Interleukin 17A and F and asthma in Saudi Arabia: gene polymorphisms and protein levels.

BACKGROUND Asthma is a multifactorial disorder, and both genetic and environmental factors contribute to its development. We investigated the possible association between asthma and 5 single-nucleotide polymorphisms (SNPs) in the interleukin 17 (IL17) gene--rs17880588 (G/A) and rs17878530 (C/T) in IL17A and rs763780 (T/C), rs11465553 (T/C), and rs2397084 (G/A) in IL17F--and compared levels of the proteins IL17A and IL17F in asthma patients with those of controls. PATIENTS AND METHODS The study group included 100 asthma patients and 102 ethnically matched controls. Genotyping was performed on purified DNA using reverse transcriptase-polymerase chain reaction with specific primers and probes. Levels of IL17A and IL17F were measured in plasma using enzyme-linked immunosorbent assay. RESULTS Genotyping showed that AG heterozygotes of rs17880588 in IL17A were significantly more common in the control group than among the asthma patients (P < .05); no significant associations were observed for any of the other SNPs examined. Levels of IL17A and IL17F were both higher in asthma patients (IL17A, 2.242 [0.099] vs 2.752 [0.287] pg/mL; IL17F, 236.01 [38.28] vs 700 [201.078] pg/mL). The difference was statistically significant for IL17F (P = .025, t test). Levels of IL17A and IL17F were positively and significantly correlated in the asthma patients CONCLUSION Of all the SNPs analyzed, only rs17880588 showed a significant association with asthma in the Saudi population we studied. Levels of IL17A and IL17F were significantly upregulated in the asthma patients. The morphology of IL17F appeared to affect expression levels.