Ankylosing spondylitis in monozygotic twins: studies on immunological parameters

Objective-To examine immunological parameters that might explain disease di scordance in monozygotic twin pairs with ankylosing spondylitis (AS), Methods-11 monozygotic twin pairs (nine with AS, two with undifferentiated spondyloarthropathy) were investigated. The peripheral T cell, receptor V b eta repertoire was investigated using FAGS analysis and 14 different V beta antibodies. In addition serum samples were tested for antibodies to Klebsi ella pneumoniae, Streptococcus pyogenes, Candida albicans, Proteus mirabili s, and Escherichia coli. Peripheral blood lymphocyte reactivity against a n umber of bacteria was investigated by interferon gamma ELISPOT assays. Results-Twins suffering from AS showed cellular hyporeactivity against K pn eumoniae, S pyogenes, C albicans in the ELISPOT assays compared with health y twins. In contrast with the antibody data, where no significant differenc es were observed between the two groups, AS concordant twins showed the mos t pronounced differences in their V beta repertoire on CD4+ and CD8+ lympho cytes. Conclusions-Cellular hyporeactivity of peripheral blood cells to bacterial antigens might reflect defective T cell responses allowing bacterial antige ns to persist in diseased patients. There are probably other environmental factors that influence disease concordance.