The difference in CXCR5 expression between RA patients and non-RA patients was unlikely to be due to differences in the relative amount of cDNA produced by different RT reactions since the PCR reactions were normalized using the ribosomal gene L27. RT-PCR showed that the difference between RA patients and non-RA patients was less marked for CXCR2 and CXCR4 than for CXCR5 (data not shown). Here, CXCR4 is linked to rheumatoid arthritis.