Flow cytometry showed that the absolute and relative numbers of CD56+ NK cells were significantly higher in RA-ILD (280.40 ± 180.51 cells/μl vs. 207.66 ± 148.57 cells/μl; 16.62 ± 8.56% vs. 12.11 ± 6.47%), whereas the proportion of T cells and CD4+ T cells was lower in peripheral blood of RA-ILD patients (69.82 ± 9.30%; 39.44 ± 9.87 cells/μl) than that in RA patients (74.45 ± 8.72%; 43.29 ± 9.10 cells/μl). This evidence concerns the gene CD4 and interstitial lung disease.