Responses to mycobacterial antigens in patients with or without an immune-mediated inflammatory disease (IMID). The response to purified protein derivative (PPD) (a) and to culture filtrate protein (CFP)-10 (b) was analysed using the thymidine incorporation, (PKH)-26 dilution, and enzyme-linked immunosorbent spot (ELISPOT) assays in patients with (groups I, dotted boxes and II, gray shaded boxes) or without (groups III, diagonally lined boxes and IV, horizontally lined boxes) an IMID, and with previous or latent tuberculosis (groups II and IV) or without (groups I and III). Group I included 13, 12, and 12 patients with rheumatoid arthritis (RA), sponlylarthropathy (SA), and Crohn's disease (CD), respectively. Group II included 16, 13, and 2 patients with RA, SA, and CD, respectively. Twenty-one and 24 patients were studied in groups III and IV, respectively. The thymidine incorporation, (PKH)-26 dilution, and enzyme-linked immunosorbent spot (ELISPOT) assays were performed, with results expressed (mean ± standard error of the mean) as stimulation index (SI), fraction of proliferating cells (percentage), and number of interferon (IFN)-γ-producing cells per 106 cells. Comparisons for each assay were between groups I and II and between groups III and IV (*p < 0.05 and **p < 0.005, Mann-Whitney U test).