It was shown in this study that for RA and SLE patients with co-infection with HBV, the levels of IgG, IgA, IgM and CD8+ were significantly lower after treatment, while CD3+, CD4+ and CD4+/CD8+ were significantly higher, indicating that in RA and SLE patients with co-infection with HBV, their immunoglobulin and T lymphocyte subsets recovered with the improvement of their disease. The gene discussed is CD8A; the disease is rheumatoid arthritis.