IL4 and periodontitis: Meta-analysis of the IL-4 -33C/T showed no association between the polymorphism and periodontitis susceptibility (T versus C: OR = 1.01, 95% CI = 0.69–1.47; TT versus CC: OR = 1.15, 95% CI = 0.57–2.34; CT versus CC: OR = 0.83, 95% CI = 0.61–1.13; TT + CT versus CC: OR = 0.92, 95% CI = 0.65–1.30; TT versus CC + CT: OR = 1.15, 95% CI = 0.57–2.34).