Читать книгу Handbook of Diabetes - Rudy Bilous - Страница 48

The increasing incidence of atopy as well as early‐onset type 1 diabetes in Western societies may be a consequence of a lack of exposure to common pathogens such as helminth worms (so called ‘old friends’), or lactobacilli (microflora). Chronic exposure might include a more tolerant T cell response to antigens, while a cleaner, more sterile early environment would result in an exaggerated response in subsequent months or years. Some of the associated factors listed in Table 6.3 would support this hypothesis.

Pregnancy is thought to have a Th2 lymphocyte orientation whilst early environmental antigen exposure stimulates Th1 responses. The first line immune response in children comprises immature dendritic cells which are primed to respond to specific antigens, and they also carry innate pattern recognition receptors that bind to viral or bacterial cell surfaces. T‐cell receptors are highly cross reactive so an immune response to common allergens or self antigens might be activated by infection. It was originally thought that an imbalance in Th1 and 2 cells would lead to a different balance in cytokine release predisposing to either autoimmunity (Th1 predominance) or allergy (Th2 predominance). However, this construct has not been supported by the observation that helminth (pinworm) exposure actually leads to a more pronounced Th2 response but lower rates of atopy. Thus, the hygiene hypothesis, despite supportive associative data, remains unproven.