Primary sensitization to inhalant allergens

Preterm birth reduces the incidence of atopy in adulthood

BACKGROUND

Immunologic pathways are primed in early life. Preterm birth can influence this process and thereby affect whether a person will have atopy later in life. Previous studies on the effects of preterm birth on atopy in adulthood have been inconclusive and limited to children or subjects born moderately preterm.

OBJECTIVE

Our aim was to compare the incidence of atopy among young adults who were born preterm and at very low birth weight (≤ 1500 g) with that of term-born young adults (control subjects).

METHODS

The study comprised 166 adults who were born preterm and at very low birth weight and 172 control subjects, all of whom were from the Helsinki Study of Very Low Birth Weight Adults. We assessed atopic predisposition at ages 18 to 27 years using skin prick tests for 6 common aeroallergens and measurements of serum concentrations of total IgE and 3 types of allergen-specific (cat, birch, and timothy) IgE. We asked the subjects whether they had been given a diagnosis of asthma or allergic rhinitis or had atopic eczema and analyzed data by using logistic or linear regression, adjusting for potential confounding factors.

RESULTS

The risk for having at least 1 positive reaction on a skin prick test was reduced (adjusted odds ratio, 0.43; 95% CI, 0.23-0.79, P = .007), and the concentration of cat-specific IgE was less (25% less; 95% CI, 43% to 2.3% less; P = .033) in sera from very-low-birth-weight subjects compared with that seen in sera from control subjects. Within the very-low-birth-weight group, those born at an earlier gestational age were less likely to have positive skin prick test reactions (adjusted odds ratio for 1 week, 0.82; 95% CI, 0.68-0.98, P = .029) and less likely to have high levels of allergen-specific IgE. Cumulative incidences of atopic disease were similar between adults of very low birth weight and control subjects.

CONCLUSIONS

Young adults born prematurely and at very low birth weight have a lower incidence of atopy than adults who were born full term. This finding supports the hypothesis that the risk for atopy is determined during early stages of development.

Maturation of cytokine-producing capacity from birth to 1 yr of age

Little is known about the immunologic maturation in the early stages of life. The aim of this study was to investigate maturation of immune system from birth to 1 yr of age and to compare immune functions between mothers and their children. Also the effect of atopy to the immune responses of children was examined. Cord blood samples (n = 228) and peripheral blood samples of children (n = 200) and their mothers (n = 208) 1 yr after birth were collected. Whole blood samples were stimulated for 24 and 48 h with Staphylococcal enterotoxin B (SEB), lipopolysaccharide (LPS) and the combination of phorbol ester and ionomycin (P/I). Production of TNF-alpha, IFN-gamma, IL-5, IL-8 and IL-10 was determined using ELISA. Significant mother-to-child correlation was detected in cytokine-producing capacity at the age of 1 yr. TNF-alpha (P/I, SEB and LPS stimulation), IFN-gamma (P/I and SEB), IL-5 (P/I and SEB) and IL-10 (P/I, SEB and LPS) producing capacity increased from birth to 1 yr of age. In general, stimulated cytokine responses were higher in mothers' than in children's blood samples, except in the case of P/I and LPS-stimulated IL-8, which were highest at birth. Maternal inhalation atopy was associated with increased cord blood IL-5 (24 and 48 h) and IL-10 (48 h) production following P/I stimulation. Also children of food atopic mothers expressed elevated cord blood IL-10 (48 h, P/I) responses and decreased IFN-gamma/IL-5 ratio (24 h, P/I). In addition, the production of IFN-gamma (24 and 48 h, P/I) and the IFN-gamma/IL-5 ratio (24 h and 48 h, P/I) at the age of 1 yr was lower among children with food atopic mothers. In conclusion, our results suggest that both adaptive and innate immune responses increase from birth to 1 yr of age, but are still weak in comparison to adult responses. Cytokine responses of children begin to correlate with those of their mothers during the first year of life. Although only few associations were observed between atopy and cytokine-producing capacity, our results suggest that children of atopic mothers express T(h)2-polarized cytokine pattern.

Prevalence of asthma among Chinese adolescents living in Canada and in China

BACKGROUND

Studies of the prevalence of asthma among migrating populations may help in identifying environmental risk factors.

METHODS

We analyzed data from Vancouver, Canada, and from Guangzhou, Beijing and Hong Kong, China, collected during phase 3 of the International Study of Asthma and Allergies in Childhood. We subdivided the Vancouver adolescents according to whether they were Chinese immigrants to Canada, Canadian-born Chinese or Canadian-born non-Chinese. We compared the prevalence of asthma and wheezing among Chinese adolescents born in Canada, Chinese adolescents who had immigrated to Canada and Chinese adolescents living in China.

