Tumour necrosis factor microsatellites in reactive arthritis

The purpose was to study tumour necrosis factor (TNF)-a, -b and -e microsat ellites as potential new susceptibility markers for reactive arthritis (ReA ). Fifty-nine patients typed for HLA-B27 were studied for frequencies of TN F microsatellite alleles and compared with allele frequencies determined fr om 285 random haplotypes and 46 healthy HLA-B27-positive controls. TNFa, -b and -c microsatellite sequences were amplified by the polymerase chain rea ction, and the size of the product was defined by an automated sequencer. T he frequencies of TNFa6 and -c1 alleles were found to be increased in patie nts with ReA, whereas TNFa11 and -c2 frequencies were decreased as compared to control haplotypes. The increase in the cl allele in patients with ReA independently from HLA-B27 suggests that it might be a new susceptibility m arker for the disease. The association of ReA with other alleles was due to a linkage disequilibrium with HLA-B27.