaken a systematic analysis of chromosome 5q, and has recently characterized five single nucleotide polymorphisms at position -1619, -1359, -1145, -809, and -159 in the promoter of the gene encoding CD14, the myeloid pattern recognition receptor that is critical for efficient innate immune responses to lipopolysaccharide and bacterial ligands. Individuals homozygous for the three major CD14 haplotypes found in the Children Respiratory Study population (n = 390) were analyzed for serum levels of total IgE and soluble CD14. A strong inverse correlation was found between these two parameters, i.e. carriers of the -1359T/-1145A/-159C haplotype had the highest levels of IgE, and the lowest levels of sCD14. Conversely, carriers of the -1359G/-1145G/-159T haplotype had the highest levels of sCD14 and the lowest IgE values. Our results suggest that genetic variation in CD14, a key gene of innate immunity, may modulate the effects that exposure to bacterial ligands has on the development of Th2 responses.

Differences in proliferation of the hematopoietic cell line TF-1 and cytokine production by peripheral blood leukocytes induced by 2 naturally occurring forms of human IL-3.

BACKGROUND: A naturally occurring polymorphism in the coding region of the human IL3 gene leads to a change in amino acid residue 8 from proline to serine. OBJECTIVE: We sought to determine whether the 2 different forms of IL-3 varied in function. These different forms are available as recombinant proteins (recombinant human IL-3/proline 8 [rhIL-3/P8] and recombinant human IL-3/serine 8 [rhIL-3/S8]). METHODS: The erythroleukemic cell line TF-1 was incubated with varying concentrations of rhIL-3/P8 or rhIL-3/S8 to determine the capacity of each type of IL-3 to induce proliferation. Human leukocytes were primed with rhIL-3/P8 or rhIL-3/S8 for up to 24 hours and then stimulated with anti-IgE and assessed for leukotrienes (LTs), IL-4, and TNF-alpha. RESULTS: Proliferation of TF-1 cells was induced by both forms of IL-3 at 48 and 72 hours but to a greater degree by rhIL-3/P8. In contrast, the mean fold increase over control values of LT and IL-4 production was higher after priming the cells with rhIL-3/S8 versus rhIL-3/P8. Additionally, TNF-alpha production was greater (and reached significance only) for rhIL-3/S8. This activity was independent of IgE and thus directly stimulated by IL-3. Studies with basophil-enriched and basophil-depleted cell preparations revealed that LT production was evident only from the former and TNF-alpha only from the latter. CONCLUSION: We conclude that the 2 naturally occurring forms of human IL-3 have similar spectra of activities on cells with IL-3 receptors, but the 2 forms have reversed relative efficacies for promoting proliferation (rhIL-3/P8 > rhIL-3/S8) compared with priming or inducing mediator secretion (rhIL-3/S8 > rhIL-3/P8).

A Polymorphism* in the 5' flanking region of the CD14 gene is associated with circulating soluble CD14 levels and with total serum immunoglobulin E.

Total serum immunoglobulin (Ig)E levels are genetically regulated, but the mechanism of inheritance is not well understood. Cytokines produced by T-helper (Th)1 and Th2 lymphocytes control IgE synthesis. Bacterial antigens may favor the development of Th1 cells from naive CD4-positive T cells through a CD14-dependent pathway. CD14 is constitutively expressed on the surface of monocytes and macrophages, and is also present in serum in a soluble form (sCD14). The CD14 gene maps to chromosome 5q31.1, a candidate region for loci regulating total serum IgE. We hypothesized that genetic variants in the CD14 gene could influence Th-cell differentiation and thus total serum IgE. We identified a C-to-T transition at base pair -159 from the major transcription start site (CD14/-159). Among 481 children recruited from a general population sample, frequency of allele C was 51.4%. TT homozygotes had significantly higher sCD14 levels than did carriers of both the CC and CT genotypes (P = 0.01). TT homozygotes also had significantly lower levels of IgE than did carriers of the other two genotypes, but differences were significant only among children who were skin test-positive to local aeroallergens (P = 0.004). There was no association between CD14/-159 and either interleukin (IL)-4 or interferon (IFN)-gamma responses by peripheral blood mononuclear cells. However, IFN-gamma and IL-4 responses were positively and negatively correlated, respectively, with serum sCD14 levels. We conclude that CD14/-159 plays a significant role in regulating serum sCD14 levels and total serum IgE levels.

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.

Effect of specific IgG on IgE-induced systemic anaphylaxis in the rabbit.

Immunization of rabbits as neonates and periodically thereafter has been shown to induce the long-term preferential production of specific IgE antibodies. Specific IgG antibodies are not detected in the majority (greater than 70%) of rabbits when classical immunological detection techniques are used, including heterologous PCA in guinea-pig skin. Nevertheless, in this study we demonstrate that all rabbits neonatally immunized to the antigen horseradish peroxidase (HRP) do produce low levels of specific IgG antibody detectable by an ELISA technique. Serum levels of anti-HRP IgG were found to be log normally distributed, with a geometric mean for the heterologous PCA-negative sera of 31.6 X/divided by 2.69 micrograms/ml. Serum anti-HRP IgE levels (log2 homologous PCA titres) are bimodally distributed. Specific IgG and IgE levels in individual rabbits have a significant direct relationship. Six heterologous PCA-negative and seven heterologous PCA-positive rabbits were challenged intravenously with HRP. All of the respiratory and circulatory alterations typical of IgE anaphylaxis occurred in every challenged rabbit. Regression analysis of percentage changes in the physiological variables vs log specific IgE level indicated that none of the changes was either directly or inversely related to the specific IgG levels. Also the mean changes of the heterologous PCA-positive vs negative rabbits did not differ significantly. Thus, we could find no evidence for either a blocking or enhancing effect of the specific IgG antibodies (range 10-529 micrograms/ml serum) on the IgE-induced anaphylactic reaction.

