Familial occurrence of the rheumatoid factor

The inhibition test and the latex fixation test (by the authors' modification) were both found positive more frequently in relatives of rheumatoid patients than in control groups. The authors, having assumed that a positive rheumatoid inhibition test, i.e., failure of sera to inhibit the sheep cell test (amboceptor), is due to the presence of small quantities of rheumatoid agglutinator in the euglobulin fraction, concluded from this and from the results of the capillary latex fixation procedure that increased amounts of rheumatoid factor are present in members of families of patients with rheumatoid arthritis.