Is deficiency of interferon gamma production by allergen triggered cord blood cells a predictor of atopic eczema?

Inhalant allergen-specific T-cell reactivity is detectable in close to 100% of atopic and normal individuals: covert responses are unmasked by serum-free medium

BACKGROUND

It is widely held that in vitro T cell responses to allergens are more prominent in atopic than in normal individuals, though this conclusion is based upon culture techniques which fail to detect proliferative responses in a significant minority of atopics and many normals.

OBJECTIVES

Study allergen-specific proliferative responses of T cells cultured in serum-free medium (SFM). Examine associations between atopic status, age and T cell reactivity.

METHODS

Initially, peripheral blood mononuclear cells were stimulated with allergens or antigens in SFM, and compared with cells cultured in RPMI + 10% fetal calf serum or human AB serum. Subsequently, T cell reactivity was studied in 34 adults (20-49 years), 27 children (2-13 years), and 19 infants (< or = 10 weeks) using SFM alone.

RESULTS

Compared with serum-supplemented medium, SFM enhanced net T cell proliferation, both in bulk culture and when cloning at limiting dilution. In many subjects, SFM unmasked T cell reactivity to allergens which was not otherwise evident, and lowered the threshold allergen levels required for in vitro T cell triggering. For most allergens, T cell proliferative responses did not differ between adults who had specific IgE, and those who did not. The most vigorous responses observed were to ubiquitous inhalant allergens, which stimulated T cells from close to 100% of adults and children, and over 60% of infants. In contrast, responses to the 'vaccine' antigen tetanus toxoid were completely absent in the latter age group, but present in the majority of adults and children.

CONCLUSIONS

These findings suggest that the extent of active T cell recognition of environmental allergens has been hitherto underestimated, and further that these responses may frequently be initiated in very early life. Additionally, these findings reinforce the notion that qualitative (as opposed to quantitative) variations in specific T cell reactivity ultimately determine allergen responder phenotype.

Serum levels of interleukin-4, soluble CD23 and IFN gamma in relation to the development of allergic disease during the first 18 months of life

Serum levels of Interleukin (IL)-4, Interferon (IFN)-gamma and soluble CD23 (sCD23) were analysed in a prospective study of 64 infants who were monitored from birth to 18 months of age. The findings were related to family history of atopy and the development of allergic disease in the infants. Low levels of IL-4 were detected in 10 of 63 cord blood samples (median 0.14 and range 0.32 micrograms/l). The levels then increased, both in health and atopic infants, reaching a peak at either 6 or 9 months and then decreased up to 18 months of age. The children who developed atopic disease during the first 18 months of life had significantly higher IL-4 median levels than those who did not, i.e. 0.24 (range 0.40) vs < 0.10 microgram/l at 3 months, (P < 0.001), 0.40 (range 0.95) vs 0.13 (0.19) microgram/l at 6 months (P < 0.01), 0.46 (range 0.78) vs 0.10 (0.24) microgram/l at 9 months (P < 0.001) and 0.30 (range 1.38) vs 0.10 (0.36) microgram/l at 18 months (P < 0.001). The IFN gamma levels were below the detection level, i.e. < 100 ng/l in all but 49 of the 196 serum samples that were analysed. There was no significant relationship with clinical outcome, nor with S-IgE levels. Soluble sCD23 levels increased in the infants with age. There was no association with either atopic disease, family history of allergic disease or IgE antibody levels. In conclusion, IL-4 levels in serum, but not sCD23 and IFN gamma are associated with allergic disease in infancy.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduced interferon-gamma secretion in neonates and subsequent atopy

Low interferon-gamma (IFN-gamma) secretion has been found in individuals with active atopic disease. Whether this is a cause or result of the disease process is uncertain. Cord blood IFN-gamma secretion was examined in 35 neonates who were then prospectively followed up for 1 year for the development of atopic disease. Infants who developed either symptoms of atopic disease or a positive IgE-mediated skin prick test at 12 months of age produced significantly less IFN-gamma at birth compared with those who did not (p = 0.005). This reduced secretion of IFN-gamma at birth indicates that the defect in interferon secretion is a primary component of the atopic state rather than an effect of the disease process.