CD4 and rheumatoid arthritis: In addition, an RA-associated locus tagged by rs13119723, an SNP mapping to an intron of the gene of unknown function KIAA1109 and containing multiple variants in LD spanning over 500 Kb, was fine mapped to a single SNP mapping to a H3K4me3 peak specific to CD4 + Treg cells thought to be involved in the regulation of IL2 expression.