RESULTS

Of 7794 Chinese adolescents who met the inclusion criteria, 3058 were from Guangzhou, 2824 were from Beijing, and 1912 were from Hong Kong. Of 2235 adolescents in Vancouver, Canada, 475 were Chinese immigrants, 617 were Canadian-born Chinese, and 1143 were Canadian-born non-Chinese. The prevalence of current wheezing among boys ranged from 5.9% in Guangzhou to 11.2% in Canadian-born Chinese adolescents. For girls, the range was 4.3% in Guangzhou to 9.8% in Canadian-born Chinese adolescents. The prevalence of ever having had asthma ranged from 6.6% to 16.6% for boys and from 2.9% to 15.0% for girls. Prevalence gradients persisted after adjustment for other environmental variables (odds ratios for ever having had asthma among Canadian-born Chinese compared with native Chinese in Guangzhou: 2.72 [95% confidence interval 1.75-4.23] for boys and 5.50 [95% confidence interval 3.21-9.44] for girls; p < 0.001 for both). Among Chinese adolescents living in Vancouver, the prevalence of ever wheezing increased with duration of residence, from 14.5% among those living in Canada for less than 7 years to 20.9% among those living their entire life in Canada. The same pattern was observed for the prevalence of ever having had asthma, from 7.7% to 15.9%.

INTERPRETATION

Asthma symptoms in Chinese adolescents were lowest among residents of mainland China, were greater for those in Hong Kong and those who had immigrated to Canada, and were highest among those born in Canada. These findings suggest that environmental factors and duration of exposure influence asthma prevalence.

Feeding a formula supplemented with long chain polyunsaturated fatty acids modifies the "ex vivo" cytokine responses to food proteins in infants at low risk for allergy

Long chain polyunsaturates (LCP) status during the early neonatal period is associated with a reduced risk of atopic symptoms and later allergies. In this study, we characterized the immune response of low-risk, term, formula-fed infants randomized at <or=14 d of age to standard term formula (Formula) or formula containing LCP (Formula+LCP) for 4 wks. Infants exclusively fed human milk were included for comparison. Peripheral blood was collected at 14 and 42 d of age, and lymphocyte phenotype, proliferation, and cytokine production (IL-2, IL-4, IL-6, IL-10, IL-12, IFN-gamma, TNF-alpha, TGFbeta) were assessed after incubation with beta-lactoglobulin (BLG) and soy protein (SOY). Lymphocyte proliferation did not differ between groups. Compared with human milk-fed infants at 2 wks, formula-fed infants produced more TNF-alpha and IFN-gamma and had more cells expressing ICAM-1 (CD54) after incubation with BLG and SOY (p < 0.05). At 6 wks of age, infants fed Formula+LCP produced more TNF-alpha with SOY (3.2-fold) and IFN-gamma (3.3-fold) with BLG compared with infants fed Formula (p < 0.05). In conclusion, low-risk term infants fed formula before 14 d of age produced more TNF-alpha and IFN-gamma in response to food proteins. Feeding Formula+LCP for 4 wks maintained the higher TNF-alpha and IFN-gamma response to these food proteins.

Think globally, breathe locally

Why the worldwide health impact of air pollution on young children begins in our neighbourhoods

Ontogeny of the Allergic Inflammatory Response

The ability to produce allergic responses begins early in fetal life along with the development of other elements of the immune system. Among the most interesting questions related to the development of allergic disease are whether the fetus in utero commonly is exposed to sufficient allergen to induce IgE production and how much the mother's immune responses affect the developing fetal immune system. After birth, it seems that many factors, including the frequency and severity of infections and the timing and intensity of allergen and animal exposures, continue to influence immune development.

