Rheumatoid Factors in Subacute Bacterial Endocarditis—Bacterium, Duration of Disease or Genetic Predisposition?

SUMMARY

Forty-three patients with subacute bacterial endocarditis (SBE) were studied in an attempt to define what clinical features were important in the development of antigamma globulin factors during the course of their infection. Forty-seven percent showed positive latex fixation tests, and more than half showed some type of anti-gamma globulin factor during the course of their illness. A high degree of correlation between quantitative serum elevations of gamma G and positive test for rheumatoid factors was noted. However, the quantitative elevations of gamma G could not be directly related to infecting bacteria since absorption of sera with the latter produced no more than a 15% decrement in gamma G immunoglobulin. Most patients who developed positive latex fixation tests had a duration of active SBE greater than 6 weeks. An attempt was made to relate the development of a positive latex fixation test to genetic predisposition towards production of various autoantibodies. Kindreds from latex-positive and latex-negative patients with SBE showed no distinct differences in background autoantibodies to nuclear constituents, thyroglobulin, or gamma globulin. However, the most important factors in determining whether patients with SBE develop anti-gamma globulin factors appeared to be duration of infection and quantitative serum elevations of gamma G.