Search

The central role of T regulatory cells in the responses against harmless environmental antigens has been confirmed by many studies. Impaired T regulatory cell function is implicated in many pathological conditions, particularly allergic diseases. The "hygiene hypothesis" suggests that infections and infestations may play a protective role for allergy, whereas environmental pollutants favor the development of allergic diseases. Developing countries suffer from a variety of infections and are also facing an increasing diffusion of environmental pollutants. In these countries allergies increase in relation to the spreading use of xenobiotics (pesticides, herbicides, pollution, etc.) with a rate similar to those of developed countries, overcoming the protective effects of infections. We review here the main mechanisms of non-self tolerance, with particular regard to relations between T regulatory cell activity, infections and infestations such as helminthiasis, and exposure to environmental xenobiotics with relevant diffusion in developing countries., (Copyright © 2010 Elsevier B.V. All rights reserved.)

The aim of the study was to assess the seasonal variability of non-specific bronchial reactivity (NSBR) evaluated with methacholine in asthmatic farmers allergic to pollens. Twenty farmers (16 male and four female) with allergy to pollens, e.g. 'Graminae' and 'Parietaria', entered the study. None of the patients had been previously treated with specific immunotherapy. Patients underwent a methacholine challenge at the first visit and then in the subsequent seasons. Four groups of tests were obtained according to the period when the challenge was performed. Group 1: challenges performed in December, January and February; group 2 in March, April and May; group 3 in June, July and August; group 4 in September, October and November. PD20 values were expressed as the natural logarithm of the cumulative dose of methacholine causing at least a 20% fall in FEV1. Bronchial hyperreactivity was highest in summer, followed by spring and autumn; in winter it was much lower. Multiple group analysis (ANOVA) showed statistically significant differences between the groups (P < 0.01). When the groups were compared individually, statistically significant differences existed only between group 1 (winter) and each of the other groups, respectively 2 (spring) (P = 0.02), 3 (summer) (P = 0.004) and 4 (autumn) (P = 0.02). The results underlined the importance of allergic inflammation in determining changes in NSBR. In the region where the study was carried out (central Italy), the grass and Paretaria pollination lasts from March to November. Therefore, farmers had a progressive increase in NSBR from spring to summer and a decrease in fall as a consequence of the varying pollen concentration in different seasons. The level of allergen exposure is, in fact, the main factor that determines the severity of bronchial inflammation, thus affecting NSBR.

We assessed the infiltration of CD45RO+ cells in conjunctival biopsies of fifteen subjects affected by seasonal allergic conjunctivitis by means of immunohistochemistry. Correlations between infiltration of CD45RO+ cells and serum and mucosal indices of eosinophilic activation were investigated. The study was performed in autumn and all selected patients showed <> also in absence of sensitising pollens. Fifteen healthy subjects were used as controls. The semi-quantitative count of CD45RO+ cells in biopsy specimens demonstrated that positive cells were higher in allergic patients than in controls (p < 0.001) and EG2+ eosinophils were present only in biopsies of allergic patients. Furthermore, a statistically significant positive correlation (r = 0.73; p < 0.001) between CD45RO+ lymphocytes and EG2 positive eosinophils, was observed in the biopsies of allergic patients. Total serum IgE significantly correlated with CD45RO+ cells (r = 0.61; p < 0.02) and EG2+ eosinophils (r = 0.67; p < 0.01) in the conjunctiva. On the other hand serum ECP did not correlate with any histological and immunohistochemical parameters in the conjunctival biopsies. The present study shows that mild symptoms in SCA patients out of pollen season are associated with inflammation of the conjunctiva as shown by an increased number of CD45RO and EG2 positive cells.