Fish oil supplementation in pregnancy modifies neonatal progenitors at birth in infants at risk of atopy

Dietary n-3 polyunsaturated fatty acids (PUFA) may represent a mode of allergy prevention. Cord blood (CB) CD34+ hemopoietic progenitors are altered in infants at risk of atopy. We therefore studied the effects of dietary n-3 PUFA supplementation during pregnancy on numbers and function of progenitors in neonates at high risk of atopy. In a double-blind study, atopic, pregnant women were randomized to receive fish oil capsules or placebo from 20 wk gestation until delivery. At birth, CB CD34+ cells were isolated and analyzed by flow cytometry for expression of cytokine (IL-5Ralpha, IL-3Ralpha, granulocyte/macrophage colony-stimulating factor Ralpha) or chemokine (CXCR4 and CCR3) receptors. CB cells were also cultured in methylcellulose assays for eosinophil/basophil colony-forming cells. At age 1 y, infants were clinically assessed for atopic symptoms and skin tests. Percentages of CB CD34+ cell numbers were higher after n-3 PUFA than placebo. Co-expression of cytokine or chemokine receptors on CD34 cells was not altered by n-3 PUFA supplementation. However, there were significantly more IL-5-responsive CB eosinophil/basophil colony forming units (Eo/B-CFU) in the fish oil, compared with the control, group. Overall, there was a positive association between CD34+ cells and IL-5-responsive Eo/B-CFU in CB and 1 y clinical outcomes, including atopic dermatitis and wheeze. Dietary n-3 PUFA supplementation during pregnancy in atopic mothers alters infant cord blood hemopoietic progenitor phenotype. This may have an impact on development of atopic disease.

Cat allergen-induced cytokine secretion and Fel d 1-immunoglobulin G immune complexes in cord blood

BACKGROUND

We have recently obtained evidence for the presence of immune complexes (IC) in cord blood from allergic and non-allergic mothers. Such complexes could conceivably provide the fetus with the initial trigger for the priming of the T cell system already in utero.

OBJECTIVE

To relate the presence of Fel d 1-IgG IC to T cell cytokine production in cord blood mononuclear cells (CBMCs) after stimulation with cat allergen.

METHODS

CBMC obtained from babies of 15 allergic and 22 non-allergic mothers were cultured in the presence of cat allergen. The production of IFN-gamma, IL-5, IL-10 and IL-13 was determined by ELISA. Furthermore, IgG1 and IgG4 antibodies to cat allergen in cord blood samples were measured by ELISA. A more sensitive ELISA was used to measure Fel d 1-IgG IC.

RESULTS

The prevalence and levels of IC were similar in cord blood from children of allergic and non-allergic mothers. The production of IL-5, IL-10. IL-13 and IFN-gamma by CBMC was not influenced by maternal atopy, but IFN-gamma was less commonly detected in samples with IC. There was no association between the presence of IC and any other cytokines. The levels of IgG1 and IgG4 antibodies were similar in both groups, and tended to be associated with the presence of IC.

CONCLUSION

Immune complexes in cord blood may represent a normal mechanism for inducing primary immune responses, as the responses in babies from allergic and non-allergic mothers were largely similar. Low levels of IFN-gamma seems to be related with the presence of IC in cord blood.

Exposure to birch pollen in infancy and development of atopic disease in childhood

BACKGROUND

The relationship between early allergen exposure, sensitization, and development of atopic disease remains controversial. In 1993, extremely high levels of birch pollen were recorded in Stockholm, Sweden, creating the unique opportunity to study children with different exposures during infancy.

OBJECTIVE

We sought to assess the influence of early high-dose exposure to an inhalant allergen (birch pollen) on sensitization and development of atopic disease in children.

METHODS

A total of 583 children with atopic heredity born in Stockholm in February through April 1992, 1993, or 1994 were investigated at age 4.5 to 5 years. The children were examined and underwent skin prick testing with inhalant and food allergens. IgE antibodies (RAST) against birch pollen and recombinant birch pollen allergen (rBet v 1) were analyzed in serum.

RESULTS

The children born in 1993 (high-dose exposure at 0-3 months) were more often sensitized (ie, positive skin prick test response) to birch pollen than the children born in 1994 (low-dose exposure; 17.8% and 8.8%, respectively; odds ratio [OR], 2.4; 95% CI, 1.2-4.6). A tendency in the same direction was seen for children born in 1992 (high-dose exposure at 12-15 months; OR, 1.7; 95% CI, 0.9-3.2). The results were supported by the RAST analyses. The prevalence of bronchial asthma, allergic rhinoconjunctivitis, and atopic dermatitis did not differ between the birth-year groups. However, the prevalence of pollen- and animal dander-induced allergic asthma was increased in the children born in 1993 (OR, 2.6; 95% CI, 1.2-5.6). An interaction between early high-dose exposure to birch pollen and cat in the household was suggested for sensitization to cat (P =.06).

CONCLUSION

Exposure to high levels of birch pollen in infancy increases the risk of sensitization to the same allergen, as well as the risk of allergic asthma.