Participation of platelets in the physiologic alterations of the AGEPC response and of IgE anaphylaxis in the rabbit. Effects of PGI2 inhibition of platelet function.

To further clarify the platelet dependence of acetyl glyceryl ether phosphorylcholine (AGEPC) physiologic activity and of IgE anaphylaxis in the rabbit, PGI2 was employed as an inhibitor of in vivo platelet function. Intravenous infusion of PGI2 (1 to 2 micrograms/kg/min) inhibited the AGEPC-induced decrease in dynamic compliance, increase in total pulmonary resistance, and transient decrease in tidal volume, but the right ventricular hypertension, bradycardia, and apnea were unaffected. Although PGI2 itself produced a marked systemic hypotension, AGEPC still induced a bimodal hypotensive response. Documentation that platelet function was inhibited by PGI2 included partial inhibition of AGEPC-induced thrombocytopenia, abrogation of platelet secretion (as assessed by plasma platelet factor 4 levels), and inhibition of ex vivo platelet aggregation. The AGEPC-induced leukopenia was not affected. In another group of rabbits, chlorpheniramine pretreatment inhibited the lung mechanical changes induced by AGEPC but did not affect the ventilatory or circulatory alterations, indicating that the lung mechanical alterations (but not any of the other alterations) are mediated by platelet-secreted histamine acting via H1 receptors. In IgE-producing rabbits intravenously challenged with antigen, PGI2 had no effect on any of the physiologic alterations, despite substantial inhibition of platelet secretion. From these results, together with previous platelet depletion studies, we conclude that AGEPC may be a significant mediator of the circulatory alterations and apnea of rabbit IgE anaphylaxis by platelet-independent mechanisms, but neither AGEPC nor platelets appear to be important in mediating the anaphylactic lung mechanical alterations.

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.

Differential effects of platelet depletion on the physiologic alterations of IgE anaphylaxis and acetyl glyceryl ether phosphorylcholine infusion in the rabbit.

Intravenously administered acetyl glyceryl ether phosphorylcholine (AGEPC) induced all of the respiratory and circulatory alterations observed during IgE anaphylaxis in the rabbit. Prior platelet depletion, however, had differential effects on these two physiologic responses. The AGEPC-induced increase in total pulmonary resistance and decrease in dynamic compliance were abrogated by prior platelet depletion, whereas these lung mechanical changes occurring as part of an IgE anaphylactic response after intravenous antigen challenge were unaffected by platelet depletion. The apneic episode observed in both the AGEPC and antigen-induced response was unaffected by platelet depletion, and the brief period of rapid shallow breathing of the AGEPC response was diminished to that characteristically seen in the anaphylactic response of both platelet-intact and platelet-depleted rabbits. Prior platelet depletion had little effect on right ventricular hypertension, bradycardia, and systemic hypotension of either the AGEPC or the anaphylactic responses. Thus, AGEPC induced lung mechanical alterations via platelet-dependent mechanisms and ventilatory and circulatory alterations by mechanisms largely independent of circulating platelets. These findings were consistent with the possibility that AGEPC released into the blood stream during IgE anaphylaxis may mediate the circulatory and ventilatory alterations but not the lung mechanical alterations of the anaphylactic response.

Respiratory and circulatory alterations induced by acetyl glyceryl ether phosphorylcholine, a mediator of IgE anaphylaxis in the rabbit.

We examined the physiologic alterations induced in the rabbit by an acetyl glyceryl ether phosphorylcholine (AGEPC), a synthetic compound identical to rabbit basophil-derived platelet-activating factor. Intravenous administration of AGEPC led to a brief period of rapid, shallow breathing, a transient apnea, a decrease in dynamic compliance, and an increase in total pulmonary resistance. Circulatory alterations included brief bradycardia, increase in right ventricular pressure, and systemic hypotension. At a dose of 0.6 microgram/kg, AGEPC produced physiologic alterations both qualitatively and quantitatively indistinguishable from those which characterize IgE anaphylaxis in the rabbit. Mortality was also similar. After recovery to prechallenge baseline values, subsequent doses of AGEPC resulted in attenuated responses with respect to many of the physiologic alterations. Thrombocytopenia, leukopenia, and platelet secretion (as assessed by release of platelet factor 4 into the plasma) were also part of the response to AGEPC, further extending the similarity of this response to IgE anaphylaxis. Because AGEPC has been shown previously to be released into the circulation during IgE anaphylaxis, our results provide strong evidence that AGEPC is an important mediator of this acute allergic reaction in the rabbit.