The first two important variables of each model were selected according to the ranking of importance, and the final identified key genes for RA immune heterogeneity were IFNG, IL7R, CCR7, KLRB1, CXCL9, CXCL13, SELL, and PTPRC (Fig. 3B–E). Here, KLRB1 is linked to rheumatoid arthritis.