[Significance of the serum rheumatoid factor-like substance in the induction of arthritis in the rabbit immunized with Escherichia coli].

Rabbits immunized with heat-killed Escherichia coli 0:14 for 8-10 months developed lymphocyte infiltration in the synovium at a significantly (p less than 0.05) higher rate (61.1%, 22 of 36 knees) than animals immunized for 4 months (31.3%, 10 of 32). Serum rheumatoid factor-like substance (RFLS) was positive (RAHA-titer more than 80) as early as 3 weeks after the initial treatment. After 15 weeks of immunization 90.9% (20 of 22 rabbits) of the animals were RFLS positive. Lymphocyte infiltration in the synovium of knees was observed more frequently (81.8%, 9 of 11 rabbits) (p less than 0.05) in the group with positive RFLS earlier than 8 weeks following immunization than in that with RFLS only after this period (18.2%, 2 of 11). These observations suggest that the long viability of serum RFLS and certain factors inducing early RFLS synthesis might be important in producing arthritis in rabbit immunized with E. coli.