While in those of PG, rag-3 (60.87%), rag-4 (39.13%), rag-1(30.43%) were much higher than those in CG (only rag-2 positive); Similar to those of periodontitis group, in those of OG, the proportion of rag genotypes were: rag-3 44.83%, rag-4 37.93%, rag-2 20.69%; but in CG: only one case of rag-2 (14.29%) was detected. Here, RAG2 is linked to periodontitis.