Abstract

Background: The incidence and characteristics of spontaneous ankylosis in the ankle of specific F₁ mice descended from two Fas-deficient strains were reported. Here the coincidence of synovial proliferation and ankylosis in the descendent F₂ mice is reported.

Aim: To clarify whether the two distinct manifestations are genetically different.

Methods: An arthropathic group of mice (MCF₂) were bred by intercrossing MRL/Mp.Fas^lpr-sap^–/sap^– and C3H/He.Fas^lpr mice. All mice were killed by bleeding under anaesthesia when they were 6 months old. Pathological grades for synovial proliferation were determined by microscopical examination. To obtain a linkage locus, the whole genome of male MCF₂ mice was scanned by using 73 microsatellite markers.

Results: Synovial proliferation was equally observed in male and female MCF₂ mice. No correlation was observed between the grades of synovial proliferation and the ankylosis occurring in the MCF₂ mice. A suggestive susceptibility locus was shown in the middle of chromosome 11. This locus was an MRL allele with a recessive inheritance mode.

Conclusion: The pathogenic mechanisms of synovial proliferation and ankylosis are genetically different. The present locus is overlapped with some loci associated with rheumatoid arthritis and with others associated with experimental arthritides.