Relative expression of the 2 Cytotoxic T lymphocyte Antigen-4 (CTLA-4) transcripts, the full length form and the spliced form in peripheral blood lymphocytes of patients with spondylarthropathies (SpA) and patients with rheumatoid arthritis (RA). The full length form (gray bars) contains four exons and codes for the CTLA-4 molecule expressed at the cell membrane while the spliced form (open bars) contains three exons, lacks the transmembrane region and codes for the soluble CTLA-4 molecule . Results (mean ± standard error of the mean) are obtained using the ΔΔCt method and expressed as a fold change of each CTLA-4 transcript comparative with the reference obtained with the pool of 15 healthy donor PBL. Wilcoxon test was used to compare the relative production of the full length and the spliced form in patients with SpA and in patients with RA (*** P < 0.005). NS = not significant.