| Popis: |
The prevalence of asthma and atopic disease in general, has been increasing in the past forty years, with the UK having one of the highest rates in the world. There have been many theories proposed to explain these increases, but no definitive answer has been found, as yet. Dietary hypotheses suggest that the recent increases in asthma and atopic disease are a consequence of changing dietary lipid intake and lor decreasing dietary antioxidant intake. This hypothesis has been supported by local work, which- has demonstrated that a maternal diet deficient in some antioxidants may influence childhood Th-cell differentiation towards the Th2 phenotype in vitro. Previously, it was thought that Th1 cells regulated Th2 cells. However, it is now thought that Th2 responses may be regulated by other cells, such as Tregulatory cells, (Tr-cells) that have the potential to be involved in the immunopathogenesis ofasthma and atopic disease.. The aims of this project were to characterise -the effects of direct antioxidant and lipid supplementation on umbilical cord blood Th-cells in vitro, and to determine whether the proliferative and cytokine responses of cord blood mononuclear cells, (CBMC) after stimulation with allergens, were mediated through regulatory T-cells. Supplementation with vitamin E, vitamin C or a.-linolenic acid was performed on 135 neonatal cord blood samples. Cell proliferation was quantified 5,6 and 7 days, after stimulation with mitogen, control antigens and allergens, by incorporation of 3H-thymidine into triplicate lOO~1 aliquots drawn from the cultures. Production of the Th1 and Th2 cytokines IFN-y and IL-4, and the regulatory cytokines IL-IO and TGF-13 were measured by a sensitive cellular ELISA adapted for use with CBMC. Flow cytometry was used to identify the phenotype ofTr-cells, by staining for surface antigens and intracellular cytokines. This project has demonstrated that direct supplementation of cord blood Th-cells with vitamin E, vitamin C and a.-linole,nic acid, does influence proliferative and cytokine responses to control stimuli and allergens. Specifically, these nutrients are associated with a general suppression of CBMC proliferative responses to control stimuli and the allergen house dust mite. In contrast, the two vitamins are associated with an increase in CBMC proliferative responses to the allergen, timothy grass pollen. Supplementation is also associated with a general decrease in IFN-y and TGF-13 secretion, with varying effects on IL-IO and IL-4 secretion. This work has also confirmed the presence of functional Tr-cells in neonatal blood at birth. The phenotype of these Tr-cells varies, with cells expressing various combinations and numbers of the three Tr-cell markers; CD25+high, Foxp3 and IL-IO. Allergen stimulation appears to induce Tr-cells in the greatest amounts. In conclusion, this project has demonstrated, for the first time, that direct supplementation of CBMC, with vitamins E and C, and the PUFA, a-linolenic acid, does influence cord blood Th-cell proliferative and cytokine responses to control stimuli and allergens, altering the balance of Th-cell subsets, and suggests that manipulation of maternal diet during pregnancy could modulate neonatal immune responses to allergens and the development of asthma and atopic disease. It has also confirmed the presence of functional Tr-cells in neonatal blood at birth, with variability in numbers between individuals, upon allergen stimulation. The variability in Tr-cell activity associated with allergen stimulation may be linked to the development ofatopic disease in later life. |
