Elevated anti-streptococcal mitogenic exotoxin Z-2 (SMEZ-2) antibody in patients with active ulcerative colitis (UC) who had skewed T cell receptor β-chain 4 (TCRBV4). (a) The anti-SMEZ-2 titre was significantly higher in patients with skewed TCRBV4 compared with healthy volunteers (P = 0·0305, by Mann–Whitney U-test). (b) The correlation of the percentage of TCRBV4 with anti-SMEZ-2 titre (n = 23, ρ= 0·606, P = 0·0045, by Spearman's rank correlation). The anti-streptolysin-O (ASO) level (c) also showed significant correlation with the anti-SMEZ-2 titre (n = 27, ρ= 0·352, P = 0·0149, by Spearman's rank correlation test), but no correlation with anti-toxic shock syndrome toxin 1 (TSST-1) titre was seen.