An Investigation into the Mechanistic Interplay between Th1 and Th2 Cells in Allergic Disease

The incidence of allergic disease has increased steadily in western countries over the past few decades. Substantial amounts of research have been geared toward elucidating the mechanisms whereby some people develop allergies and others do not. As with all development theories, the question revolves around the debate of genetics versus environment - attempting to determine the relative contribution from heredity and nurture in the development of an allergic phenotype. Heredity has long been identified as a risk factor for allergies. Children born of atopic (allergic disease attributed to heredity) parents are at an increased risk for developing atopy themselves. Consequently, genetics is obviously a component of the larger picture. However, rates and symptoms of allergy vary in prevalence both within and between countries inhabited by similar ethnic groups, suggesting that environment and lifestyle choices must play a part as well. The International Study of Asthma and Allergies in Childhood was founded in the last couple of years to establish a standardized methodology to investigate both prevalence and cause of allergies worldwide. This indicates that concern has risen enough over the possibility of an increased prevalence of allergic disease to warrant a systematic worldwide investigation to span a number of years. Developing countries have not seen the same increase in allergic diseases as the more 'westernized' countries, leading to the hypothesis that some aspect of the western lifestyle, such as smaller family size, altered diet, or decreased exposure to infectious diseases must account for this change.