For RA patients, B-lymphocytes are the predominant infiltrating cells, and the formation of synovial cell follicles is associated with the level of serum rheumatoid factor.14 As a 95 kD type I transmembrane glycoprotein, CD19 is the restricted antigen of B-lymphocytes, so the expression of CD19 corresponds to the level of B-lymphocyte.15 Moreover, CD28 molecule is the surface activation marker for B-lymphocytes by being related with their development and maturity. Here, CD28 is linked to rheumatoid arthritis.