الفهرس 
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Abstract
Chronic periodontitis is a complex inflammatory disease, which is a major cause of tooth loss. The risk for chronic periodontitis is influenced by environmental and genetic factors. Cytokine gene polymorphisms may have an impact on the susceptibility to and progression of chronic periodontitis. IL-4 is considered an anti-inflammatory cytokine because it possesses important functions in the modulation of B cells. IL-4 down-regulates macrophage function and inhibits the secretion of prostaglandin E2 (PGE2) and cytokines by macrophages. IL-4 inhibits the secretion of proinflammatory cytokines such as IL-1 and -6 and tumor necrosis factor (TNF).
The present study was conducted to investigate the association between the IL-4 -590 C/T polymorphism and chronic periodontitis in a sample of Egyptians.
80 subjects were recruited for the study from the patient pool at the dental clinics of the faculty of dentistry, Alexandria University. All subjects were non-smokers, Egyptians and in good general health within the age range of 20-60 years of age. Subjects were divided into two main groups:
• Chronic periodontitis patients group (n = 40, 11 males and 29 females with mean age of 36.03 ± 1.27 years).
• Healthy controls group (n = 40, 19 males and 21 females with mean age of 35 ± 6.5 years).
The diagnosis was made on the basis of standardized clinical and radiographic criteria.
Genomic DNA was obtained from peripheral blood leukocytes by the conventional “salting out” method. Genotyping of the promoter -590 C/T polymorphism of IL-4 gene was carried out using polymerase chain reaction- restriction fragment length polymorphism (PCR-RFLP) analysis. Genotype and allele frequency distributions among the periodontitis patients and controls were compared using chi squared and Monte Carlo tests (p<0.05).
The results of this study showed statistically significant association between chronic periodontitis and -590 C/T polymorphism of IL-4 gene. In the control group, there was a strong predominance of allele C. The frequency of allele T was higher in chronic periodontitis patients (50 %) compared to controls (16.3 %). Moreover, the differences in allele frequency distribution between both groups were found to be statistically significant.