الفهرس 
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Abstract
Allergic diseases are an important cause of morbidity in developed countries where they are the commonest cause of chronic disease in childhood. Epidemiological research has therefore focused on identifying the possible environmental factors that are associated with increased allergy risk. Helminth infections are one of the factors identified in this context. There is evidence to suggest that helminth infections are sustained through a parasite-induced immunemodulatory network. This, in turn, may have a down-regulatory effect on the risk of developing allergic disease. So, this work was designed to investigate the association between parasitic infections and allergic diseases with special emphasis on; allergic bronchial asthma, allergic rhinitis and allergic eczema through analysis of the expression of Toll like Receptor 2 on peripheral blood monocytes and to compare that expression in different study groups.
The study was conducted on 348 patients who had attended the Chest, Otolaryngology and Dermatology Outpatient Clinics of Suez Canal University Hospital or its affiliated primary health care units in Ismailia, Egypt, from the period of January to December 2010. Two study groups were selected according to the physician’s diagnosis; group I (174): patients with allergic diseases and are further subdivided into 3 subgroups: group I-a; patients suffering from bronchial asthma, group I-b; patients suffering from allergic rhinitis, group I-c; patients suffering from allergic eczema and group II (174): as a healthy control group. Patients and control groups were subjected to the following: (1) full history taking, (2) thorough clinical examination, (3) parasitological investigation stool, urine and blood film examination, and (4) blood sample investigation for Toll like Receptor 2 (TLR-2) expression and activity.
This study showed that the overall prevalence of pathogenic parasitic infections among patients of the study population was 18.7 %. Prevalence of pathogenic parasitic infections among allergic patients was 12.1% (5.8% among allergic asthma patients, 4.6% among allergic eczema patients and 1.7% among allergic rhinitis patients) while prevalence of pathogenic parasitic infections among non allergic patients was 25.3%.
Parasitological examination among the allergic patients showed that 13.9 % had a positive stool/urine examination for parasitic infections, while 86.1% had a negative stool/urine examination for parasitic infections. In non-allergic patients, 22.3 % had a positive stool/urine examination for parasitic infections, while 77.7% had a negative stool/urine examination for parasitic infections.
Regarding the mean fluorescence intensity for TLR2 among the allergic non-infected patients which showed that most of them (90.8%) had moderate increase in intensity compared to 100% of non- allergic non-infected patients who showed mild level of intensity. This difference was statistically non-significant.
While, the mean fluorescence intensity for TLR2 among the allergic infected patients showed that most of them (85.7%) showed moderate level of fluorescence intensity compared to 100% of non-allergic non- infected patients. This difference was statistically significant.
On the other hand, the mean fluorescence intensity for TLR2 among the non-allergic infected patients showed that most of them (65.9 %) showed moderate level of fluorescence intensity compared to 100% of non-allergic non- infected patients. This difference was statistically significant.
In conclusion, this study reveals a negative association between helminths infection and different allergic diseases and a possible interaction between parasitic infections, TLR signaling and the immune response, which may explain the mechanism of parasitic infection induced immune-tolerance. However, a causal association between parasitic infection and allergy remains to be proven.