Objective: An intriguing link between gut and synovial inflammation exists in patients with spondyloarthropathy (SpA), illustrated by the high frequency of microscopically inflammatory gut lesions observed in these patients. We hypothesise that aberrant homing of mucosal T cells might play a role in the induction/perpetuation of arthritis in SpA. Here, we analyse the expression of the homing molecules alpha4beta7 and alphaEbeta7 on mucosal T cells from patients with ankylosing spondylitis (AS) and controls, in view of the critical role of these receptors in the homing of mucosal lymphocytes.
Methods: Colonic biopsy specimens were obtained from patients with AS (n = 23) and controls (n = 30). Biopsy specimens were immunostained, treated for extraction of intraepithelial lymphocytes (IEL) and lamina propria lymphocytes (LPL) or cultured in the presence of IL-2. The expression of the beta7 integrins was investigated.
Results: In situ no differences were observed in alphaEbeta7 and alpha4beta7 integrin expression in isolated IEL and LPL, whether determined by flow cytometry or by immunohistochemical staining. In gut mucosal T cell lines, alphaEbeta7 expression was significantly higher in the mucosa of patients with AS compared with controls. Alpha4beta7 was highly expressed on T cells in both groups studied. Mucosal T cells either expressed only the alpha4beta7 integrin or co-expressed the alpha4beta7 and alphaEbeta7 integrins. Almost none of them expressed only the alphaEbeta7 integrin.
Conclusion: In gut mucosal T cell lines from patients with AS an increased expression of alphaEbeta7 was observed.